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The Role of the Biological Perspective in Psychology

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Daniel B. Block, MD, is an award-winning, board-certified psychiatrist who operates a private practice in Pennsylvania.

Main Topic Areas

Example of the biological perspective, strengths of the biological perspective, weaknesses of the biological perspective.

There are many different ways of thinking about topics in psychology. The biological perspective is a way of looking at psychological issues by studying the physical basis for animal and human behavior. It is one of the major perspectives in psychology and involves such things as studying the brain, immune system , nervous system, and genetics.

One of the major debates in psychology has long centered on the relative contributions of nature versus nurture . Those who take up the nurture side of the debate suggest that it is the environment that plays the greatest role in shaping behavior. The biological perspective tends to stress the importance of nature.

The Biological Perspective

This field of psychology is often referred to as biopsychology or physiological psychology. This branch of psychology has grown tremendously in recent years and is linked to other areas of science including biology, neurology, and genetics.The biological perspective is essentially a way of looking at human problems and actions.

The study of physiology and biological processes has played a significant role in psychology since its earliest beginnings . Charles Darwin first introduced the idea that evolution and genetics play a role in human behavior.

Natural selection, first described by Charles Darwin, influences whether certain behavior patterns are passed down to future generations. Behaviors that aid in survival are more likely to be passed down while those that prove dangerous are less likely to be inherited.

Consider an issue like aggression. The psychoanalytic perspective might view aggression as the result of childhood experiences and unconscious urges. The behavioral perspective considers how the behavior was shaped by association, reinforcement , and punishment . A psychologist with a social perspective might look at the group dynamics and pressures that contribute to such behavior.

The biological viewpoint, on the other hand, would involve looking at the biological roots that lie behind aggressive behaviors. Someone who takes the biological perspective might consider how certain types of brain injury might lead to aggressive actions. Or they might consider genetic factors that can contribute to such displays of behavior.

Biopsychologists study many of the same things that other psychologists do, but they are interested in looking at how biological forces shape human behaviors. Some topics that a psychologist might explore using this perspective include:

• Analyzing how trauma to the brain influences behaviors
• Assessing the differences and similarities in twins to determine which characteristics are tied to genetics and which are linked to environmental influences
• Exploring how genetic factors influence such things as aggression
• Investigating how degenerative brain diseases impact how people act
• Studying how genetics and brain damage are linked to mental disorders

This perspective has grown considerably in recent years as the technology used to study the brain and nervous system has grown increasingly advanced.

Today, scientists use tools such as PET and MRI scans to look at how brain development, drugs, disease, and brain damage impact behavior and cognitive functioning.

An example of the biological perspective in psychology is the study of how brain chemistry may influence depression. Antidepressants affect these neurotransmitter levels, which may help alleviate depression symptoms.

However, research on biological psychology has also disputed the idea that serotonin levels are responsible for depression, so more research is needed in this area to better understand the impact of brain chemicals on depression symptoms.

The use of brain imaging to understand how the brain and nervous system influence human behavior is another example of the biological perspective in psychology.

The Biological Perspective of Personality

The biological perspective of personality is another example of how looking at biological and genetic factors can be used to understand different aspects of psychology. The biological perspective of personality focuses on the biological factors that contribute to personality differences.

This perspective suggests that personality is influenced by genetic and biological factors. Temperament, which is the biologically-influenced pattern that emerges early in life, is one example of how the biological perspective can be used to understand human personality.

One of the strengths of using the biological perspective to analyze psychological problems is that the approach is usually very scientific. Researchers utilize rigorous empirical methods, and their results are often reliable and practical. Biological research has helped yield useful treatments for a variety of psychological disorders .

The weakness of this approach is that it often fails to account for other influences on behavior. Things such as emotions , social pressures, environmental factors, childhood experiences, and cultural variables can also play a role in the formation of psychological problems.

For that reason, it is important to remember that the biological approach is just one of the many different perspectives in psychology. By utilizing a variety of ways of looking a problem, researchers can come up with different solutions that can have helpful real-world applications.

A Word From Verywell

There are many different perspectives from which to view the human mind and behavior and the biological perspective represents just one of these approaches.

By looking at the biological bases of human behavior, psychologists are better able to understand how the brain and physiological processes might influence the way people think, act, and feel. This perspective also allows researchers to come up with new treatments that target the biological influences on psychological well-being.

Beauchaine TP, Neuhaus E, Brenner SL, Gatzke-Kopp L. Ten good reasons to consider biological processes in prevention and intervention research .  Dev Psychopathol . 2008;20(3):745-774. doi:10.1017/S0954579408000369

Moncrieff J, Cooper RE, Stockmann T, Amendola S, Hengartner MP, Horowitz MA.  The serotonin theory of depression: A systematic umbrella review of the evidence .  Mol Psychiatry . 2022. doi:10.1038/s41380-022-01661-0

Hockenbury, DH & Hockenbury SE. Discovering Psychology . New York: Worth Publishers; 2011.

Pastorino, EE, Doyle-Portillo, SM. What Is Psychology? Foundations, Applications, and Integration . Boston, MA: Cengage Learning; 2015.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

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The Biological Approach

Last updated 5 Sept 2022

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The biological approach attempts to explain behaviour as the direct product of interactions within the body.

Key assumptions of the biological approach

• There is a direct correlation between brain activity and cognition
• Biochemical imbalances can affect behaviour
• Brain physiology can affect behaviour
• Behaviour can be inherited (as it is determined by genetic information)

Evolution and the genetic basis of behaviour

Charles Darwin’s publication – On the Origin of Species (1859) – described the process of natural selection ; characteristics that are not suited to a species’ environment will die out as it struggles to survive, and with time will evolve over generations so that only adaptive characteristics remain in future offspring.

Genes are the genetic information carried by DNA in chromosomes , found within a cell’s nucleus; they are passed on through generations of a species if individuals survive and successfully reproduce. In line with Darwin’s theory of evolution, it might also follow that genes form a basis of behaviour, as both behaviour and genes appear to be heritable . An example might be aggressive behaviour, in light of obvious survival benefits such as warding off predators and competing for resources.

Nature-nurture debate

The genotype describes the genetic configuration of an individual, whereas phenotype describes the combined effects of genetic makeup and surrounding environment on behaviour. The nature-nurture debate highlights a key argument in psychology, over the relative influence of biology and environment on the characteristics of an individual; an extreme biological approach assumes that these are determined solely by nature.

Effects of brain physiology and neurochemistry

Interactions between regions of the brain help to control different functions, which biological psychologists assume to be significant in determining our actions. For instance, the occipital lobe is involved heavily in processing sight, along with the frontal lobe, which is thought to be involved in control and attention.

Electrical impulses enable an important means of internal communication that directs our behaviour, travelling around the brain and to/from the body via the nervous system . Impulses are transmitted between neurons (nerves) at synapses , junctions where neurotransmitters are released that inhibit or excite other neurons to achieve different responses. Neurochemical imbalances in the brain are often associated with abnormal behaviour – for instance, evidence suggests that imbalances of dopamine (a neurochemical linked with the brain’s natural ‘pleasure’ system) are associated with mood disorders such as depression.

The endocrine system is a slower-acting communication system that regulates the circulation of hormones , released by glands into the bloodstream. For example, cortisol and adrenaline are key hormones that facilitate the fight or flight response , a key evolutionary survival mechanism whereby the body primes itself for imminent danger (e.g. increasing heart rate, initiating sweating to cool down, dilation of pupils, sharpened sense of hearing).

Research methods used by the biological approach

Animal studies – used to investigate biological mechanisms that govern human behaviour, often where ethical guidelines would not allow human participation. Many species (e.g. rats) are thought to have a similar biological makeup to humans, such that studies’ conclusions can be generalised to humans. However, this methodology still raises ethical debate, and some argue that complex human behaviour cannot be replicated in non-human animals like rats, and thus cannot be investigated.

Case studies – can investigate normal behaviour by observing behavioural abnormality alongside corresponding changes in biology. A very early example is the apparent personality alteration observed in Phineas Gage (mid 1800s) after a railroad construction accident drastically changed his physiology by forcing an iron rod through his brain’s frontal lobe.

Drug therapy – behaviour can be manipulated by altering an individual’s biochemistry, a research method that can ultimately lead to developing drug applications to improve health and wellbeing. Initial phases of research are usually conducted on non-humans.

Scans – physiology and activity across the brain can be gauged using various techniques (e.g. MRI, PET, CAT), helping researchers to identify the functions of specific regions (known as localisation of cortical function ).

Twin/family studies are useful for investigating the heritability of behaviour. For instance, research can investigate the likelihood that both of two twins develop a characteristic, known as a concordance rate. However, these studies can be time-consuming, due to long delays often required before follow-up data is collected. It is also difficult finding a large samples of participants for twin studies.

Example : Evidence has suggested that if one identical twin (monozygotic [MZ], with near-identical genetic information to the other) develops schizophrenia, there is a roughly 48% chance of the other also developing schizophrenia, whereas this is only about 17% with non-identical twins (dizygotic [DZ], who share about 50% of their genes). Such findings support that genetics play a significant part in the disorder.

Evaluation of the biological approach

• Scanning research techniques are useful for investigating the functions of the brain: an organ with obvious involvement in our behaviour that would otherwise be unobservable.
• The approach presents the strong nature viewpoint of the nature-nurture debate.
• The experimental methods used (gathering empirical [i.e. observable] evidence) make this approach very scientific.
• The approach is considered reductionist; complex behaviour, thoughts and emotions are all equally explained by low-level biological mechanisms such as biochemicals and nerve impulses.
• Biology alone has been unable to explain the phenomenon of consciousness.
• An extreme biological approach does not account for the wide base of evidence that points to the influence of our environment (e.g. culture and society).
• Natural selection
• Endocrine System
• Hypothalamus

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Exam Tips: Research methods in the biological approach

Travis Dixon October 22, 2016 Biological Psychology

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Understanding research methodology in psychology can be difficult. Hopefully this post will help make things a little clearer. 

When understanding any topic in psychology, I like to use a basic “What-How-Why” approach. This works particularly well for research methods.

• Exam Tips: How to write a research methods essay
• Lesson idea: Understanding research methods (with worksheet)
• Biological Approach Research Methods Example Essay (ERQ)

What methods are used?

The most common research methods used in psychology are experimental, case studies and correlational studies. This is the same for biological psychology as any field.

I recommend focusing on true experiments where there’s clearly been an independent variable manipulated to create different conditions of the experiment. To save the issue of having to classify different studies and types of experiments based on their nuanced definitions and overlaps.

• Serotonin ( Passamonti ), Cortisol ( Buchanan and Lovallo ), etc.
• Case studies (e.g. HM’s case study)
• Correlational studies:  Socioeconomic status and brain (e.g. Karl ).

The use of technology is not a research method on its own, but is used as part of an experiment, case study or correlational study. Similarly, meta-analyses or twin studies are also not technically “research methods” according to the IB. See the following image from the IB Psychology’s FAQs document for more explanation.

(IB Psychology FAQs, pg.8. MyIB).

How are they used?

It’s important that you can describe in detail the methodology used when adopting one of the research methods. You also need to link it specifically to biological factors. You can begin with a general summary. For example, when explaining experiments you would explain how researchers manipulate an IV and may randomly allocate participants to groups before measuring the effects of this on the DV. To show full understanding you should go deeper and link this to biological psychology. For example, you can explain how experiments are used to study hormones by manipulating the levels of hormones in the body and seeing how this affects cognition, the brain, or behaviour.

Correlational studies involve the measuring of two co-variables without focusing on an IV and a DV. In biological psychology, at least one of the co-variables will be biological, such as brain volume or levels of hormones.

Case studies are conducted on participants when studying the brain and behaviour when patients have interesting and unique brain damage and the influence this has on behaviour is studied. Data is gathered using multiple methods, including brain scans, questionnaires, interviews and observations.

Teacher Tip: I used to begin my course with research methods like most people. I later learned that this was like building a house by starting with the roof. It was much easier to wait until later in the course when the students understood the studies, to then go back and use these as examples of how and why research methods are used in various fields of psychology.

I teach a unit on Quantitative methods that covers all this content in IB Psych. I do this right before the IA.

Why are they used?

Again, you can begin with a general summary of the methodology that researchers follow when using any of these methods. It’s important to understand the general reasons behind using a particular method.

For example, true experiments are used because they allow cause and effect conclusions to be drawn. This is because they control extraneous variables, ensuring only the IV is having an effect on the DV. However, this explanation could apply to any field, so we need to link it to biological psychology. In this case, the IV is often a biological factor (neurotransmitter, hormones or even genetics) and the effects are measured on a dependent variable (a behavior or perhaps brain function). Now the link to biological psychology is clearer.

The important thing to remember is to link the ‘why’ to the biological factors. What is it about the biological level of analysis that makes this a useful research method to use. For example, why experiments? (think about why animal experiments are common). Why are case studies like HM’s valuable to study the brain (especially before modern brain imaging techniques were invented)?

WHAT? HOW? WHY? BUT… I like using this simple framework when approaching any topic in psychology. Whether it’s teaching the course, studying for exams or planning an exam answer, this simple framework can work.

Travis Dixon is an IB Psychology teacher, author, workshop leader, examiner and IA moderator.

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• Spring 2024 | VOL. 36, NO. 2 CURRENT ISSUE pp.A4-174
• Winter 2024 | VOL. 36, NO. 1 pp.A5-81

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Biological Psychology: An Introduction to Behavioral, Cognitive, and Clinical Neuroscience, Third Edition

• Samuel T. Gontkovsky , Psy.D.

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The multidisciplinary nature of biological psychology as a field provides a unique forum for the interaction and collaboration of professionals unparalleled in other areas of clinical and scientific study. Indeed, the scope of biological psychology transcends all levels of organismic development, from the molecular level to the cellular level, the systemic level, and the social level. Contributing to the advancement of this discipline, from both a theoretical and an empirical perspective, is a diverse representation of investigators trained in the areas of anatomy, anthropology, behavioral medicine, biochemistry, clinical neuropsychology, endocrinology, genetics, molecular biology, paleontology, psychiatry, and psychophysiology to name but a few. Working together, these professionals study the structural and functional aspects of behavior across species, explore the developmental processes of biology and behavior across the life span, and utilize findings to formulate practical applications that promote human health.

The comprehensive nature of the field and the diversity of professionals encompassed by the arch of its umbrella pose a particular challenge, however, in the drafting of a textbook that not only can be appreciated, but easily understood, by the representative populace of biological psychologists as well as the students desiring to acquire an understanding of this area of study. The third edition of Biological Psychology serves as an excellent source for bridging the gap between the multitudes of specialties that constitute this discipline. The text consists of 18 chapters divided into five primary sections. A short introductory chapter, which provides a basic overview of the field, is followed by a section focusing on the biological foundations for behavior. Chapters in this section, which provide the requisite foundation for understanding the remainder of the text, introduce readers to organisms at cellular level, discussing the primary topics of functional neuroanatomy, neurophysiology, psychopharmacology, and hormones.

Subsequently, the authors move to a presentation of evolutionary and developmental aspects of the nervous system. Comparative methods are discussed sufficiently to allow for an appreciation for the manner in which studying the various invertebrate species (e.g., aplysia), with relatively simple neural networks, has lead to a more thorough understanding of the enormously intricate nervous systems housed by the vertebrate species (e.g., human). Furthermore, emphasis is placed upon the notion that neural networks are shaped not only by intrinsic factors, such as chromosomal aberrations, but also by extrinsic factors, including environmental experience.

The focus of section three is that of sensation and movement. Chapters review the concepts of somatosensory, auditory, visual, vestibular, olfactory, and gustatory perception as well as motor control and plasticity. While ample attention is given in this section to the anatomical and physiological mechanisms involved in perception and movement, the authors remain sensitive to the role of learning in these behaviors and the manner in which environmental elements influence such systems. Regulation of behavior is presented in section four. Primary topics discussed include sex, homeostasis, and biological rhythms. In this section, as in section three, the authors provide an evolutionary, developmental, and comparative perspective of the issues and overview not only the normal but also the possible abnormal variants (e.g., congenital adrenal hyperplasia, anorexia nervosa, and somnambulism) of these processes.

Emotions and psychopathology comprise the heart of section five. An overview of competing theories (e.g., James-Lange and Cannon-Bard) regarding the link between subjective psychological phenomena and the activity of the visceral organs controlled by the autonomic nervous system initially is presented followed by the role of facial expressions in the communication of emotional states. An excellent discussion is provided concerning the utilization of relatively new functional neuroimaging techniques to investigate specific regions of the brain that are particularly active during various emotional states. Special attention also is given to the neural circuitry underlying violence and aggression as well as to the relationship between stress and immunosuppression. The major psychiatric disorders are reviewed from both a social and a biological perspective.

The text concludes with a section devoted to cognitive neuroscience, with particular emphasis on the biological perspectives and neural mechanisms of learning and memory. With citations ranging from classic reports of early pioneers, such as that of Ramón y Cajal 1 suggesting that during the processes of development and learning neuronal extensions of axons and dendrites occur to develop new connections within the brain, to that of more contemporary investigators, including the findings of Shors, Miesegaes, Beylin, Zhoa, Rydel, and Gould 2 suggesting that neurogenesis in the hippocampus may be required for trace conditioning of the eye-blink response, the authors bring together in a comprehensive yet concise fashion more than 100 years of research in this area.

In addition to an inclusive glossary of terms, the work includes an afterword discussing the plasticity of the ever-changing brain as well as a nice appendix providing a basic overview of molecular biology. Throughout, the text is richly illustrated with drawings, photographs, figures, and tables that complement the written text. With the exception of a few minor shortcomings concerning the topic of psychopharmacology (Chapter 4), the text is integrative and inclusive, providing the requisite information necessary for a methodical understanding of the field.

From a didactic perspective, the text is ideal for an advanced doctoral level course in the area. The book is probably far too complex, however, for utilization at the undergraduate level, and arguably, incorporates details from various fields that may be beyond the digestive comprehension of some graduate students who lack sufficient background in these areas of study. Although the authors provide an introductory overview at the beginning of each chapter, a relatively rapid progression from basic concepts to more complex issues takes place. A CD-ROM, entitled Learning Biological Psychology, is provided with the text that provides for students multiple study questions, animated tutorials, videos, and interactive testing to enhance learning and retention. Individuals with a basic, yet solid, foundation in biology, chemistry, and psychosocial behavior, however, should be capable of grasping the vast majority of presented material.

By Mark R. Rosenzweig, S. Marc Breedlove, and Arnold L. Leiman, Sunderland, Massachusetts, Sinauer Associates, 2001, 651 pages, ISBN 0-87893-709-9

1 Ramón y Cajal S: La fine structure des cebtres nerveus. Proceedings of the Royal Society of London. Series B: Biological Sciences 1894 ; 55:444–468 Google Scholar

2 Shors TJ, Miesegaes G, Beylin A, et al.: Neurogenesis in the adult is involved in the formation of trace memories. Nature 2001 ; 410:372–376 Crossref , Medline ,  Google Scholar

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Biological Psychology

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a really good textbook for supporting the teaching of Psychology

Mistakes in the labeling of some diagrams in the text.

This was an interesting book suitable for use at level 4, so will recommend to students

Extremely useful as a reference book, and for learning the fundamentals of the biological theories.

Excellent text book that is easy for the students to read. It looks in detail at the biological aspects and introduces the reader to biological psychology using case studies.

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Is psychodynamic same as psychoanalytic?

The words psychodynamic and psychoanalytic are often confused. Remember that Freud’s theories were psychoanalytic, whereas the term ‘psychodynamic’ refers to both his theories and those of his followers, such as Carl Jung, Anna Freud, and Erik Erikson.

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What is Freud’s psychosexual theory?

Sigmund Freud proposed that personality development in childhood takes place during five psychosexual stages, which are the oral, anal, phallic, latency, and genital stages.

During each stage, sexual energy (libido) is expressed in different ways and through different body parts.

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What Is object permanence in Piaget’s theory?

Object permanence means knowing that an object still exists, even if it is hidden. It requires the ability to form a mental representation (i.e. a schema) of the object.

The attainment of object permanence generally signals the transition from the sensorimotor stage to the  preoperational stage of development .

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Pamoja Student Guide to IB Psychology

Chapter 4: biological approaches to understanding behaviour, chapter outline, 1. the rise of the biological approach in psychology, 2. research methods of the biological approach.

2.1 Correlational Studies

2.2 Case Studies

2.3 experiments, 2.4 ethics and research methods of the biological approach, 3. the brain and behaviour, 3.1 techniques used to study the brain in relation to behaviour, 3.2 localisation, 3.3 neuroplasticity, 3.4 neurotransmitters and their effect on behaviour, 3.5 assessment advice, 4. hormones, pheromones and behaviour, 4.1 hormones and their effect on behaviour.

4.2 Pheromones and Their Effect on Behaviour

4.3 Assessment Advice

5. genetics and behaviour, 5.1 genes and behaviour, 5.2 genetic similarities, 5.3 evolutionary explanations for behaviour, 5.4 assessment advice, 6. the role of animal research in understanding human behaviour, 6.1 can animal research provide an insight into human behaviour.

6.2 The Value of Animal Models in Research into the Brain and Behaviour

6.3 The Value of Animal Models in Research into Hormones and/or Pheromones

6.4 The Value of Animal Models in Research into Genetics and Behaviour

6.5 Ethical Considerations in Animal Research

6.6 Assessment Advice

Essential Questions What research methods do psychologists adopting a biological approach use to study behaviour? What techniques do they use to study the brain? How do the brain’s neural networks change over time and in response to learning and the environment? How do neurotransmitters affect behaviour? How do hormones and pheromones influence behaviour? How do genes influence behaviour? How does evolutionary psychology explain behaviour? What is the role of animal research in understanding human behaviour?

Myths and Misconceptions

Psychological research 'proves' hypotheses.

Never use the word 'prove' or 'proven' in your writing. Psychological research tests hypotheses and explains behaviour. Use 'supported', 'demonstrated that', but nothing is ever 'proved' or 'proven.'

The brain is far too complex to be studied in a meaningful way.

Innovative research in both the medical and biological psychology fields has made immense progress in revealing how the brain works and how it affects behaviour. In particular, technological advances in being able to generate images of the brain have enabled scientific research in this area to progress at a rapid pace. Have a look at the research being carried out at King’s College London into infant brain development or at the Human Genome Project.

One day, it will be possible to use genetics to explain a substantial amount of human behaviour.

Although a considerable amount of research into genetically inherited behaviour has been conducted, scientists are still unable to state with certainty the degree to which behaviours such as aggression or disorders such as major depressive disorder are predominantly influenced by genes. Indeed, as human behaviour is so complex, working out which genes are responsible for different behaviours is a phenomenally difficult undertaking for scientists. Moreover, determining how far genes influence behaviour is further complicated by the influence of external environmental factors such as stress and type of upbringing on both our behaviour and our genetic makeup.

Pheromones can influence our behaviour without our awareness.

Some researchers have claimed that pheromones secreted from our body can influence the behaviour of others. The perfume industry promotes this idea, which is strange as pheromones are odourless! However, many researchers have questioned the existence of human pheromones in humans and argue that pheromone research in humans is based on flawed assumptions. The evolutionary biologist Tristram Wyatt had written extensively about this, and his TED talk on the subject is very interesting.

During the 19th century, a quiet revolution in assessing how brain and behaviour are linked was taking place in the consulting clinics of such physicians as Paul Broca in France and Carl Wernicke in Germany. By adopting a systematic analysis of patients with language difficulties, these researchers helped to establish the scientific study of brain localization. Broca’s analysis of speech production deficits in his patients along with post-mortem brain analysis of some of these patients helped him to isolate a left frontal brain area that is responsible for the generation of language.

Today, this area is known as Broca’s area. Taking the same approach, Wernicke demonstrated that an area of the temporal lobe called the posterior superior temporal gyrus caused deficits in speech comprehension and the ability to produce meaningful language. This area is now known as Wernicke’s area. The work conducted by Wernicke and Broca and other researchers at the time led to the acknowledgement of the importance of studying brain-damaged individuals. This has resulted in the case study approach becoming a significant research tool in modern biological psychology and has led to the establishment of a discipline in psychology called clinical neuropsychology.

Researchers like Broca and Wernicke were at the forefront of the 19th-century movement towards a more systematic, scientific way of investigating the natural world. One of the most famous proponents of this approach was Charles Darwin, who, in producing his theory of evolution, had himself documented thousands of observations around the world to provide evidence for his theory. At that stage, science was a long way from understanding evolutionary mechanisms down to the genetic level as a result of the lack of scientific technology. However, scientific advances in research and technology eventually revealed that genes formed the building blocks of evolutionary mechanisms. In the last couple of decades, the role that genes play in behaviour has led to the establishment of evolutionary psychology and also research into how far behaviour such as intelligence may be inherited.

Significant advances in brain imaging technology have helped to propel the legacy of researchers like Broca and Wernicke even further forwards with the use in the modern psychology of techniques that can image the live brain. Not only have such technologies reinforced findings from neuropsychological research into localization they have also enabled researchers to assess cognitive processes such as memory and thinking in individuals without brain damage. Consequently, such research has enabled researchers to make significant advances in understanding the brain and behaviour relationship.

Furthermore, in conjunction with the medical field and also advances in medical science, biological psychologists have also increased our understanding of how hormones and pheromones affect behaviour.

Researchers who take a biological approach to understanding behaviour believe that all human behaviour has a biological basis. This is not to say they believe that it is only biological, but that there is a relationship between the human body and especially the brain (the structure and processes of the human nervous system) and human behaviour. Moreover, because the nervous systems of many animals are similar in their structure and processes to that of humans, biological psychologists use animals in research to gain understanding about human behaviour.

The most common research methods used in the biological approach are:

Correlational studies

Case studies

Experiments

Ask Yourself What difficulties do you think psychologists face when studying the brain?

2.1 Correlation Studies

Correlational research measures the relationship between two variable that are themselves not manipulated. Correlational studies in the biological approach focus on finding a relationship between a behaviour and inherited traits. This relationship is called the amount of heritability that a behaviour has. Correlational studies will usually be twin studies and adoption studies, which are important sources of information about the link between genetics and behaviour. Such studies are useful because they can suggest how much different behaviours are the result of genes and how much is down to environmental influences. The likelihood of twins or siblings sharing a genetic trait is measured by the concordance rate, which is expressed as a decimal or a percentage. So if one of two identical twins has depression, the likelihood of the other twin also suffering depression can be expressed as a decimal from 0 to 1, with 1 being perfect certainty that the other will have it, or as a percentage chance of 0-100%. A concordance rate of 0.7 is considered very high for many behaviours. This means that there is a 70% chance of the other twin having depression.

Apart from twin and adoption research, in biological psychology correlational studies are also used to show relationships between behaviours and activity in certain brain areas.

Focus on Research – a twin study (correlational study)

Later in the course, you will look at explanations for major depressive disorder (MDD). One of the biological explanations is that MDD is at least partially genetic, and therefore is inherited. To test the heritability of MDD, Kendler et al. (2006) conducted a huge study in Sweden, with personal interviews of 42,161 twins, including 15,493 complete pairs, from the national Swedish Twin Registry. The researchers estimated the heritability of MDD at 35-40%, with heritability being significantly higher in women than men (42% to 29%).

They found that twin pair resemblance for lifetime MDD was not predicted by the number of years the twins had lived together in the home of origin or by the frequency of current contact. This tends to support the idea of a biological, rather than a sociocultural (environmental) explanation for MDD.

A case study involves the in-depth and detailed study of an individual or a particular group in order to obtain a deep understanding of behaviour. In the biological approach, this method is particularly favoured in the field of neuropsychology in order to establish a relationship between the brain and a specific behaviour. For example, a psychologist studying the biological foundation of amnesia would analyse the behaviour of a patient and correlate any deficits in memory with a detailed biological analysis obtained through brain imaging. Such research can help inform existing biological theories of memory and indeed could lead to the development of new theories. Case studies can go on for many years (longitudinal case studies) and often have within them several different methods, such as observations, use of brain imaging techniques and interviews.

Focus on Research – a case study – H.M.

One of the most famous amnesiac patients in the history of psychology was Henry Molaison and a detailed outline of his case study and subsequent legacy is provided by Squire (2009). You will see him referred to as H.M. in many books and articles and this is due to the requirement of participant confidentiality. However, very rarely, some research participants and/or their partners/family are happy for the full name to be known and one example is the case study of Clive Wearing in Chapter 5.

Born in 1926, Henry Molaison had been hit by a cyclist when he was seven and from the age of ten then started to have epileptic seizures that subsequently started to worsen as he neared adulthood. By the time he was twenty-seven, these seizures were so crippling that he underwent surgery for a bilateral medial temporal lobe resection. This involved cutting out significant portions of Henry’s brain in the temporal lobe area to try to control the seizures. However, the surgery resulted in severe anterograde amnesia, a type of amnesia that leads to deficits in encoding new information into the brain. It should be noted that when Henry had this operation, knowledge about the brain’s functions was limited hence the dramatic consequences of such an operation were little understood at the time.

Henry’s legacy in terms of our knowledge about memory is highly significant because as a result of extensive research with him up to his death in 2008, Henry had contributed a wealth of data about his memory function. Firstly, given that his short-term memory was normal, this demonstrated that the short- and long-term memory systems in the brain must, to some extent, be separate otherwise Henry’s brain damage would also have affected short-term memory processing. This finding reinforced the ‘separate stores’ claims of the multi-store model of memory that you will study in Chapter 5.

However, what was intriguing about Henry’s case, and indeed other similar cases of anterograde amnesia, is that it demonstrated that there are different types of long-term memory. Henry’s brain damage specifically targeted episodic memory and he was, therefore, unable to form new memories of any event experienced after the surgery and this continued to the end of his life. However, he was able to form new procedural longterm memories. Procedural memories are those memories which are automatic such as knowing how to drive. This type of knowledge does not start out as automatic because clearly skills such as driving must be learned. These skills develop over time, however, and activities such as driving become easier and more automatic if we practise them regularly.

Despite his extensive brain damage, Henry could form new procedural memories on activities such as a pursuit rotor task in which a participant tracks a moving object on a screen with a cursor. This task requires precision and must be practised regularly to gain expertise in the task. Henry was able to show that he could develop these skills even though he could not remember previous practice sessions due to his episodic memory deficit. Such testing with Henry and other amnesic patients led memory researchers to understand more about how memory processing is carried out in the brain and in particular to understand that skill memory does not require the use of medial temporal lobe systems to work effectively.

You can use this case study of Henry Molaison as a key study in both the brain imaging techniques and the localization of function section later in this chapter.

Experiments are used to measure the effect of an independent variable (IV) on a dependent variable (DV). They can be conducted under either artificial or natural conditions. In a true experiment, which tries to determine a cause and effect relationship between the IV and the DV, the IV is manipulated, the DV is measured and all extraneous variables that might affect the outcome of the experiment are carefully controlled, often by conducting such an experiment in a laboratory. The participants are randomly allocated to groups and the relationship found between the IV and the DV is a cause and effect relationship.

Quasi-experiments are experiments where the participants are allocated to groups by precharacteristics, such as day-shift or night-shift, class in school, ability in maths, gender, ethnicity, age, etc. There is sometimes, but not always a manipulated IV and control of other variables, but because of the non-equivalent groups, the relationship that is found is correlational. Quasi experiments and true experiments are common methods in biological psychology. Maguire’s study that you will read about later in this chapter is an example of a quasi-experiment that did not have a manipulated IV.

Experiments often involve non-human animals because they are extremely difficult to study in their natural habitat. As, unlike humans, animals do not guess the purpose of the experiment, results gained from animal research are free of participant expectations. Nevertheless, many people would argue that experimenting on animals is also unethical, which will be discussed later.

Focus on Research – experiment – Antonova et al. (2011)

Antonova et al. (2011) followed up on results from animal research that showed that a neurotransmitter called acetylcholine (ACh) acted in the brain to aid spatial memory, and that this action could be reduced or prevented by the chemical scopolamine. They tested twenty men with an average age of 28 years in a virtual reality maze. Everyone was randomly allocated to either a scopolamine injection group or a saline injection group (placebo/control group). Then their brains were scanned individually using a functional magnetic resonance imaging (fMRI) scan while they engaged in the task of finding their way around the maze. ACh acts mainly in the area of the hippocampus, which is specifically related to memory, especially spatial memory.

After one trial, the participants went home and returned 3-4 weeks later, were injected with whichever solution they did not have before and were scanned again. Neither the participants nor the researcher knew who was in which group. This sort of design is common in experiments and is called a ‘randomized double-blind cross-over design.’ It is well enough controlled to show cause and effect, rather than just correlation.

Scopolamine reduced the activity in the hippocampal area and the participants in the scopolamine condition also made more errors than those who received the placebo. This shows that scopolamine decreases the ACh action in the brain, confirming that ACh is associated with spatial memory in adults as well as in non-human animals.

Among the first human subject research experiments to be documented were vaccination trials in the 1700s. In these early trials, physicians used themselves or their family members as test subjects. For example, Edward Jenner (1749–1823) first tested smallpox vaccines on his son and the children in his neighbourhood. Clearly, such an approach would not be permissible today. Indeed, for both medical and psychological research, ethical guidelines have been drawn up to protect research participants. The guidelines that psychologists follow are revised regularly by groups monitoring psychological research worldwide. Two sets of these guidelines for research with human participants are those published by the American Psychological Association (APA) and the British Psychological Society (BPS), who have also published guidelines for studies using animals. They are long documents that you do not need to read in detail, but the main point is that they have been considerably strengthened since some of the classic studies that you read about on the course were carried out.

In human research, the researchers have to ensure that the following guidelines have been met:

the participants must have given informed consent

they should not be deceived, or any deception necessary for the validity of the findings should be minimal and revealed at the debrief

confidentiality must be maintained

they should be debriefed after the study

they should be allowed to with draw themselves and their data at any time

they should not be harmed psychologically or physically

In the UK, a government licence is needed to carry out animal research, and, the BPS has identified the ‘3 Rs’ of animal research. These are to:

Replace animals with other alternatives.

Reduce the number of individual animals used.

Refine procedures to minimise suffering.

We consider the ethics of animal research later in this chapter.

Ethical considerations are part of the planning and carrying out of research. They also apply to the use of data and publication. A question on ethical considerations is not requiring you to answer with a critique of the most unethical study you know, but rather to put yourself in the researcher’s place and consider the one or two prime concerns they will have had before, during and after the study. How could they keep the participants’ identities and data confidential? How could they ensure that the participants really understood the information on the informed consent sheet? How could they protect their participants from any stress while under experimental conditions? Think of Antonova et al.’s experiment (above); how could they ensure that the participants did not become too disturbed by being injected with an unfamiliar chemical and having their brain scanned?

Case studies taking a biological approach often use participants who may not be able to make an informed decision about whether to take part in a research study or not. As a consequence of this, a partner or family member usually gives consent instead. Clearly, this raises ethical issues about participants being used in research who do not have the mental capabilities to make a reasoned decision about their participation.

The development of advanced modern technology has allowed researchers to build a more accurate understanding of how our brains work. These technological methods include the encephalogram (EEG), magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI) and positron emission tomography (PET). Although all of these techniques ultimately have the same goal in that they aim to produce coherent representations of the brain, they do differ in the type of image produced: MRI scans can only show brain structure and therefore produce static images, while EEG shows brain activity, and PET and fMRI can show structure and also brain activity as it changes over time.

MRI scans represent an advancement in technology because they are able to produce static 3-D images of the brain. MRI scanners use a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body, including the brain. This technique is used to find problems such as tumours, bleeding, injury, blood vessel diseases or infection. Physicians also use the MRI examination to detect brain abnormalities in patients with dementia, a disorder that can cause confusion or memory loss. It has a high sensitivity for detecting the presence of, or changes within, a tumour. In addition, MRI scans are highly useful to neuropsychologists studying brain-damaged individuals because they have the advantage of being more detailed and in 3-D format hence localization of damage is more precise. This could be critical in determining how far small brain areas are involved in particular cognitive processes. One of the limitations of MRI scanning is that people with heart pacemakers, metal plates or screws in their bodies may not be scanned. This could, therefore, mean the loss of potential participants in psychological studies. Although this issue would not be a large-scale problem, it may become problematic if a patient with a unique psychological deficit not previously recorded could not be scanned to assess how their brain damage correlates with their psychological difficulties. Also, some people suffering from claustrophobia, people with dementia and children may find it difficult to tolerate the procedure. If people move during the scan, the images are unclear and difficult to interpret reliably.

Focus on Research - example of a study using MRI scans

Maguire et al. (2000) used MRI scans to compare the brains of licensed London taxi drivers, who have to remember a map of the streets of London in order to gain their licence, to a control group who did not drive taxis. The results showed that there was a significant difference in the size of various parts of the hippocampus of taxi drivers: the posterior hippocampus was larger in taxi drivers (especially on the right side), whereas the anterior hippocampus was larger in control subjects. The volume of the hippocampus also correlated with how long the subject had been a taxi driver. This evidence supports the theory that the posterior hippocampus in each side of the brain stores a spatial representation of the environment and is ‘plastic’, responding to the individual’s needs in response to their environment. This study also provides evidence of localization by illustrating specific brain locations dedicated to spatial mapping of the environment. (See below in Section 3.3 Neuroplasticity for full details of Maguire’s study).

fMRI is non-static brain imagery that uses magnetic resonance imaging to measure the tiny metabolic changes that take place in an active part of the brain. When neurons in a particular region are active, more blood is sent to that region. The fMRI machine maps changes in the brain’s metabolism (chemical changes within the cells) and uses radio waves and magnetic fields to generate a 3-D time map to show precisely which parts of the brain are active during a wide range of tasks. As well as investigating the correlation between behaviour and brain activity in certain areas, fMRI scans are also used to help assess the effects of stroke, trauma or degenerative disease (such as Alzheimer’s disease) on brain function. The medial temporal lobe area, which includes the hippocampus and amygdala, has been investigated in patients with Alzheimer’s disease. With the use of fMRI scans and post-mortem brain studies, cognitive neuroscientists have identified that this is the first area of the brain to show damage in this disease.

Antonova et al. (2011) used fMRI scans to detect neural activity in the hippocampal area (see Section 2.3, above).

PET scanning is a type of nuclear medicine imaging. Nuclear medicine is a branch of medical imaging that uses small amounts of radioactive material to diagnose and determine the severity of a variety of brain diseases, including cancers and neurological disorders. A radioactive substance is injected into the patient. This is usually a form of sugar that produces measurable gamma rays as it is metabolized in the brain. A PET scan detects these rays and turns them into computer images of brain activity. These scans are used to examine functions such as blood flow, oxygen use and sugar (glucose) metabolism, to help doctors evaluate how well the brain is functioning.

Because PET scans are able to pinpoint molecular activity within the body, they offer the potential to identify a disease in its earliest stages. They are useful for showing abnormalities in brain activity levels in diseases that do not show structural changes until much later, like Alzheimer’s disease. Though less precise than fMRI scans, for example, they are a useful tool in early diagnosis of brain disease.

In psychological research, PET scans have proved highly useful in monitoring blood flow changes whilst participants perform tasks linked to a wide range of cognitive abilities. This has enabled researchers to detect which brain areas are more active when participants perform various aspects of psychological tasks.

Focus on Research - example of a study using a PET scan - Tierney et al. (2001)

Tierney et al. (2001) carried out a case study on a 37-year-old male patient they referred to as M.A. While participating in a language study that involved having your brain scanned with MRI, researchers noticed that M.A had a lesion in the left hemisphere of the brain. This area of the brain is responsible for our speech and language. The lesion probably developed when he was two years old and he suffered from encephalitis (an uncommon but serious condition in which there is swelling in the brain).

It’s logical to assume that if the language areas of the brain were damaged before M.A could learn to talk or read fluently, then he would suffer from speech and language problems. However, this was not the case and M.A’s language skills had developed normally. In fact, he was bilingual – he spoke English and also used American sign language (ASL) because both of his parents had severe hearing problems. He used ASL at home and spoke English normally with other people.

Tierney et al. hypothesized that this could be because other areas of M.A.’s brain had taken over the function of speech production to compensate for the damaged speech areas in the left hemisphere. To test this, M.A. was compared with 12 bilingual (English and ASL) participants. PET scans were used when the participants were participating in speech tasks. The speech tasks involved the participants simply recounting an event or a series of events in detail.. Unlike most sign language users, M.A.’s right hemisphere was highly active, suggesting that this hemisphere had probably taken over speech production when the left hemisphere was damaged. This type of change is evidence of neuroplasticity. For example, some neural connections become stronger when a particular skill is practiced, such as juggling (see Draganski et al., 2004, in Section 3.3 below).

In M.A.’s case, the researchers concluded that his brain structure had been changed in the right hemisphere, with more connections than normal in his right frontal lobe to allow him to produce language, possibly at the expense of other skills normally localized in the right hemisphere.

Neuroplasticity is not just a feature of recovery after a brain injury because non-injured brains also undergo such neural network rearrangement as a result of influences from the environment. The fact that we do not live in a vacuum and interact on a daily basis with various aspects of the environment shows the fundamental neuroplasticity that must be occurring in the brain in order for us to adapt to life’s demands.

Localization of function refers to the theory that the mechanisms for thought, behaviour and emotions are located in different areas of the brain. To what extent certain functions are located in their own areas, and activity in this area can therefore be seen as evidence of a behaviour, thought or feeling, is the subject of localization of brain function.

There is a long history to the theory of localization of function in the brain. The concept is directly traceable to the ideas of a German physician, Franz Josef Gall (1758–1828), who introduced phrenology – the science (now seen as a pseudo-science) of inferring a person’s behaviour from the shape of their skull. While this has been discredited, the assumption that certain parts of the brain are responsible for specific behaviours is still valid.

As mentioned in the introductory section of this chapter, the French neurologist Paul Broca located the ability for speech production in the left frontal lobe, a region that came to be known as Broca’s area, as early as 1861 (Broca 1861a, 1861b). Given that the scientific techniques available to physicians like Broca to study the brain were limited at the time, the only recourse to examine the location of brain damage was to wait until a patient died in order to perform a postmortem examination.

One of Broca’s most widely cited case histories is that of Louis Leborgne who was 51 when they met and had been admitted to hospital suffering from gangrene. The patient earned the nickname of ‘Tan’ because this was the only word he could produce. He was also paralysed down the right side of his body due to what is believed to be a left hemisphere stroke. Leborgne died only a few days after meeting Broca for his initial assessment and Broca therefore performed an autopsy that revealed a left frontal lobe lesion. This therefore confirmed Broca’s assertions that this area of the brain was significantly involved in speech production and damage in this location can result in the speech production deficit known as Broca’s aphasia.

The investigation of Louis Leborgne highlights the value of the case study, as well as the autopsy in psychological research, and indeed the case study approach has formed the cornerstone to localization of function research ever since Broca’s pioneering studies of brain-damaged patients. However, recent modern advances in brain science with regard to neuroimaging technology have complemented the case study approach. In an ironic twist of fate, Leborgne’s preserved brain was subjected to brain imaging over 140 years after his death in a recent study by Dronkers et al. (2007). This study was able to demonstrate in more intricate detail the extent of Leborgne’s brain damage and served therefore as a neat illustration of the virtues of brain imaging technology being used in conjunction with patient case studies and autopsies.

Limitations of the localisation approach

Although adopting a localization approach in the quest to understand the brain has undeniably meant that scientific knowledge about the brain and behaviour is currently very advanced, other researchers have urged caution in adopting what they feel is a ‘jigsaw’ type perspective of the brain. The complexity of cognitive processes in terms of how they interact and influence each other cannot be ignored hence more holistic accounts of how the brain works should be used in conjunction with the localization approach. Karl Lashley, an eminent neuroscientist, was an early champion of a more holistic viewpoint of brain function and, in the 1950s, demonstrated the validity of this in a study with rats who had undergone lesioning. The rats in this study learned to navigate mazes and Lashley found that if he removed varying amounts tissue in the cortex of different rats in different brain areas (sometimes up to 50%), this did not affect their learning of the maze. This study, therefore, indicated that memories were widely distributed throughout the cortex and not localized to a particular area. Lashley’s fame in the neuroscience field led other researchers to also adopt an anti-localization approach, but research has since reinforced the idea that there are many specialized brain areas for different processes. Lashley and his supporters were misled in the sense that very complex tasks like learning a maze are going to use a large number of different neural networks in order to deal effectively with the task and this is why large scale lesioning (destruction of certain areas of the brain) in the rats did not impair the rats’ maze navigation skills.

Other researchers have also criticized the idea of localization because it implies that specific brain areas are specialized for particular processing and that other brain areas cannot, therefore, take over their functions. However, research into the brain’s adaptive and flexible capabilities has challenged this more static view of brain function and in the next section you will read more about these ideas and learn about studies that have demonstrated the extent to which the brain shows plasticity.

Both Maguire et al. (2000) and Draganski et al. (2004) may be used for localization of function (see below).

Ask Yourself What are some of the challenges of researching people with brain damage?

Neural networks

The examples above all demonstrate that many brain functions are localized in their own specific parts of the brain. However, the brain is far from ‘static’ because research has shown that complex neural networks can also be modified and changed in a process known as neuroplasticity . This process is of particular significance in young children during their early brain development. The very rapid development of new neural networks is essential early in life as a considerable period of learning occurs at this stage.

Earlier, you encountered the study by Maguire et al. (2000) which demonstrated how repeatedly encountering the same environmental information on a regular basis over time leads to significant neural network changes in order to accommodate such environmental information. Maguire et al.’s research clearly shows how environmental demands can alter neural networks so that they become more adapted to cope with specialized tasks.

You can use Maguire et al.’s study and Draganski et al’s (2004) research as key studies in this section on neuroplasticity, just as you can in the section on brain imaging techniques and MRI scans, and the section on localization (above).

Focus on Research – neuroplasticity and neural networks - Maguire et al. (2000)

From the results of previous research, mainly on animals, Maguire et al. believed that there may be a correlation between spatial memory and the size and density of the neural networks in the hippocampus, suggesting localization of this function (as well as neuroplasticity and the growth of neural networks). They conducted the following quasiexperiment to investigate this the ability of the brain to change in terms of volume of grey matter dependent on learning and experience.

The participants were 16 healthy, right-handed male licensed London taxi drivers who had passed ‘The Knowledge’, a test of spatial memory. The age of the sample ranged from 32- 62 years with a mean age of 44. They had all been taxi drivers for at least 18 months, with the most experience being 42 years of taxi driving.

The participants were placed in an MRI scanner and their brains were scanned. The focus of the scan was to measure the volume of grey matter in the hippocampus of each participant and then to compare it to the scans of the control group. The grey matter was measured using voxel-based morphometry (VBM) which focuses on the density of grey matter and pixel counting. The taxi drivers’ MRI scans were compared with pre-existing MRI scans of 50 healthy right-handed males who were not taxi drivers.

The researchers found that the posterior area of the hippocampi, especially the right hippocampus, of the taxi drivers showed a greater volume of grey matter than that of the controls, who had increased grey matter in their anterior hippocampi compared to the taxi drivers. They also carried out a correlational analysis and found that the growth in the right posterior hippocampal neural networks showed a significant positive correlation to the length of time spent as a taxi driver.

They concluded that the posterior hippocampus may be linked to spatial navigation skills built up via learning and experience. The correlational analysis of time spent as a taxi driver linked to increased volume of hippocampal grey matter lends validity to the idea of neuroplasticity due to learning and experience, and counters the argument that the taxi drivers may coincidentally have had larger than usual hippocampi.

Neural pruning

Not all of the neural changes will be needed as a child gets older so child development is not only characterized by rapid neural growth but also by significant neural pruning (reduction in density) as some neural pathways in the brain are no longer needed. It was thought that such widespread pruning only occurs in early childhood but research has shown that during adolescence another extended period of pruning occurs, and indeed our brains continue to change, albeit to a lesser extent than in childhood, throughout our lives.

For example, when we learn a new skill, like how to play the piano, our neural networks grow and become denser in certain parts of the brain. This is called neurogenesis. However, if we then stop playing the piano, a few months later neural pruning will take place and we will lose those new neural connections, giving some truth to the saying ‘Use it or lose it.’

Focus on research – neuroplasticity and neural pruning – Draganski et al. (2006)

Draganski et al. (2004) conducted a field experiment to determine whether, after learning a new motor skill, there would be both structural and functional changes in the brain. The researchers used MRI scans to determine if changes occurred in the brains of people learning to juggle over a span of three months. The participants were randomly allocated to two groups (juggling and non-juggling/control) and had their brains scanned three times: before learning to juggle, after three months of learning to juggle, and three months after they had ceased juggling. These scans were compared to a control group of non-jugglers.

Whilst there was no difference in brain structure between the two groups shown in the first scan, the second scan, at three months, showed that the group of jugglers had two areas of the brain that were significantly different in size from that of the control group. This difference became smaller after three months of no juggling, at the third scan.

The conclusion was that the action of watching balls in the air and learning to move in response to them strengthened the neuronal connections in the parts of the brain responsible for this activity. However, the differences were temporary and relied on continuing the activity or else neural pruning took place when the connections were no longer used. Although this was a field experiment, as the juggling practice took place under natural conditions, there was random allocation to groups and standardization of measurement, so this was a well - controlled experiment that would have high internal validity.

Neurons in certain brain areas are specific in which neurotransmitters they release and receive. This means that their action can be affected by particular drugs, both medical and recreational, before their release into the synapse and also during their uptake by the receiving neuron or reuptake by the releasing neuron.

Neurotransmission

This is what neurotransmitters do. They communicate between nerve cells (neurons). There can be as many as 100 billion neurons in the human brain and they form trillions of connections between each other. Neurons carry information as electrical impulses but neurons communicate with each other by an additional chemical process involving neurotransmitters These are chemicals that are released across a gap between the neurons called the synapse and the neurotransmitter is then picked up by the receptors of another neuron.

Excitatory and inhibitory synapses

Every neuron has receptors designated for each neurotransmitter that works like a lock and key mechanism, and this is how the neurotransmitter binds to the neuron. When the neurotransmitter combines with a molecule at the receptor site it causes a voltage change at the receptor site called a postsynaptic potential (PSP). One type of PSP is excitatory and increases the probability of producing an action potential in the receiving neuron. The other type is inhibitory and decreases the probability of producing an action potential.

Whether or not a neuron fires depends on the number of excitatory PSPs it is receiving and the number of inhibitory PSPs it is receiving. PSPs do not follow the ‘all or none’ law.

Antonova et al. showed that ACh is excitatory in synapses in the medial temporal lobe and hippocampus.

Agonists and Antagonists

All neurotransmitters are natural agonists that are endogenous (produced by the body and act inside the body). They bind to synaptic receptor neurons to generate either an excitatory or inhibitory PSP, as we read above. Chemical agonists are substances that bind to synaptic receptors and increase the effect of the neurotransmitter. They do this by imitating the neurotransmitter. If you thib nk of the ‘lock and key’ mechanism, agonists oil the lock and make it easier for the neurotransmitter to have an increased effect.

Alcohol, for example, binds with dopamine receptor sites, causing dopamine neurons to fire. The firing of these neurons results in the activation of the brain's reward system - the nucleus accumbens, and a feeling of pleasure.

Antagonists are chemical substances, both naturally found in food, and medicines, and artificially manufactured. They also bind to synaptic receptors but they decrease the effect of the neurotransmitter. Therefore, if a neurotransmitter is excitatory, an antagonist will decrease its excitatory characteristics. This is like putting chewing gum in the lock so it sticks and the key is unable to turn well.

Antonova (2011) demonstrated that ACh is an agonist in the medial temporal lobe area, and also scopolamine is an antagonist for ACh and decreases its action, reducing spatial memory ability.

The table below gives a brief description of the major neurotransmitters (there are others) and the areas of the brain where they take effect. (Again, there are others).

Table 4.1 Some major neurotransmitters and their functions

Focus on Research – serotonin - Walderhaug et al. (2007)

Walderhaug et al, (2007) aimed to investigate the role of serotonin on mood regulation and impulsivity and the role of the 5-HTT gene in the brain. conducted a study on healthy participants using a technique called acute tryptophan depletion, which decreases serotonin levels in the brain. Serotonin is a hormone in the body and a neurotransmitter in the brain, but it cannot cross the blood-brain barrier. Therefore it has to be made in the brain, and tryptophan, an essential amino acid found in animal protein can cross the blood/brain barrier and is the main building block of serotonin.

A volunteer sample of 39 men and 44 women participated in a randomized, double-blind experimental study using a technique called acute tryptophan depletion, which decreases serotonin levels in the brain. Behavioural measures were taken of impulsivity and mood.

The study showed that men exhibited more impulsive behaviour as a result of the serotonin depletion but the technique did not alter their mood. Women, on the other hand, reported how their mood worsened and they also showed signs of more cautious behaviour, a response that is linked with depressive behaviour. This means that women and men appear to respond differently to neurochemical changes.

It is already known from a significant amount of research in this field that reduced serotonin transmission contributes to the functional changes in the brain associated with a major depressive disorder (MDD) and this study, therefore, reinforces such findings. Furthermore, in the female participants, it was shown that the tryptophan depletion affected a region of the SLC6A4 gene, a gene which influences the serotonin transporter (5-HTT) in the synapse.

Such findings have contributed to the development of most of today’s most popular antidepressants being designed to temporarily block the serotonin transporter so that serotonin remains in the synaptic gap for longer.

It is also known that people with MDD are frequently found to have less impulse control, and this observation was also reinforced in this study. However, this was the first study to identify sex differences in the way that men and women react to reductions in serotonin function, specifically in terms of their mood and impulsivity.

Focus on Research – acetylcholine – Martinez and Kesner (1991)

Martinez and Kesner (1991) aimed to investigate the role of the neurotransmitter acetylcholine (ACh) in spatial memory formation. They carried out an experiment on laboratory rats who were trained to run a maze.

The rats were then divided into groups as follows:

Group 1 was injected with scopolamine which blocks ACh receptor sites and therefore reduces the availability of ACh.

Group 2 was injected with physostigmine which blocks production of cholinesterase, an enzyme which cleans up ACh from the synapses. This injection increased the availability of ACh.

Group 3 was the control group and received no injections.

The investigators found that Group 1 rats (scopolamine, less ACh) made more mistakes and were slower as they ran the maze compared to Group 2 rats (physostigmine, more ACh) that ran more quickly through the maze and made fewer mistakes. So, Group 1 was slower and made more mistakes than the control group. Group 2 was faster and made fewer mistakes than the control group.

The investigators concluded that ACh is a neurotransmitter that boosts spatial memory.

Remember that Antonova (2011) conducted a similar experiment to this, but on humans, and concluded the same. If you are answering an SAQ on the influence of one neurotransmitter on behaviour, do not use an animal study. An animal study may be used as supporting evidence for a human study in an ERQ. Both Martinez and Kesner and Antonova et al. also show that scopolamine acts as an antagonist for ACh.

Ask Yourself How does Martinez and Kesner’s study show the value of animal research when investigating the brain and human behaviour?

Hormones are chemical messengers that are secreted (secrete = given out) by glands. The difference between a hormone and a neurotransmitter is that, while both are secreted inside our bodies, hormones are produced by endocrine glands and neurotransmitters are produced within neurons when triggered by an electrical impulse. Hormones enter directly into the bloodstream, while neurotransmitters are secreted at neuron synapses. However, it is important to be aware that some chemical messengers can act both as hormones and neurotransmitters. Adrenaline is an example: it is secreted as a hormone in the body by the adrenal medulla (at the centre of each adrenal gland, just above the kidneys) when we encounter a stressful situation. Its purpose is to prepare the body for a fight or flight response by increasing the heart rate. However, it is also used by adrenal-specific neurons in the brain in the control of appetite for example.

Unlike neurotransmitters, which act in a split second, a hormone may take several seconds to be stimulated, released and reach its destination. If an immediate behavioural reaction is required, neurotransmitters and the nervous system play the major role. For a slow, steady response over a period of time, we have hormones.

Testosterone is primarily secreted in the gonads (in the testes of males and the ovaries of females), although small amounts are also secreted by the adrenal glands. It is the main male sex hormone and plays a key role in the development of male reproductive tissues such as the testes and prostate as well as promoting secondary sexual characteristics such as increased muscle and bone mass and hair growth. On average, an adult human male produces about ten times more testosterone than an adult human female, although there is a wide variation in the amounts, and there may be overlaps between high testosterone-producing females and low testosterone producing males.

Studies have connected testosterone with aggression in both males and females, but Archer (1994) reviewed the research, and concluded that there was a low positive correlation between testosterone levels and aggression in males, but a much higher positive correlation between testosterone levels and measures of dominance. While hormones may influence our responses, the social and cultural contexts must not be ignored.

Ask Yourself Which sociocultural factors are likely to be involved in aggressive behaviour?

Focus on Research – testosterone – Carré et al (2016)

Carré et al. (2016 )noted that research into the link between aggression and testosterone levels has produced inconsistent results over the last few decades. In this experiment, the researchers aimed to find out whether aspects of personality would affect aggressive responses to a game. 121 healthy male participants were randomly allocated to two groups, where one group received a placebo and one group an injection of testosterone. It was a double-blind technique wherein neither the experimenters nor the participants knew which injection they had received.

All of the participants then underwent a decision-making game that was designed to assess aggression after social provocation within the game by a partner (actually the computer).

Measures of personality with regard to dominance and impulsivity traits were assessed using questionnaires. The researchers found that an increase in testosterone levels alone was not enough to provoke aggression. Only those men who had received additional testosterone and had scored high in dominance and low in impulse control exhibited higher aggression than the control group and the rest of the testosterone group who did not possess these personality characteristics.

Focus on Research – testosterone – Nave et al. (2017)

Similarly, Nave et al. (2017) investigated the effect of testosterone on cognitive reflection in males. It would seem logical that as testosterone interacts with already low impulse control and high dominance to produce aggression, maybe it also reduces cognitive reflection. Before the 243 healthy male participants randomly received either testosterone or a placebo in a single dose of gel applied to the skin, they gave a baseline saliva sample. They then went away for a few hours to give the testosterone time to stabilise in the bloodstream, returned and gave another sample to check for the level of the hormone. After this all the participants took the Cognitive Reflection Test (CRT) that tested their ability to override impulsive judgements and snap decisions with deliberate correct responses. A sample was taken during the testing and another at the end. The results showed that the participants who received testosterone had significantly lower scores on the CRT than the control group. This demonstrates a clear effect of testosterone on cognition and decision-making. It remains to be seen if the findings found in both of these experiments would be the same in females.

4.2 Pheromones and Their Effects on Behaviour

Unlike hormones, which act inside the individual body, pheromones are produced individually, but act outside the body at species level. Therefore they are sometimes referred to as ‘exogeneous hormones’. Insects and mammals possess pheromones and there is some evidence that pheromones may play a role in human behaviour, predominantly in either mating behaviour or mother-baby bonding; however, none is conclusive. A discussion of the effects of pheromones on behaviour is a useful exercise in critical thinking.

One of the newest areas of research in psychology is the field of evolutionary psychology, an area we will be revisiting later in the biological chapter, in the section on genetics and behaviour. Evolutionary explanations of behaviour argue that some of the behaviours we witness in modern life are the legacy of genetic adaptations that contributed to survival in of the species during the time of our earliest ancestors. Although this field in psychology raises a number of practical problems in assessing how far evolutionary processes affect modern behaviour, it also raises many interesting questions regarding how we act.

One behaviour that is argued to be adaptive is the choice of a suitable mate. It is important that we choose a mate whose genes are sufficiently different from our own to avoid any problems that could be created by ‘in-breeding’. This is why there is a strong feeling against marrying people to whom you are too closely related and why brother–sister marriages are illegal in most countries. Some researchers have argued that one way in which we can identify if a person is genetically distant from ourselves is through pheromones. These are chemical hormones that, despite not having a smell, are detected by the vomeronasal organ, which lies at the base of the nasal cavity, in the soft tissue and just above the roof of the mouth.

Pheromones can only act within species and in 1959 the first to be detected was in female silkworm moths who produced the pheromone bombykol to attract males. However, later research in humans suggested that our behaviour can also be influenced by pheromones being emitted from other humans. McClintock (1971) published research that showed how women living in dormitories together often develop synchronous menstrual cycles over time. This study proposed that a pheromone emitted by each woman caused the synchronisation but did not suggest what chemical structure the pheromone may have. It has been later criticised and has been difficult to replicate successfully.

MHC (major histocompatibility complex) is a group of genes that, while possibly not pheromones, can be smelt in sweat, and if attraction to those with different MHC than our own is followed by mating (a big ‘if’), this maximises the immune responses in offspring, making them stronger.

Focus on Research – putative (possible) human pheromone – Wedekind et al. (1995)

Wedekind et al. (1995) conducted a study to investigate whether females prefer male odours from males with a different MHC from their own. This could suggest an influence of pheromones on human adults. In this study, 44 male students were asked to wear the same T-shirt during two consecutive nights. The T-shirt was kept in a plastic bag between the two nights and the men were asked to remain as odour-neutral as possible by avoiding sexual activity, smoking and the use of strongly perfumed products and foods that produced strong odours. The mean age of all participants was 25 years old and prior to the study, all male and female participants had been classified in terms of their immune system similarity via a specialised blood test.

The day after the men had worn their T-shirt for the second night, 49 female students were each asked to rate six T-shirts for pleasantness and odour intensity. three of them had been worn by males with a similar MHC to them and the other three by males with a very different MHC from them. The females had to smell the T-shirts by via a triangular hole cut into a cardboard box in which the T-shirt had been placed. Each T-shirt was assessed by the females according to how intense and how pleasant they found their smell.

The researchers found that a woman whose MHC was different from the male’s MHC found his body odour to be more pleasant than women with a similar MHC to the male’s. This finding, however, was opposite if the woman was taking the oral contraceptive pill: these women were more attracted to males who had a similar MHC to their own. Women are normally attracted to males with a different MHC than their own, but the contraceptive pill may interfere with natural mate choice based on MHC dissimilarity. Because the women who were on the contraceptive pill preferred men with similar MHC to their own, as would be found in men with a family connection to them, for example, Wedekind et al. speculated that this reflected a hormonally-induced shift owing to the pregnancymimicking effect of the pill, leading to increased association with kin who could assist in childcare.

Roberts et al. (2008) followed up on Wedekind’s findings and tested directly whether taking a contraceptive pill altered odour preferences. The procedure for the male participants mirrored that of Wedekind et al. and all participants undertook blood tests to assess immune system similarity. This study, however, used a longitudinal design with the females being divided into two groups. The first group of women were tested before and after using the contraceptive pill, whilst the second group of women formed a control group (no contraceptive pill use) but attended the testing sessions in comparable intervals to the contraceptive use group.

The findings supported those of Wedekind et al. in that there was a significant preference shift towards MHC similarity between males and females associated with pill use, which was not evident in the control group. Both Wedekind et al. and Roberts et al. concluded that contraceptive use may be interfering with natural biological mating mechanisms if dissimilarity of MHC (which is possibly a pheromone) between mates plays a role in maintaining attraction between partners within a relationship.

Focus on Research – argument against human pheromones – Doty (2010)

Despite the evidence outlined above, other researchers have disputed completely the idea that humans emit pheromones that can be detectable by other humans. One of these researchers is Richard Doty who, in his book The Great Pheromone Myth, discussed his arguments against the existence of human pheromones. Doty (2010) states that one major problem in this area of research is that no current scientific definition exists about what a mammalian pheromone actually is. Although many scientists have claimed that pheromones play an integral part in not only human mate selection but also other behaviours such as emotion and mood, Doty raises the point that human pheromones have not been chemically isolated.

He also speculates on the dangers of using research on insects that has shown evidence of pheromone action and using these findings to assume that such pheromonal processes must also exist in humans. In addition, Doty objects to the idea that one chemical can influence behavioural changes in other members of the same species given that there are multiple chemicals in the environment influencing behaviour at any one time.

Riley (2016) analysed the claims for the existence of human pheromones and, like Doty, also believes that they do not exist. Riley further states that the human vomeronasal organ has no nerve links to the brain and is therefore unlikely to influence our behaviour.

Ask Yourself What challenges do you think researchers face in trying to isolate possible human pheromones?

Genetic information is contained in chromosomes and each human has 23 pairs of chromosomes (tightly-wound strands of DNA) in each of their cells and one of each of these pairs is from each parent. Our DNA, therefore, forms a blueprint for the structure and functions of our body. The term genome is used to signify all the genes an individual possesses. Genes contain biological instructions to form protein molecules from amino acids. Proteins are essential to life because they are the building blocks of our brain and body. It is no surprise therefore that psychologists have taken an interest in how genetics may affect behaviour. The development of new techniques as a result of advances in scientific technology has meant that this area of psychology research has been able to advance in recent years.

Research has indicated that the genes in our DNA are not all active at the same time and can be ‘silenced’ or ‘de-silenced’, i.e., switched on or off. This process is called gene regulation and leads to differences in gene expression. In other words, processes within cells regulate which genes are expressed or active. To switch a gene off, and therefore prevent it from making the protein it was designed to produce, cells can use chemicals in the body called methyl groups and initiate a process called methylation to block a gene’s effects. However, a gene can be switched back on by the reverse process of demethylation. The study of how genes are switched on and off is called epigenetics. It is important to note that the genes are not permanently altered but their ability to influence our biology is manipulated: the genes will work normally again once switched back on. During development in children, however, if certain proteins are no longer needed the methylation process will be permanent. Gene expression, therefore, plays an extensive role in the developing brain.

Research has also shown that negative events during childhood can influence gene expression, as shown in the Suderman et al. (2014) study.

Focus on Research – epigenetics – Suderman et al. (2014)

Research by Suderman et al. (2014) demonstrated that 12 adults who had suffered childhood abuse were more likely to show methylation in their DNA compared to a control group of 28 who had suffered no such abuse. The participants were 45 year-old males and their blood DNA was analysed.

In particular, the study showed that there was increased methylation of the gene PM20D1 in the sample who had suffered abuse. This gene is responsible for the metabolism of amino acids and is associated with control over eating habits. Those with childhood abuse were also shown to have long-term associations with negative health outcomes, specifically, a greater prevalence of obesity among those who reported physical abuse in childhood. This supported previous research that links this gene with childhood abuse and increased obesity as an adult. This finding, therefore, shows how an environmental trigger like abuse can contribute to switching off a gene which contributes in some way to a person’s food intake. Evidence from this study indicates that there is a correlation or relationship between the methylation of gene PM20D1, child abuse, and eating habits in adults. This suggests that the interaction between genes and environmental influences can predispose a person to behave in a certain way.

Suderman et al.’s epigenetic study provides evidence for how gene expression can be affected by traumatic environmental events. Other studies with animals have also found similar results as shown in the study by Weaver et al. (2004, also referenced in some texts as Meaney et al., 2004) which investigated maternal behaviour in rats.

Focus on Research epigenetics - Weaver et al. (2004)

Weaver et al. (2004) investigated stress responses of rat pups (babies) who had received vigorous licking and grooming from their mothers in the first ten days after birth and compared them to rats who had not received much attention from their mothers. The stress response was measured by placing each rat into a small tube for twenty minutes and measuring their reaction to this confined situation. The stress hormone corticosterone (a glucocorticoid) was measured in each rat.

It was found that the rats who had more attention from their mothers had lower levels of corticosterone than the rats who had not. It could be argued that the reason these differences emerged was that the rats inherited their temperament from their mothers: the calmer rats may have had calmer mothers who as a result of being calmer in temperament were able to engage in high attention maternal behaviour with their offspring. To test this possibility the researchers carried out another study in which the offspring of anxious rats were placed with calmer mothers who frequently licked their pups, and the offspring of calmer rats were placed with more anxious mothers who did not engage in high levels of maternal licking. It was found that the reactivity to stress depended on adoptive mother behaviour and not biological mother behaviour.

This is an example of epigenetics and is explained by gene expression . The researchers showed that the glucocorticoid receptor genes in the brain are methylated (switched off) when mothers neglect their pups and these pups went on to become worse mothers. Rat pups raised by nurturing mothers were less sensitive to stress as adults. Acquired epigenetic modifications can be inherited and passed on to offspring; this is not just learned behaviour.

We can conclude from this section therefore that although we are the product of the genetic information received from our parents research has highlighted how far the environment can have an impact on genes through the process of gene expression.

Ask Yourself Why would it be impossible to conduct Weaver et al.’s animal study with humans?

Genetic similarity is referred to as relatedness. The greater the genetic similarities between two individuals or a group of individuals the higher the degree of relatedness.

(Source: IB Psychology Guide )

Twin studies

An awareness of the degree of relatedness between MZ and DZ twins, siblings, parents and children and parents and adopted children provides a critical perspective in evaluating twin or kinship studies.

As described above, psychologists have more recently been able to gain insights into how gene expression plays a role in behaviour, but a long-standing traditional technique that is still widely used today is to study how behaviour varies according to the degree of genetic similarity between relatives. This is called relatedness. As genes cannot ethically be manipulated in humans to see the effect on behaviour, family-based studies are an ideal way to assess how genes influence behaviour. Such studies are therefore correlational in nature.

As mentioned earlier, in Section 2.1, any correlational studies into the relationship between genes and behaviour measure the concordance rate of a personality characteristic or a behaviour between individuals. This means that they look at the extent to which the pairs of individuals (usually twins, both identical/monozygotic and non-identical/dyzygotic) share a behaviour. A concordance rate of 1 for a behaviour is 100% concordance, which in real life is impossible to achieve. It would mean that one twin behaved exactly the same as or had exactly the same intelligence or attitude as the other. Concordance rates of 0.7 (70%) are considered extremely high. A zero concordance rate means that there is no correlation at all between two people’s behaviour. Twin studies can be carried out in two ways: they can assess twins who have been reared together or they can study twins who have been separated and raised in different environments. The latter strategy is the most desirable in terms of research because if there is a concordance rate for certain behaviours between the twins that is higher than the rate in siblings (brothers and sisters) who are not twins, this suggests a genetic influence as they are being raised in different environments. However, the strategy of testing twins reared apart is extremely difficult to implement in reality because twins are so rare and twins raised separately are even rarer.

You will explore correlational studies as part of the biological explanations for mental disorder when you study Abnormal Psychology.

Focus on Research – correlational (twin) study – McGue et al. (2000)

McGue et al. (2000) investigated the genetic and environmental influences on adolescent addiction to tobacco and marijuana. They interviewed 626 pairs of male and female twins born in the same year. Males: 188 identical (monozygotic, MZ) and 101 non-identical (dizygotic, DZ). Females: 223 MZ and 114 DZ. They were interviewed about their history and experience of legal (tobacco) and illegal (marijuana) drug use, details of their home life; and they also completed a questionnaire.

The researchers found a slight heritability for marijuana use of 10% -25%, with no significant differences between males or females. But tobacco use showed a heritability of 40%-60%. However, the importance of shared environment was also a prominent finding: the participants with a well-established habit and history of drug-taking (both legal and illegal) reported that such drugs were a regular part of family life, with reports of parents or family members openly taking drugs, and drugs being a normal part of the home environment.

They concluded that the environment appeared to be more influential in determining drug use than genetic inheritance.

Focus on Research – correlational (twin) study – Kendler et al. (2006)

Kendler at al. (2006) conducted a very large Swedish twin study with 15,493 complete twin pairs listed in the national twin registry. The researchers used telephone interviews over a period of 4 years to diagnose major depressive disorder (MDD) on the basis of (a) the presence of most of the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders) symptoms or (b) having had a prescription for antidepressants.

The researchers found an average concordance rate for MDD across all twins was 38%, in line with previous research. They also found no correlation between the number of years that the twins had lived together and lifetime major depression, suggesting this was a true heritability rate. The rate among female monozygotic twins was 44% and amongst males 31%, compared with 16% and 11% for female and male dizygotic twins respectively. If the disorder was purely genetic, we might expect the monozygotic concordance rates to be much higher. But the difference between monozygotic and dizygotic concordance rates is enough to indicate a strong genetic component.

The difference in concordance rates between female and male twin pairs is interesting. The findings suggest that the heritability of MDD is higher in women than in men and that some genetic risk factors for MDD are sex-specific.

Limitations of twin studies

Studies into twins raised apart have weaknesses that must be taken into account when interpreting their results. Joseph (2002) argues that the main problem with studies of raised apart identical twins is that the investigators mistakenly compare reared-apart identical twins with raised-together identical twins, forgetting that both sets share several important similarities, which include common age, common sex, similar appearance and a common prenatal environment. Therefore, they are bound to have many similarities in behaviour. Joseph (2002) points out that the better comparison group would be with pairs of unrelated people of the same generation. Similarly, as McGue et al.’s study shows, it is difficult to disentangle environmental and genetic factors when testing twins who live together with their families.

Kinship (Family) studies

Family studies (the IB also calls them ‘kinship’ studies) investigate genetic heritability of a behaviour by looking at the incidence of a behaviour over a number of generations and controlling for other variables, such as environment. Usually, this is limited to three generations in most populations.

Focus on Research – correlational kinship (family) study – Fernandez-Pujals et al. (2015)

Fernandez-Pujals et al. (2015) conducted a large family study into the heritability of MDD. Around 126,000 individuals were asked to participate from the large Generation Scotland: Scottish Family Health Study (GS:SFHS). Each was asked to recommend one relative to the study. Participants were informed that the purpose of the study was to study the health of the Scottish population. From those invited and their relatives, 20,198 volunteered and were screened by clinical interview for symptoms of MDD. A final 2,706 were diagnosed as suffering or having suffered one or more episodes of MDD.

Correlations were calculated between relatives and the unadjusted heritability was found to be 44%. Once adjusted for same environment (i.e. taking into account all relatives who lived together and therefore for whom environmental factors could be relevant) the heritability of MDD was 28%. This is lower than for identical twins, which is to be expected, as these relatives shared 50% or lower of their genes, not the nearly 100% that MZ twins share. The heritability of recurrent MDD was significantly larger than that for single MDD and heritability for females was higher than that for males, but not significantly higher.

This evidence certainly suggests a genetic component in MDD.

Ask Yourself What are some of the difficulties involved in conducting twin and kinship research?

Evolution is the process by which plants and animals developed by descent, with modification, from earlier existing forms. These changes happen at the genetic level as organisms’ genes change and combine in different ways through reproduction and are passed down the generations.

Darwin’s evolutionary theory is based on the principle of natural selection. This means that the variations possessed by members of the same species have different values when it comes to survival. Those variations that are ‘adaptive’ will be the ones that allow those possessing them to survive and therefore will be passed on to future generations. If the environment stays the same the adaptive traits will remain in the gene pool, but if the environment changes, previous adaptive traits become less adaptive.

A well-known example is the long necks of giraffes which evolved to allow them to feed on the tops of trees and thus avoid starvation when other animals were feeding lower down. Giraffes without this adaptation died out. These useful adaptations are inherited and eventually, over a very long period of time, give rise to new species. Evolutionary psychologists working within the biological approach believe that many different human behaviours can be explained as being useful adaptations. We discuss evolutionary explanations for behaviour further on in this section.

Not all psychologists who believe in heritability (that our personality and behaviour are at least partly inherited from our parents) are evolutionary psychologists. Many twin and adoption studies have been carried out, exploring the relationship between heritability and intelligence, for example, but not all of these psychologists claim that intelligence is an adaptation that has proved useful through natural selection.

Evolutionary psychologists believe that if behaviour exists in society today, then it must be a useful adaptation that has helped us survive and reproduce, a concept known in evolutionary theory as ‘the survival of the fittest’. They also point out that despite the wide diversity of human beings in different cultures scattered all over our planet, there are some reactions that seem to be almost universal. Examples of these are the response of disgust to the smell of rotten eggs; ideas of what is attractive in a mate; fear or dislike of spiders and snakes. This is, they argue because such responses are adaptive.

Evolutionary psychologists are a long way from being able to prove a cause and effect relationship between our genetic inheritance and such responses, but they have generated some interesting ideas.

In addition, some evolutionary psychologists have argued that some phobias could have an evolutionary basis. One of the first researchers to put forward the idea that humans may have an innate tendency to fear certain animals, for example, was Martin Seligman in the early 1970s. This speculation was enshrined in his ‘preparedness’ theory (Seligman, 1971) in which he suggested that we are biologically ‘prepared’ to fear particular creatures for evolutionary reasons. In other words, fears and phobias of animals are adaptive for humans because they promote the survival of the species in some way. This idea makes more sense when we consider the environments that our ancestors needed to survive in. It is important to realise that many humans today live in some comfort compared to our ancestors. For example, we have more comfortable housing, we generally do not have to hunt for our food, and we have more sophisticated ways of protecting ourselves. Our ancestors, however, faced danger regularly and therefore it is possible that evolution equipped them with the necessary biological mechanisms to ensure their survival, i.e., innate tendencies to fear things such as strange animals, heights, deep water, etc.

The essence of Seligman’s preparedness theory, therefore, is that humans today are still influenced by their evolutionary origins and hence are more biologically prepared to be fearful of certain things. Another evolutionary mechanism that may have evolved to increase chances of survival could be the sense of disgust when we view certain stimuli. The wide-ranging study by Curtis et al. (2004) set out to test this possibility.

Focus on Research – evolutionary adaptation of disgust – Curtis et al. (2004)

Curtis et al. (2004) added a survey to the BBC Science website after a documentary had been shown about instinctive human behaviour on one of the BBC channels. A sample of over 40,000 people completed the survey. The majority of participants came from Europe but a small proportion of the sample came from the Americas, Asia, Oceania and Africa. The participants, 75% of whom were aged between 17 and 45 years old, viewed twenty photographs and rated them for the level of disgust on a Likert scale of 1-5.

The results indicated that photographs with objects representing a threat of disease were rated as more disgusting. A final question on the survey asked participants to choose with whom they would least like to share a toothbrush. Least acceptable was the postman (59.3%), followed by the boss at work (24.7%), the weatherman (8.9%), a sibling (3.3%), a best friend (1.9%) and the spouse/partner (1.8%). Sharing a person’s bodily fluid becomes more disgusting when the person is less familiar because there is viewed to be more of a disease threat from a stranger.

Curtis et al. suggested these results were evidence that disgust is an evolutionary mechanism for detecting disease thus plays a role in survival.

Earlier, we considered Wedekind et al.’s research on pheromones and how pheromones could be an adaptive evolutionary mechanism involved in mate choice. Although it was argued that the existence of pheromones in humans has been the subject of debate, other research has indicated that mate choice can be influenced by evolutionary processes like sexual selection, the process that favours individuals possessing features that make them attractive to members of the opposite sex or help them compete with members of the same sex for access to mates.

According to evolutionary theory, differences in terms of sexual selection should be expected in males and females of species (including humans) with internal fertilization. This is because if a female is unfaithful to her male partner, the male risks lowered paternity probability and runs the risk that his female mate is investing energy and resources mothering the child of a rival that does not contain his genes. Females of course don’t risk lowered maternity probability if their partner cheats on them, but they do risk losing their mate’s commitment and his resources to a rival female if he becomes emotionally committed to her.

Focus on Research – sexual selection – Buss et al. (1992)

Buss et al. (1992) investigated differences between men and women in terms of sexual selection. They asked participants (an opportunity sample of 202 undergraduate students) to vividly imagine scenarios involving either sexual or emotional infidelity by their partner. Participants’ distress while imagining these scenarios was assessed by monitoring various indices of emotional (e.g., questionnaire) and physiological arousal (e.g., sweat response).

The results showed that sexual infidelity generated the most distress in males, whereas emotional infidelity elicited the most distress in females. This difference corresponds with what evolutionary psychology would predict.

Buss et al. concluded that men are concerned that their sperm will be replaced by another man’s thus reducing the chances that genes will be passed on. They suffer from paternity uncertainty: they can’t be sure a baby is theirs if their female partner is unfaithful. A woman always knows a baby is hers but is concerned if her male partner becomes emotionally entangled with another woman, as this increases the likelihood that her mate will redistribute his resources and she and her baby may suffer.

This study, therefore, illustrates differences between male and females in terms of sexual selection in line with what would be predicted in evolutionary theory.

Limitations of evolutionary psychology

Evolutionary psychology has been accused of biological reductionism, reducing everything to a genetic level and ignoring human free will and the complexity of human behaviour. Evolutionary psychologists have responded to this by saying that it is the popularisation of their theory, rather than the theory itself, that has led to these criticisms. Just because they are trying to trace human behaviour back to its functional origins does not mean they do not acknowledge its complexity.

In addition, it is important to be cautious about interpreting the results of research in this area because male and female differences in sexual selection strategies for example are quite simplistic. How can they explain mate choice by females who never want children? Furthermore, the lack of archaeological evidence for how our ancestors lived their daily lives means that ancestral behaviour has to be viewed in the context of modern behaviour. Moreover, naturally we cannot know for certain what modifications over evolutionary time have been made to our genetic makeup and therefore the evolutionary approach to explaining behaviour has many difficulties in terms of its methodology.

In this chapter, animal research has been included in a number of sections in order to illustrate to some extent how far such research is fundamental to investigating the biological foundation of human behaviour. Given that some psychologists studying within the biological approach view the human as just another type of animal, sharing a similar, and similarly inherited, biological makeup, human behaviour can be understood by conducting studies on non-human animals and generalizing the results to humans. Charles Darwin also argued that the physiological makeup of different species was similar enough to warrant animals and humans being considered as comparable with each other.

Mammals such as rats, mice and non-human primates are particularly useful in psychology research because humans are also mammals hence our anatomy and physiology are comparable to these animals. For example, monkeys’ and apes’ brain activity can give an insight into human brain activity and behaviour given the similarities in structure and function. The different areas of animals’ brains are presumed to have the same function as human brains, and neurotransmitters in animals’ brains are presumed to have the same action in human brains. Rat behaviour is particularly complex and rats are strikingly similar to humans in their anatomy, physiology and genetics. With regard to mice, mice and humans share around 97.5% of their DNA. In addition, they have a short generation time and an accelerated lifespan. One mouse year, for example, equals about thirty human years. This is one reason why rats and mice are used in much animal research because effects can be observed at an accelerated rate in comparison to humans.

In clinical psychology and psychiatry, animal research has also played a major role in developing modern treatments for mental illness such as medication for illnesses like schizophrenia and depression. Using humans as the initial receivers of drugs in development would not be ethical because of the potential for physical and psychological harm, hence refining psychiatric medication on animals is seen as the only viable way of ensuring these drugs are as safe as possible. It can be seen therefore that within the fields of clinical psychology and medicine, animal-based studies have been instrumental in helping countless patients live better lives.

6.2 The value of animal models in research into the brain and human behaviour

Although the advent of sophisticated neuroimaging technology has revolutionised the study of the brain in both human and animal participants, the fact remains that this technology still cannot provide a detailed enough assessment of brain structure and physiology in comparison with invasive techniques used in animal brain research. These invasive techniques include surgical ablation and lesioning. Such procedures, as mentioned earlier, involve the deliberate removal of brain tissue (ablation) or the deliberate destruction of tissue (lesioning). The idea is that surgery of this type can be used to ascertain which brain structures are involved in different types of behaviour. The benefit of these invasive measures is that the brain can be studied in much finer detail and in a more controlled way because scientists can choose the size and location of the damage. This leads to much more precise measurements of brain function.

Martinez and Kesner (1991) conducted experimental research with rats that you read about in Section 3.4 on neurotransmitters. Their findings that acetylcholine (ACh) acted in the hippocampus and surrounding medial temporal lobe area and was important for spatial memory led to later research in humans. Antonova et al. (2011) carried out a similar experiment on humans to see if ACh acted in exactly the same way in the human brain and found that it did. See their research in Section 2.3, as an example of a well-controlled experiment demonstrating cause and effect.

Some of the human research was focused on diseases characterised by a loss of memory, such as Alzheimer’s disease. It was discovered that loss of ACh activity in the medial temporal lobe and hippocampus was one of the very early signs of Alzheimer’s disease. Drugs targeting the production of ACh in the brain have been developed for the treatment of Alzheimer’s disease. Therefore, discovering how neurotransmitters act in animal brains can lead to later clinical research on humans that can improve lives.

6.3 The value of animal models in research into hormones and/or pheromones.

Psychologists who are interested in understanding the role that hormones and/or pheromones play in shaping human behaviour rely on several types of research approaches. These would include animal research where hormone levels are experimentally altered, such as injecting mice with testosterone to measure levels of aggression or dominance. Hormones work in the same way in non-human mammals as they do in humans and therefore animal experiments with well controlled variables can isolate the effect of a hormone. The hormone insulin, which is used to treat diabetes, was discovered in an animal experiment. Testosterone seems to have a protective effect against depression. We read earlier that more women than men suffer from major depressive disorder (MDD). The study below investigates this further, using rats.

Focus on research – testosterone – Albert et al. (1986)

Albert et al. (1986) investigated the effect of testosterone on aggression in male rats. They placed the rats in cages and identified the alpha males (dominant males) by their size and strength. They measured their aggression levels when there was a nonaggressive rat placed in the same cage, by measuring behaviour, such as attacking and biting.

They then divided the alpha male rats randomly into four groups to undergo four separate surgeries:

1. Castration 2. Castration followed by implanting of empty tubes 3. Castration followed by implanting of tubes with testosterone 4. A “sham” castration followed by implanting of empty tubes (They cut open the rat and sewed it back up without actually removing the testicles).

They then measured the change in aggression when non-aggressive rats were reintroduced to the cage. Those that had the operations that reduced testosterone levels (Groups 1 and 2) had a decrease in aggressiveness but those that had the operations that kept testosterone levels intact (Groups 3 and 4) didn’t have a significant change in aggression levels.

Then the rats in Group 2 had their testosterone replaced and they showed returned levels of aggressiveness similar to those in Groups 3 and 4.

Moreover, the researchers observed that when a non-aggressive male is placed in the same cage as a castrated alpha rat then he becomes the dominant rat in the cage. Also, when a rat that had the sham operation is put in a cage with a castrated rat, the sham operation rat shows higher levels of aggression. This suggests that testosterone may facilitate behaviour associated with social dominance in rats. By experimenting on rats, Albert et al. were able to manipulate levels of testosterone and conclude that levels of testosterone affect aggression and dominance.

This study is a pre-cursor to investigations into human males and the effects of testosterone on behaviour. Of course, researchers cannot castrate human males to test the hypothesis that reduced testosterone levels correlate with reduced aggression, but they can increase testosterone levels and see if that results in increased aggression or dominance. Because of socialization, aggression or dominance in humans is not usually expressed by attacking or biting, but it is nonetheless measurable through competitive games, as in Carré et al.’s research (Section 4.1) Note that Carré et al. found that it was only when testosterone interacted with already present traits of high dominance and low impulse control that it resulted in aggression. Nave et al. (Section 4.1) found that testosterone reduced cognitive reflection, which is linked to impulse control. How might this link to Albert et al.’s selection of alpha males for their experiment?

Animal and human research into the effects of testosterone on male behaviour has also shown a reduction in this hormone to be linked to depression (Carrier and Kabbaj, 2012). It is helpful to see how animal studies can lead to human studies that test the hypotheses generated.

While there is animal research into pheromones and behaviour, none of it has been successfully generalized to humans yet, so the animal models for a hormone and behaviour remain the most useful.

6.4 The value of animal models in research into genetics and behaviour

Animal research is used to generate theory for comparable research in humans and the results of animal research are also compared with findings in humans. This is an area where there is a lot of animal research using specially bred mice. Mice share many of their genes with humans and can be bred to show specific genotypes. Also, because rodents have a much shorter lifespan that humans, differences in behaviour in response to genes is much quicker to observe. The following two studies are from earlier in this chapter, and both demonstrate gene expression in relation to environment.

Weaver et al. (2004) showed that the glucocorticoid receptor genes in the brain are methylated (switched off) when mothers neglect their baby rats (pups). This study was detailed in Section 5.1. It was a controlled experiment wherein pups were taken from their caring mothers and fostered with neglectful mothers and vice-versa, in order to identify the genetic and environmental effects of the mothers’ licking and grooming. It was found that even when pups had been born to uncaring mothers, once they were with their caring foster mother, then the glucocorticoid receptor genes were de-methylated (switched on) and their stress decreased. So this genetic response is not inherited but is a response to environment. This demonstrates epigenetics - genetic changes in response to environment.

This is similar to what was found by Suderman et al. (2014), who found that 12 adults who had suffered childhood abuse were more likely to show methylation in their DNA compared to a control group of 28 who had suffered no such abuse, even at the age of 45 years old. In particular, the study showed that there was increased methylation of the gene PM20D1 in the sample who had suffered abuse. This gene is responsible for the metabolism of amino acids and is associated with control over a person’s eating habits. Those with childhood abuse were also shown to have a greater prevalence of obesity in adulthood.

Weaver et al.’s study can show a cause and effect relationship between the licking and grooming of the pups and the demethylation of the glucocorticoid receptor genes because it is a wellcontrolled experiment. However, Suderman’s is a quasi-experiment with no random allocation to groups or control of other variables, and so can only show a correlation between the abuse, the methylation of the gene and the obesity of those who had suffered abuse as a child. This is one advantage that animal studies have over research into humans. With humans, researchers often investigate naturally-occurring events that result in biological changes in the brain and alterations in behaviour. With animals, researcher will instigate such changes in order to manipulate and control variables. This of course leads to ethical considerations. Any of the animal studies from this chapter can be used to discuss the ethical considerations of animal research.

6.5 Ethical considerations in animal research

There has been considerable debate about whether animal research should be used to further our knowledge about human behaviour. Some academics have taken a more philosophical viewpoint in this debate and discussed whether the use of animals in research is akin to concepts such as racism among humans. For example, Singer (1990) uses the term speciesism to reflect this and argues that humans and animals should be seen as equal. In addition, he believes that morally humans do not have the right to put one species’ rights before another’s. Regan (1984) agrees with this view and argues that animals should never be used in research. It can also be argued that evidence of self-awareness in animals should be a consideration against using them in psychology studies. For example, adult bonobos and chimpanzees have been shown to exhibit this ability. In one study, Gallup (1970) showed that chimpanzees could recognise themselves in a mirror, a behaviour that indicates self-awareness.

Such arguments, however, have not deflected psychology as a discipline from continuing to use animal research to explore the foundations of human behaviour. To counter ethical issues arising from such research, ethical guidelines have been developed to ensure researchers adhere to practices that minimise animal suffering. As mentioned earlier in the chapter, The American Psychological Association (APA) regularly updates its guidelines for animal research. Researchers can also use a cost-benefit analysis to weigh up the pros and cons of carrying out animal research projects. Bateson (1986), for example, proposed a decision-making tool for research called Bateson’s Cube. When researchers propose a new project with animals, Bateson outlined three factors as being important in the decision-making process. These are:

the degree of suffering by an animal

the quality of the proposed study

medical benefits of the study

As written earlier, the APA and BPS have issued regularly-updated guidelines regarding animal research and in the UK, a government licence is needed to carry out animal research. The BPS has identified the ‘3 Rs’ of animal research. These are to:

Replace animals with other alternatives - such as stem-cell research or computer modelling

Reduce the number of individual animals used (and where possible use single-cell amoebae, fruit flies or nematode worms rather than mammals)

Refine procedures to minimise suffering - ensuring all animals are well looked after

Ethical considerations should also consider whether animals could be used in natural circumstances as well as, or maybe instead of, in experiments. Observations of primates in their natural habitats, and of the effects of changing environment and family disruption on the treatment of young animals may yield richer data gained more ethically than data gained from lab studies in highly artificial circumstances. Xu et al. (2015) argued that using lab rats and mice in experiments to investigate depression that occurs naturally in a social context is not realistic. Instead, they used macaque monkeys in order to describe and model a naturally-occurring depressive state amongst monkeys raised in socially-stable groups at Zhongke Feeding Centre in Suzhou, China, where they are provided with environmental conditions and surroundings approximating those found in the wild. These circumstances make the research ethical to a greater extent than laboratory conditions would.

6.6 Assessment advice

Further Reading

The Pamoja Teachers Articles Collection has a range of articles relevant to your study of the biological approach to understanding behaviour.

Albert, D. J., Walsh, M. L., Gorzalka, B. B., Siemens, Y., & Louie, H. (1986). Testosterone removal in rats results in a decrease in social aggression and a loss of social dominance. Physiology & Behavior, 36(3), 401–407.

Antonova, E., Parslow, D., Brammer, M., Simmons, A., Williams, S., Dawson, G. R., & Morris, R. (2011). Scopolamine disrupts hippocampal activity during allocentric spatial memory in humans: an fMRI study using a virtual reality analogue of the Morris Water Maze. Journal of Psychopharmacology, 25(9), 1256-1265.

Archer, J. (1994). Testosterone and aggression. Journal of Offender Rehabilitation, 21, 3–4.

Bateson, P. (1986). When to experiment on animals. New Scientist, 109, 30–32.

British Psychological Society (2020). BPS Guidelines for Psychologists Working with Animals. Accessed 7 March 2021 from https://www.bps.org.uk/news-and-policy/bps-guidelinespsychologists- working-animals

Broca, P. (1861a). Perte de la parole, ramollissement chronique et destruction partielle du lobe antérieur gauche du cerveau. Bulletin de la Société Anthropologique, 2, 235–238

Broca, P. (1861b). Remarques sur le siège de la faculté du langage articulé, suivies d'une observation d'aphémie (perte de la parole). Bulletin de la Société Anatomique, 6, 330–357.

Buss, D.M., Larsen, R.J., Westen, D. and Semmelroth, J. (1992). Sex differences in jealousy: Evolution, Physiology and Psychology. Psychological Science, 3(4), 251–255.

Carré, J.M., Geniole, S.N., Ortiz, T.L., Bird, B.M., Videto, A. and Bonin, P.L. (2017). Exogenous testosterone rapidly increases aggressive behaviour in dominant and impulsive men. Biological Psychiatry, 82(4), 234.

Carrier, N. and Kabbaj, M. (2012). Extracellular signal-regulated kinase 2 signalling in the hippocampal dentate gyrus mediates the antidepressant effects of testosterone. Biological Psychiatry, 71(7), 642–651.

Committee on Animal Research and Ethics (CARE). Guidelines for Ethical Conduct in the Care and Use of Nonhuman Animals in Research. American Psychological Association. Accessed 7 March 2021 from https://www.apa.org/science/leadership/care/guidelines

Doty, R. (2010). The Great Pheromone Myth. Baltimore, MD: Johns Hopkins University Press.

Draganski, D., Gaser, C., Busch, V., Schuierer, G., Bogdahn, U. and May, A. (2004). Newly honed juggling skills show up as a transient feature on a brain-imaging scan. Nature, 427, 311–331.

Dronkers, O., Plaisant, M., Iba-Zizen, T. and Cabanis, E.A. (2007). Paul Broca’s historic cases: high resolution MR imaging of the brains of Leborgne and Lelong. Brain, 130, 1432–1441.

Fernandez-Pujals A.M., Adams M.J., Thomson P., McKechanie A.G., Blackwood D.H.R., Smith B.H., Dominiczak A.F., (...), McIntosh A.M. (2015) Epidemiology and heritability of major depressive disorder, stratified by age of onset, sex, and illness course in generation Scotland: Scottish family health study (GS: SFHS). PLoS ONE, 10 (11) , art. no. e0142197

Gallup, G.G. (1970). Chimpanzees: Self-recognition. Science, 167 (3914), 86–87.

NIH (n.d.). Human Genome Project. Accessed 14 March 2021 from https://www.genome.gov/human-genome-project

House of Lords (2002). Select Committee on Animals in Scientfiic Procedures Volume 1 - Report. Retrieved from https://www.publications.parliament.uk/pa/ld/ldanimal.htm

Joseph, J. (2002). Twin studies in psychiatry and psychology: Science or pseudoscience? Psychiatric Quarterly, 73(1), 71–82.

Kendler, K. S., Gatz, M., Gardner, C. O. & Pedersen, N. L. (2006). A Swedish national twin study of lifetime major depression. American Journal of Psychiatry, 163, 109–114

Lashley, K.S. (1930). Basic Neural Mechanisms in Behavior. Psychology Review, 37, pp. 1–24.

Maguire, E.A., Gadian, D.G., Johnsrude, I.S., Good, C.D., Ashburner, J., Frackowiak, R.S. and Frith, C.D. (2000). Navigation-related structural changes in the hippocampi of taxi drivers. Proceedings of the National Academy of Science, USA, 97, 4398–4403.

Martinez, J.L.J. and Kesner, R.P. (1991). Pharmacology and biochemistry: Memory: drugs and hormones. In J.L.J. Martinez and R.P. Kesner (Eds.), Learning and memory: A biological view (pp. 127–163). Orlando, FL: Academic.

McClintock, M.M. (1971). Menstrual synchrony and suppression. Nature, 229, 244–245.

McGue, M., Elkins, I., & Iacono, W. G. (2000). Genetic and environmental influences on adolescent substance use and abuse. American Journal of Medical Genetics Part A, 96(5), pp. 671- 677

Nave, G., Nadler, A., Zava, D., & Camerer, C. (2017). Single-Dose Testosterone Administration Impairs Cognitive Reflection in Men. Psychological Science, 28(10), 1398–1407.

Regan, T. (1984). The Case for Animal Rights. New York, NY: Routledge.

Riley, A. (2016). Pheromones are probably not why people find you attractive. Retrieved from http://www.bbc.com/future/story/20160509-the-tantalising-truth-about-sex-pheromones

Roberts, S.C., Gosling, L.M., Carter, V. and Petrie, M. (2008). MHC-correlated odour preferences in humans and the use of oral contraceptives. Proceedings of the Royal Society B, 275(1652), 2715–2722.

Seligman, M.E.P. (1971). Phobias and preparedness. Behaviour Therapy, 2(3), 307–320.

Singer, P. (1990). Animal Liberation. New York, NY: Avon Books.

Squire, L.R. (2009). The legacy of patient H.M. for neuroscience. Neuron, 61(1), 6–9.

Suderman, M., Borghol, N., Pappas, J.J., Pinto Pereira, S.M., Pembrey, M., Hertzman, C., Power, C. and Szyf, M. (2014). Childhood abuse is associated with methylation of multiple loci in adult DNA. BMC Medical Genomics, 7(13), 1–12.

Tierney, M.C., Varga, M., Hosey, L., Grafman, J. and Braun, A. (2001). PET evaluation of bilingual language compensation following early childhood brain damage. Neuropsychologia, 39(2), 114– 121.

Walderhaug, E., Magnusson, A., Neumeister, A., Lappalainen, J., Lunde, H., Refsum, H. and Landrø, N.I. (2007). Interactive effects of sex and 5-HTTLPR on mood and impulsivity during tryptophan depletion in healthy people. Biological Psychiatry, 62(6), 593–599.

Weaver, I.C.G., Cervoni, N., Champagne, F.A., D’Alessio, A.C., Sharma, S., Seckl, J.R., Dymov, S., Szyf, M. and Meaney, M.J. (2004). Epigenetic programming by maternal behaviour. Nature Neuroscience, 7(8), 847–854.

Wedekind, C., Seebeck, T., Bettens, F. and Paepke, A.J. (1995). MHC-dependent mate preferences in humans. Proceedings of the Royal Society Biological Sciences, 260, 245–249.

Wyatt, T.D. (2015). The search for human pheromones: the lost decades and the necessity of returning to first principles. Proceedings of the Royal Society of Biology, Vol. 282

Wyatt, T.D.(2013). The smelly mystery of the human pheromone. TED Talk https://tinyurl.com/jwdlzsj

Xu, F., Wu, Q., Xie, L., Gong, W., Zhang, J., Zheng, P., ... & Fang, L. (2015). Macaques exhibit a naturally-occurring depression similar to humans. Scientific Reports, 5, Article 9220, pp. 1-10

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• Biological Approach

Psychology is one of the many true mysteries of the sciences of today. The fundamental question it tries to answer is about the mind and soul ( psyche) relation with our physical bodies. Are the body and mind separate? Or are they the same? Each psychological approach proposes a different answer to this philosophical question, known as the mind-body problem . 

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In this article, we're going to look at how psychology uses knowledge and methods of biology in a b iological approach to answering the fundamental questions of what determines individuals' behaviour and thinking.

• First, we will give a biological approach definition.
• After, we look at some biological approach assumptions.
• Then we will explore some biological approach examples.
• Next, we will briefly look into the biological approach to depression .
• Finally, we will examine the biological approach evaluation, including biological approach strengths and weaknesses.

Biological Approach Definition

The biological perspective proposes that biological structures determine our behaviour and thoughts. These structures include neurons, brain regions, neurotransmitters or genes. A simple definition of this is:

A biological approach in psychology involves studying human biology to understand human behaviour.

In contrast to the cognitive approach, in the biological approach, the mind is not seen as separate from the physical makeup of our bodies. There is no 'ghost in the machine; instead, the physical machine is made up of many structures, e.g. cells that work together to enable us to function.

Biopsychology is where psychology and biology overlap. The essential ideas taken from biology and applied to psychology are natural selection, localisation of brain functions, and brain chemicals as a basis of behaviour. Let's have a closer look at how these ideas impact behaviour.

Biological Approach Assumptions

In biopsychology , exploring human biology and genes throughout history and today using more advanced technology has created some assumptions that the biological approach follows. There are three main ones:

• Genes determine our behaviour.
• Brain functions are localised.
• Neurochemicals are the basis of behaviour.

One of the key assumptions of the biological approach is that traits and behaviours can be inherited from our parents. It also assumes the traits get passed down from one generation to another to ensure survival in the natural environment.

To highlight how genetics and biology can influence our actions, we will look at some examples of the biological approach that aims to explain human behaviour.

Biological Approach Examples

Here we will look into some examples of biological approaches, including genes determining behaviour, evolutionary explanations of behaviour, brain functionality, and neurochemicals and behaviour.

Biological Approach: Genes Determine Behaviour

Natural selection is the idea that biological advantages of a species (e.g., sharper beaks, bigger brains, better night vision) get passed down to future generations in an inherited biological trait and was proposed by Darwin in what is commonly known as the theory of evolution .

Good to know: In contrast to everyday language, in science, a theory is an overarching idea that has been overwhelmingly confirmed by evidence. This is as close as science gets to calling something a fact. An idea that you speculate about, however, is called a hypothesis .

A century after Darwin, advances in biotechnology have allowed us to confirm the existence of inherited physical traits, or genes, in cell DNA. Geneticists are still trying to figure out how genes influence behaviour; however, twin studies and family histories show that a lot of behaviour can be explained using the ideas of genotypes and phenotypes .

We carry a specific combination of our parents' genetic information (DNA) called the genotype . However, only the dominant traits are observable. These outwardly observable genes are called phenotypes , determined by both the genotype and the environment.

Some examples of phenotypes are hair colour, height, eye colour and even behaviour.

Knowing about genotypes and phenotypes has helped us understand why some people show certain behaviours, and some don't.

Some mental illnesses, such as schizophrenia , are thought to have a genetic component as they are often found passed on in family lines but not always.

Biological Approach: Evolutionary Explanations of Behaviour

Evolutionary adaptation means the traits passed down over many generations best help the individual survive in the natural environment.

Most adaptations of the theory of evolution address physical traits. But psychology is particularly interested in behavioural traits , meaning how people have developed over time to better adapt to their environment. This includes behaviours such as altruism, attachment and communication through facial expressions.

Attention bias; e xperiments have shown that even babies tend to pay more attention to spiders and snakes than to cars. In reality, both can be equally deadly. Why could this be a useful trait in nature?

One possible explanation for this is that, over generations, those who paid attention to and consequently learned to fear spiders and snakes survived longer and had a chance to procreate more than those who died of snake- or spider bites. This would mean that the ability to learn to fear snakes and spiders is an adaptation that evolved in humans due to the environment.

Biological Approach: Brain Functionality

Biopsychology assumes that different parts of the brain have different functions rather than the whole brain working at all times.

There are many methods for studying brain anatomy, including imaging like fMRI , PET scans , post mortems , or studying the behaviour of people with pre-existing brain damage .

Research has revealed that different areas of the brain correlate with specific functions.

One of the ways that brain localisation can be proved is through transcranial magnetic stimulation (TMS), which temporarily blocks the electrical activity of specific brain regions.

Depending on which specific brain areas are targeted, people lose speech or control of their hands for a minute or two (no permanent damage occurs). This demonstrates that specific brain regions control the brain's normal use.

Biological Approach: Neurochemicals and Behaviour

A lot of behaviour can be explained by the presence or absence of specific messenger chemicals in the brain- specifically neurotransmitters , hormones and immune system messengers .

The biological approach explains that excess dopamine levels in specific brain regions cause the positive symptoms of schizophrenia . And that lower dopamine levels in other regions contribute to the negative symptoms of schizophrenia .

Evidence of the role of neurochemicals in mental illnesses is that antipsychotics that target the abundance of neurotransmitters re-absorbed and available in the synapse have shown to be an effective treatment for reducing positive and negative symptoms of schizophrenia .

Biological Approach to Depression

Another example of a biological approach to explaining psychological theories involves the aetiology (the cause of) and treatment of depression , involving neurochemicals that influence mood and behaviour.

Research links depression to a deficit of serotonin and dopamine neurotransmitters.

The biological model would treat major depression by using drug therapy , involving prescribing and taking drugs (known as antidepressants ) to correct the imbalance of neurotransmitters.

Another practical application of advances in biopsychology is transcranial direct current stimulation (TDCS), a kind of low-voltage electrical current applied to the brain, which holds promise in alleviating symptoms of depression.

However, this approach does not consider the emotions and environmental stressors that can play a part in the development and continuation of the illness, which we will discuss more in an evaluation of the biological approach.

Biological Approach Strengths and Weaknesses

The biological perspective has several advantages over other approaches but also some disadvantages. Let's break down its evaluation.

Biological Approach Strengths

First, multiple strengths of the biological approach exist, making this approach reliable and objective compared to some other approaches. Let's have a look at some of its pros:

• Objective scientific and biological evidence can be found using technology. Continually building on scientific evidence increases this research field's reliability and validity.

For instance, electroencephalographs (EEGs, which analyse sleep/wake cycles), Functional Magnetic Resonance Imaging (fMRI) machines to highlight areas of the brain being used during specific actions and, as mentioned previously, drug therapy and genetic analysis in twin studies.

• Real-world applications of these biological discoveries help to improve people's lives greatly. As we have mentioned with drug therapy treatments, other examples include drugs (e.g. L-Dopa) that increase dopamine levels for people with Parkinson's Disease to reduce shaking and muscle spasm symptoms.

Biological Approach Weaknesses

Although there are many advantages to the biological approach, it's not perfect. Let's take a look at some of the weaknesses of this approach:

• The approach oversimplifies humans and our physiology. Other factors may influence our behaviour, and one biological treatment may not help those affected by external issues.
• Determinism relating to the biological approach is the concept of thinking if people's behaviour is determined by their genetics and biology, then can they truly control and be held accountable for this behaviour? This brings up philosophies about the human ability of free will and whether we are consciously responsible for our behaviour.
• It is said the biological approach doesn't consider individual differences within people. People may be biologically similar but not identical, so can it really be assumed that a biological treatment will work best for the majority? There can be differences in gender, ethnicity and neurodiversity that may mean biological approaches cannot be generalised to the whole population so easily.
• There are issues of correlation vs causation in scientific research. A correlation assumes that as one variable changes (e.g. neurotransmitter levels), the other variable changes (e.g. mood). The issue is that we can't establish which variable is the cause and which is the effect or understand if any mediational processes are influencing these findings.

Recently, health psychology has started applying an updated version of the biological approach to illnesses called the biopsychosocial model.

The model has more of a holistic view of psychological well-being and tries to address all the different social, psychological and biological factors that could influence people's thoughts and behaviour.

Biological Approach - Key takeaways

• The biological approach tries to explain the behaviour and thinking of individuals through biological structures.
• The core assumptions of the biological approach are that genes and neurochemicals determine behaviour. Another hypothesis is that brain functions are located in specific parts of the brain.
• The biological approach believes that depression is linked to a deficit of serotonin and dopamine neurotransmitters.
• The strengths of the biological approach are that there are many practical applications for biological research into the behaviour and that the methods used are scientifically sound.
• The weaknesses of the biological approach are that other possibly important variables aren't taken into account and that it's a correlative approach. It opens up questions in society and law regarding whether people can be held accountable if their biology determines behaviour.

Flashcards in Biological Approach 121

What is a genotype?

Genotype refers to the genetic makeup of an organism.

What is phenotype?

Phenotype refers to the result of genes interacting with the environment.

What is the difference between genotype and phenotype?

Genotype influences phenotype, but the phenotype is not the same as the genotype. Phenotype is the result of genes interacting with the environment.

What is an example of a genotype?

An example of a genotype is DNA.

What is an example of phenotype?

An example of phenotype is a person’s height.

What is an example of a genotype affecting behaviour?

MAOA is an example of a genotype affecting behaviour. Specifically, MAOA influences aggression.

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Frequently Asked Questions about Biological Approach

How does the biological approach explain human behaviour?

The three main biological assumptions of human behaviour are: 

• Genes determine our behaviour. 

What is the biological approach?

The biological perspective proposes that biological structures and their functions determine our behaviour and thoughts.

What are the strengths and weaknesses of the biological approach?

• Science-based on measurable data.
• Real-world applications.

Weaknesses:

• Oversimplification.
• Determinism.
• Individual differences are ignored.
• Correlation is not causation.

Is the biological approach reductionist?

A focus on the biological aspect of human thought and behaviour is reductionist, as other areas (such as our environment) are not considered. 

How is the biological approach used in social care?

By using biological treatments such as medications in drug therapy.

Test your knowledge with multiple choice flashcards

True or false: Behaviour results from genetics and the environment.

True or false: Caspi et al. prove a link between environment and behaviour.

Which one is not an example of biological structures determining behaviour or thinking?

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Case studies as a biological research process

1993, Design studies

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IB BioPsychology

Helpful Biology & Psychology notes for IB students

Ethical Considerations in the biological approach

In this essay, I’ll describe the ethical considerations in the biological approach studies. Research of the biological level of analysis poses various different ethical considerations, including concerns regarding the protection of harm, informed and conscious consent. I’ll describe two studies that rise different ethical questions regarding the studies: the Newcommer (1999) experiment and the HM Milner (1966) case study. 

The Newcommer (1999) study’s aim was to examine the role of stress on the verbal declarative memory: VBM. The participants were all students of the same university. Prior to the experiment they were assessed by a physician, and excluded from the sample if they had suffered a head injury, had a history of mental illness, suffered a head trauma or were pregnant. 

They were then divided into three groups. Each of the participants was to take a pill containing a set dosage of cortisol, a substance often called a ‘stress hormone’. It’s responsible for controlling thirst, hunger, need for sleep, as well as controlling the glucose levels in the bloodstream. 

The first group of participants was given pills containing 160mg of cortisol, an amount similar to these experienced when under a highly stressful life event. The second group was given pills with 40mg cortisol, which corresponds to a concentration similar to a mildly stressful event. Third group served as a control, and was given placebo pills with no cortisol. 

The participants were to listen and recall a prose paragraph. Each day of the experiment, there were given a different fragment. The paragraphs were counterbalanced to ensure the difficulty of the paragraphs wasn’t a confounding variable. The study first started with a baseline study to make sure there were no differences in memorizing capacities between participants. It should be noted down the experiment was double-blind, neither the participant, nor the researcher knew who received what treatment. 

The participant’s ability to memorize the prose paragraphs was then measured the first and fourth day of the pill treatment. 

On the first day of the experiment, the differences between groups were statistically insignificant, however on the fourth day participants who received the 160mg pills had a significantly worse VBM performance recorded, as compared to the placebo. On the other hand, cortisol given to the participants of the 40mg group might’ve assisted their memory formation.

It’s been concluded that prolonged exposure to severe stress impairs memory. The results are reasonable as there are cortisol receptors at the hippocampus- part of the brain responsible for the transfer of short-term memory to long-term memory. 

One ethical consideration that is concerning in this study is the protection from harm. It’s hard to evaluate to what extent were the participants able to comprehend the effects of receiving cortisol pills. Furthermore, participants were not under surveillance of the researcher at all times during the experiment, which poses a potential risk in their daily life activities. The additional stress the participants underwent might’ve negatively affected their mood, relationships or affect their judgement. On the other hand, after six days after finishing the procedure, participants memory was assessed again to make sure there were no long-terrm effects on the health of participants. Furthermore, the participants were properly informed about the procedure before giving a consent. Their health has also been assessed prior to the experiment, which further aligns the study with the ethical standards.

Other study that concerns the ethical issues is the case study of HM. As a 7-year-old boy, HM suffered a head trauma, as he was hit by a bicycle. He started to experience epileptic seizures when he was 10. At the age of 27 the seizures disabled his ordinary functioning, and therefore he decided to have a surgery procedure. William Scoville, a renowned neurosurgeon, removed both sides of his hippocampus as well as the medial temporal lobe. The surgery ceased HM’s seizures. His IQ slightly improved, and his personality was largely intact. However, soon after surgery it became evident HM suffered from a retrograde and anterograde amnesia. HM couldn’t remember past 12 years before the surgery, and wasn’t able to acquire new semantic and episodic knowledge. Brenda Milner, a researcher that was examining his case, found out that his procedural memory was left functioning- he still remembered how to mow a lawn, and could learn to draw a star while looking in a reflection in the mirror. The retrograde amnesia retreated with time- by 1966 HM was missing about 1 year of events before the surgery. The anterograde amnesia persisted. His memory was being assessed over the course of 50 years. Milner used method triangulation- psychometric and cognitive tests, as well as interviews with family members, HM and the observation of his behaviour. While taking a test, he could remember numbers if he would constantly repeat them to himself, but few minutes after the test, he wouldn’t even remember he’d taken one.

The Milner’s research significantly contributed to understanding of the brain functions, and helped to develop understanding about the localization of a function of the brain, as well as its compartmentalization. The hippocampus was found to be responsible for the transfer of short-term memory to long-term memory. Without it, HM was unable to create new ones. Furthermore, the medial temporal lobe as well as hippocampus are responsible for recall and organization of already created long-term memories, which explains HM’s reversable retrograde amnesia. 

Milner’s case study of HM meets high ethical standards of consent, confidentiality and protection from harm. The study was longitudinal, taking over 50 years. During that time, HM’s real name wasn’t known to the public until his death. Milner acquired consents for HM’s study from him, as well as his family. Concerning factor, however, is whether HM was really able to give a conscious consent, given his condition. Understanding the true extent and length of the research done by Milner might’ve been impossible to HM, as he wasn’t able to remember any of the studies, after they’d taken place. His brain was extensively studied for the majority of his life, which raises some concerns about the reduction of harm. Spending such an extensive time under expertise could’ve hindered HM’s abilities of focusing on personal goals. Furthermore, not all of his memory was shut. He was able to create new, procedural memories. He retrieved his amygdala, which leads to believe his emotional memory might’ve also been partially functioning. Therefore, it’s uncertain whether procedures performed on HM made him more self-conscious than he’d be normally be.  This, however, is significantly overweighted by the previously mentioned advantages of Milner’s research.

To conclude, ethical concerns in biological approach are not always objectively measurable. Although a study might meet ethical standards, it does not guarantee that all of the side effects were considered. It’s impossible for researchers to completely eliminate the risks, however it’s highly important participants are well informed and aware of the procedure of the experiment, are protected from both psychological and physical harm, their data is appropriately debriefed, and that they are not deceived. Newcommer and HM studies both make sure the consent of the participants is given, however HM study might be concerning in regards to the participant’s ability to grant it. Studies rise concerns about the protection from harm. Newcommer participants health could’ve been negatively affected as a result of a mood change and memory impairment, while HM could’ve experienced some psychological stress as a result of being aware of his situation. Newcommer study participants were also debriefed after taking the experiment. The anonymity of participants of the both of the studies was appropriately kept anonymous.

Popov, Alexey, et al.  IB Diploma Programme: Psychology Course Companion . 2nd ed., Oxford University Press, 2017. 

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Understanding Twins

Case study: identical twins reared in different cultures, cultural effects can be seen in some traits in reared-apart identical twins..

Posted June 27, 2022 | Reviewed by Kaja Perina

• Cultural effects were observed in individualism-collectivism in separated twins, raised in South Korea and the U.s.
• Reared-apart twins are valued in research--especially those raised in different cultures.

Twins raised apart are highly valued in psychological research. Studies have shown that genetic factors underlie a wide range of behaviors, including, intelligence , personality and interests. Twins raised apart in different countries are a unique subset of twins reared apart. They are also very informative for revealing the extent to which cultural factors may affect the similarity of identical twins -- therefore, it is very important to include such cases in the general and professional literature.

I have written about a number of such cases and was fortunate to discover several new cases quite recently. My latest report concerns identical South Korean female twins, one raised in South Korea (K) by her birth parents and the other raised in the United States (U) by her adoptive parents. The circumstances of their separation are extraordinary.

When and How Were The Twins Separated?

The twins were born in 1974. When they were two years old their grandmother took them to a market. Somehow, U got away, was picked up and brought to a hospital. She then entered a foster home before being transferred to a baby care facility. Her case was eventually managed by the Holt International Adoption Agency whose staff arranged for her to be adopted by a couple from the United States.

U’s biological mother and father were desperate to find her. They distributed printed information asking for help, and they also went on a television program for missing persons.

Discovery of Separation and Twinship

As part of South Korea’s program for reuniting adopted-apart family members, U sent a DNA sample to the data bank. In March of 2020, she received a telephone call that was life-changing---her biological mother had been identified in South Korea. During an online meeting several months later, U learned that she had a twin sister, as well as a biological brother four years older and a biological sister two years older.

I learned about U and S when I did an interview and discussion for a group called Boston Korean Adoptees (BAK), Inc. That session took place in October 2020.

I contacted my South Korean colleague, Dr. Yoon-Mi Hur, a faculty member at Kookmin University and Director of the Kookmin Twin Research Institute, in Seoul. She and I have collaborated in the past on similar case studies. We agreed that Dr. Hur would study S, I would study U, and then we would combine our results. Each twin completed a general ability (Wechsler IQ) test, administered by a trained assistant in their respective countries. The twins also completed an array of other protocols, such as a life history interview, self-esteem survey, family environment form, personality questionnaire, job satisfaction survey, individualism-collectivism assessment, and twin relationship questionnaire. I will focus on selected aspects of this case study. At the end of this essay I will provide a source for finding additional information.

The twins’ parents and families were very different as indicated by the family environment form. For one thing, S grew up in a more nurturing and supportive environment than U. Nevertheless, the twins showed favorable and similar levels of self-esteem, suggesting genetic effects. They also showed similar performance in personality, e.g., in the trait of conscientiousness . However. their general ability scores were quite different—U scored 84, while S scored 100. Their difference of sixteen points exceeds the mean difference of 6 points reported for identical twins reared together. This could be partly due to U’s history of concussions, which also may have affected her performance on a test of non-verbal reasoning. U also described herself as having a history of being a poor test-taker. However, the twins did show similarities in selected subtests that comprise the Wechsler test. Perhaps the most interesting outcome for me and for my collaborator concerned the twins’ score in individualism-collectivism.

Here, U’s scores show that she perceives the self as autonomous and believes that members of a collective are equal in status. This suggests that U has adapted well to American culture. S’s scores suggest that she perceives the self as a part of a collective and is willing to accept hierarchy and inequality within that collective. This is consistent with the South Korean culture of her age. In sum, the United States is largely an individualistic culture, while South Korea is mainly a collectivist culture. The twins’ scores reflect the importance of culture on their respective value systems.

The twins described here offer a look into how rearing in different environments and cultures can affect people with identical genetic endowments. Cultural climates can modify values, as shown by the individualism-collectivism assessment. It is likely that other transnational reared-apart identical twin pairs will be identified; in fact, I am working with some pairs because it is important to include them in future studies.

Segal, N.L., & Hur, Y.-M. (2022). Personality traits, mental abilities, and other individual differences: Monozygotic female twins raised apart in South Korea and the United States. Personality and Individual Differences, 194, 111643.

Nancy L. Segal, Ph.D. , is a professor of psychology and the Director of the Twin Studies Center, at California State University, Fullerton.

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• Published: 25 June 2024

Sequencing-based analysis of microbiomes

• Yishay Pinto 1 , 2 &
• Ami S. Bhatt   ORCID: orcid.org/0000-0001-8099-2975 1 , 2  

Nature Reviews Genetics ( 2024 ) Cite this article

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Microbiomes occupy a range of niches and, in addition to having diverse compositions, they have varied functional roles that have an impact on agriculture, environmental sciences, and human health and disease. The study of microbiomes has been facilitated by recent technological and analytical advances, such as cheaper and higher-throughput DNA and RNA sequencing, improved long-read sequencing and innovative computational analysis methods. These advances are providing a deeper understanding of microbiomes at the genomic, transcriptional and translational level, generating insights into their function and composition at resolutions beyond the species level.

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Acknowledgements

The authors thank B. Doyle, M. Grieshop, M. Gill and J. Shanahan for their thoughtful comments on the review. We also thank the Bhatt lab for helpful discussion throughout writing this review. The Bhatt lab is supported by National Institutes of Health R01AI148623 and R01AI143757. A.S.B. is supported by the Allen Distinguished Investigator Award. Y.P. was supported by the School of Medicine Dean’s Postdoctoral Fellowship.

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Viruses that infect bacteria and can sometimes insert their genetic material into the genome of their host cells.

Metric to quantify the dissimilarity in species composition between two different ecological or microbial communities.

Directed graphs (graphs in which the edges have a direction) used for genome assembly. Nodes in de Bruijn graphs represent short genomic sequences ( k -mers) and edges represent overlapping ends. By following the connection in the graph, short-read sequences are assembled into longer contigs.

Faith phylogenetic diversity is a within-community diversity metric that considers community richness weighted by phylogeny. Faith phylogenetic diversity uses a phylogenetic tree to incorporate the evolutionary relationships between species in a community.

Mobile genetic elements that can capture genes from other sources and then mobilize and transfer these genes to other organisms via horizontal gene transfer.

The collection of microorganisms, including bacteria, viruses, fungi and other microbes, that inhabit a particular environment or organism. Sometimes the term is used to refer to the genomes, transcriptomes, metabolomes, etc. from a community, and the term ‘microbiota’ is used to describe the collection of organisms, themselves.

All of the genes that exist within organisms of a given clade, including core genes, which are common to all of the organisms within that clade, and unique or accessory genes, which are present in one or a subset of the organisms within the clade.

A diversity metric that considers both the richness (number of species, for example) and evenness (abundance uniformity) in an ecological community.

Metric to quantify the distance between two ecological or microbial communities that uses a phylogenetic tree to incorporate evolutionary relationships between the taxa in the community. Can be either weighted by species abundance (also takes into account the taxonomic abundances) or unweighted (using only the presence or absence of the taxa).

A type of artificial neural network that can encode high-dimensional data into a lower-dimensional representation, known as a latent representation. In the context of binning, VAMB utilizes variational autoencoders to encode tetranucleotide frequencies and sequence abundance of sequences that require binning. These encoded representations are then clustered to identify bins.

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Pinto, Y., Bhatt, A.S. Sequencing-based analysis of microbiomes. Nat Rev Genet (2024). https://doi.org/10.1038/s41576-024-00746-6

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Hydrodynamics and water quality of a highly anthropized wetland: the case study of the Massaciuccoli basin (Tuscany, Italy)

• Pasquetti, Francesca
• Natali, Stefano
• Luppichini, Marco
• Bini, Monica
• Del Seppia, Nicola
• Delgado-Huertas, Antonio
• Giannecchini, Roberto

Owing to increasing anthropogenic impacts, wetlands have suffered a serious environmental decline in recent decades. The sustainable management of these natural resources is fundamental to maintain both the ecosystems and the economic activities. The Lake Massaciuccoli and nearby areas represent one of the largest residual coastal marshy areas in Tuscany (Italy). This wetland is characterized by large-scale and intensive agricultural use and affected by reclamation activities, with consequent problems of erosion, subsidence and lake eutrophication and siltation. In this context, an integrated study combining hydrochemical data (water levels, electrical conductivity, pH, turbidity, major ions, trace metals) and stable isotopes (H, O, S) has been performed in the southernmost part of the basin, to better disentangle processes and interactions between groundwater and surface water and to understand the origin of solutes and their evolution. Our results indicated that both groundwater and surface water have a meteoric origin and that geochemical composition of groundwater is mainly affected by local geological and biological processes. Moreover, surface water is affected by sea water mixing and evapotranspiration/precipitation processes. The impact of agricultural activity and the use of fertilizers on the water quality appears to be limited as regards nitrates, indicating that less intense agricultural practices implemented in recent years have been successful. As regards sulfates, Fe, and Mn, we cannot fully elucidate the mechanisms underlying human influence, but the oscillation of water level and degradation of peat enhanced by reclamation and agriculture activities likely played an important role in controlling the fate of these elements. Overall, these results underline the importance of integrated approaches to disentangle geochemical processes and will be useful in supporting policy implementation and environmental protection in this valuable area of Tuscany. Findings from this work suggest the need for policy-making authorities to take actions as soon as possible to mitigate risks. Closer co-operation is essential between authorities and farmers to reduce inputs of fertilizers and chemicals into the lake and the surrounding area. Also, additional policy measures should be enforced to reduce the mechanical soil tillage and limit erosion and runoff, such as the NBSs implemented within the Phusicos Project.

• Massaciuccoli;
• Human pressure;
• Hydrochemistry;
• Stable isotopes;
• Multivariate statistics;