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.

1. The Rise of the Biological Approach in Psychology

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.

2. Research Methods of the Biological Approach

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.

2.2 Case Studies

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.

2.3 Experiments

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.

2.4 Ethics and Research Methods of the Biological Approach

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.

3. The Brain and Behaviour

3.1 Techniques used to Study the Brain in Relation to Behaviour

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

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 scans

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.

Study

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

PET scans

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.

3.2 Localisation

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.

Figure 4.1 The major areas of the brain

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.

Study

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?

3.3 Neuroplasticity

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.

3.4 Neurotransmitters and Their Effect on Behaviour

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.

Figure 4.2 Diagram of a 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.

Study

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

Figure 4.3 Diagram of a synapse

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.

Study

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).

Neurotransmitter	Function	Excitatory/ inhibitory	Agonist/ Antagonist
Acetylcholine (ACh)	Responsible for stimulation of muscles, for some memory functions, and has a role in sleep. There is a link between ACh and Alzheimer’s disease: there can be up to a 90% loss of ACh in the brains of people suffering from this disease.	Usually excitatory	Scopolamine = antagonist
Dopamine	Strongly associated with reward mechanisms in the brain. Drugs like cocaine, opium, heroin and alcohol increase the levels of dopamine, as does nicotine. If it feels good, dopamine neurons are probably involved! Low dopamine levels are associated with Parkinson’s disease, and too-high levels have been correlated with schizophrenia and social anxiety.	Usually inhibitory, but can be excitatory, depending to which receptors it binds.	Alcohol = agonist Antipsychotic drugs (Haloperidol) = antagonist
Noradrenaline	Increases heart rate and blood pressure. Plays a role in wakefulness and arousal, eating, depression and mania.	Usually excitatory	Amphetamines (‘speed’) = agonist
Serotonin	Intimately involved in emotion and mood. Too little has been shown to lead to depression, problems with anger control, obsessive-compulsive disorder and suicide. Too little also leads to an increased appetite for carbohydrates (starchy foods) and trouble sleeping, which are also associated with depression and other emotional disorders.	Usually inhibitory	Hallucinogens such as LSD, mescaline and Ecstasy = agonist

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?

3.5 Assessment Advice

Question	Study/Studies
SAQs Outline/describe/explain	Suggested studies
One research method (approach to research) used when investigating the brain and behaviour	Any one of the studies listed below are suitable for these SAQs
One ethical consideration when investigating the brain and behaviour	Any one of the studies listed below are suitable for these SAQs
One technique (or one study into one technique) used to understand the brain and behaviour	Maguire et al. (2000) or Antonova et al. (2011)
Localization (or one study into localization) of function and behaviour	Maguire et al. (2000) or Antonova et al. (2011)
Neuroplasticity (or one study into neuroplasticity) and behaviour	Maguire et al. (2000) or Draganski et al. (2006)
Neural networks (or one study into neural networks)	Maguire et al. (2000) or Draganski et al. (2006)
Neural pruning (or one study into neural pruning)	Draganski et al. (2006)
One neurotransmitter and its effect on behaviour	Antonova et al. (2011) or Walderhaug (2007)
How one excitatory or inhibitory neurotransmitter (synapse) affects behaviour	Antonova et al. (2011)
One agonist and its effect on one behaviour	Antonova et al. (2011) (ACh)
One antagonist and its effect on behaviour	Antonova et al. (2011) (scopolamine)
ERQs Discuss/evaluate/contrast/to what extent?
Research methods (approaches to research) used when investigating the relationship between the brain and behaviour.	Any two of the studies listed below are suitable for these ERQs. (Ensure for a methods question, that each study uses a different methods).
Ethical considerations of research investigating the relationship between the brain and behaviour.	Any two of the studies listed below are suitable for these ERQs. (Ensure for a methods question, that each study uses a different methods).
ERQs Discuss/evaluate/contrast/to what extent?
Studies (research) investigating the relationship between the brain and behaviour.	Maguire et al. (2000) and Draganski et al. (2006)
Techniques used to study the brain in relation to behaviour	Maguire et al. (2000) and Antonova et al. (2011)
Localization (or studies into localization) of function and behaviour	Maguire et al. (2000) and Antonova et al. (2011)
Neuroplasticity (or studies into neuroplasticity) and behaviour	Maguire et al. (2000) and Draganski et al. (2006)
The influence of one or more neurotransmitters (or studies into the influence of one or more neurotransmitters) on behaviour	Antonova et al. (2011) and Martinez and Kesner (1991) or Walderhaug (2007)

4. Hormones, Pheromones and Behaviour

4.1 Hormones and Their Effect on 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.

Figure 4.6 The endocrine system

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?

4.3 Assessment Advice

Question	Study/Studies
SAQs Outline/describe/explain	Suggested studies
One research method (approach to research) used when investigating the relationship between hormones and/or pheromones and behaviour	Any one of the studies listed below are suitable for these SAQs
One ethical consideration when investigating hormones and/or pheromones and behaviour	Any one of the studies listed below are suitable for these SAQs
One hormone (or one study into one hormone) and its effect on one behaviour	Carré et al (2016) or Nave et al. (2017)
One pheromone (or one study into one pheromone) and its effect on one behaviour	Wedekind et al. (1995)
ERQs Discuss/evaluate/contrast/to what extent?
Research methods (approaches to research) used when investigating the relationship between hormones and/or pheromones and behaviour	Any two of the studies listed below are suitable for these ERQs. (Ensure for a methods question, that each study uses a different methods).
Ethical considerations of research investigating the relationship between hormones and/or pheromones and behaviour	Any two of the studies listed below are suitable for these ERQs. (Ensure for a methods question, that each study uses a different methods).
The relationship between one or more hormones and behaviour (or research/studies into the relationship between one or more hormones and behaviour)	Carré et al (2016) and Nave et al. (2017) or Albert (1986) (See HL extension, animal research)
The relationship between one or more pheromones and behaviour (or research/studies into the relationship between one or more pheromones and behaviour)	Wedekind et al. (1995) and Doty (2010)

5. Genetics and Behaviour

5.1 Genes and Behaviour

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?

5.2 Genetic Similarities

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.

(Source: IB Psychology Guide)

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?

5.3 Evolutionary Explanations for Behaviour

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.

5.4 Assessment Advice

Question	Study/Studies
SAQs Outline/describe/explain	Suggested studies
One research method (approach to research) used when investigating genetics and behaviour	Any one of the studies listed below are suitable for these SAQs
One ethical consideration when investigating genetics and behaviour	Any one of the studies listed below are suitable for these SAQs
One gene (or one study into one gene) and its influence on one behaviour	Suderman et al. (2014)
Genetic similarity in relation to one behaviour	Kendler et al. or Fernandez-Pujals et al. (2015)
One twin study or kinship study into one behaviour	Kendler et al. or Fernandez-Pujals et al. (2015)
One evolutionary explanation for one behaviour	Curtis (2004) or Buss et al. (1992)
ERQs Discuss/evaluate/contrast/to what extent?
Research methods (approaches to research) used when investigating the relationship between genetics and behaviour	Any two of the studies listed below are suitable for these ERQs. (Ensure for a methods question, that each study uses a different methods).
Ethical considerations of research investigating the relationship between genetics and behaviour	Any two of the studies listed below are suitable for these ERQs. (Ensure for a methods question, that each study uses a different methods).
The relationship between (or research/studies investigating the relationship between) genetics and behaviour	Suderman et al. (2014) and Weaver et al. (2004)
One or more genes (or research/studies into one or more genes) and their influence on behaviour	Suderman et al. (2014) and Weaver et al. (2004)
Genetic similarity (or research/studies into genetic similarity) in relation to behaviour	Kendler et al. (2006) and McGue et al. (2000) or Fernandez-Pujals et al. (2015)
One or more evolutionary explanations (or research into one or more evolutionary explanations) for behaviour	Curtis (2004) and Buss et al. (1992)

6. The Role of Animal Research in Understanding Human Behaviour

6.1 Can Animal Research Provide an Insight into Human Behaviour?

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.

Studies

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.

Studies

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

Figure 4.5 Bateson's cube

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

Question	Study/Studies
ERQs Discuss/evaluate/contrast/to what extent?
The value of animal models in understanding the relationship between the brain and human behaviour.	Martinez & Kesner (1991) and Antonova et al. (2011)
The value of animal models in providing insight into the influence of hormones and/or pheromones on human behaviour	Albert et al. (1986) and Carré (2016)
The value of animal models in providing insight into the influence of genetics on human behaviour	Weaver et al. (2004) and Suderman et al (2014)
Ethical considerations in animal research	Any of the animal studies from this chapter may be used
Ethical considerations in animal research investigating the brain and behaviour	Martinez & Kesner (1991)
Ethical considerations in animal research investigating hormones and/or pheromones and behaviour	Albert et al. (1986)
Ethical considerations in animal research investigating genetics and human behaviour	Weaver et al. (2004)

Further Reading

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

References

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