IB Psychology (BLOA): Patterns of Behaviour can be Inherited

The biological approach to psychological research relies on three key assumptions:

• Patterns of behaviour can be inherited, which means that we don’t only inherit our hair and eye colour from our parents and grandparents, but also our attitudes and behaviours.
• Animal research may inform our understanding of human behaviour, because many animals have brains and nervous systems that are similar to humans
• Cognitions, emotions and behaviours are products of the anatomy and physiology of our nervous and endocrine systems. In other words, the structure and processes of our brain and nervous system govern how we feel and think.

These key assumptions are the principles underpinning all psychological research carried out within the biological approach.

Key Question: Outline the key assumptions of the biological approach.

The biological approach does just what you would think from the name: it assumes that our behaviour is the product of our physiology, that it can be researched by investigating our physiology (or even animal physiology) and that behaviour patterns are also inherited from our ancestors, both recent and distant.

1. Patterns of Behaviour can be Inherited

This idea is the basis of behavioural genetics. Behavioural geneticists study the inheritance of patterns of behaviour by investigating how much of people's behaviour is determined by the genes they inherited from their parents and how much is caused by their environment, such as their education or their upbringing. In humans, this information is often gathered through the use of twin studiesor adoption studies, because identical twins share identical genes and adopted children share no genes whatsoever with their adoptive family. Therefore, twin studies provide an effective way of isolating the effect of genes and adoptive studies are useful for identifying the effect of environment on behaviour.

Key Study 1: McGuffin et al (1996)

Aim: To estimate the contribution of genes and shared family environment to the tendency to having major depressive disorder, and to examine the influence of characteristics of one twin suffering from the disorder on the likelihood of the other suffering from it.

Method: This was a study of 177 twins (“probands”) suffering from major depression between 1948 and 1986 and their same-sex co-twins. The sample was taken from a hospital register. Diagnostic assessments and more detailed interviews were carried out, and the interviewers were blind as to whether the twin was one of identical (MZ) or non-identical (DZ) twins and also had no information on the mental health of the other member of the twin pair. One of a twin pair was usually interviewed by a different researcher than was the other. Doctors’ reports from the hospital and from family doctors were also investigated. Correlations in the presence or absence of depression in the co-twin were calculated.

Results: The concordance rate of major depressive disorder for MZ twins was 46% and for non-identical (DZ) twins was 20%. Durations of depressive episodes that were less than 13 months were correlated more strongly with depression in the other twin. When the researchers compared the incidence of depression in the identical twins at aged 65 years with the expected incidence of depression in the general population at that age, they found that the heritability factor rose to 70%.

Conclusion: There is a strong genetic component to major depressive disorder, and no evidence for it being caused by a shared family environment. A shorter duration in one twin increased the likelihood of the other twin being a sufferer, suggesting that this was one criterion for a higher genetic component.

Evaluation

Strengths: One main strength of this study is its methodology. The researchers were careful to conduct a blind experiment with the researchers not knowing in advance whether they were interviewing the original twin, who had already been diagnosed with depression, or the co-twin, who may not have been. The study used data from a hospital register, details from family doctors and interviews with the people themselves. This triangulation of approach should raise the reliability of the data.

Limitations: When comparing the likelihood of having had major depressive disorder by the age of 65 between the participants in this study and the general population, figures for the general population were gathered from the surrounding London area in which the hospital was based. Yet people came from all over the UK to attend that particular hospital (the Maudsley), which was famous for its treatment of depression. National figures may therefore have been more representative. The researchers themselves admit that their general population estimates of the likelihood of major depressive disorder (8.4% for women and 3.6% for men) were much lower than the estimates of a similar study conducted in Virginia, USA, which gave the lifetime figure for women as over 30%.

Critical Thinking Points

Could the participants remember accurately? – The research took place nearly ten years after the last patient was added to the hospital register. This means that many of the interviews were retrospective where people were asked to remember back as many as ten or fifteen years or sometimes even more and give details of depressive episodes. This has to bring into question the reliability of such memories.

Are they representative of people with major depressive disorder? - The sample used was of people who had been depressed enough to have sought medical treatment at a hospital and may not be representative of the general population of people suffering depression, many of whom are treated in the community rather than hospitalised.

For More Study Notes…

To keep up-to-date with the tutor2u Psychology team, follow us on Twitter @tutor2uPsych, Facebook (AQA) / OCR / Student or subscribe to the Psychology Daily Digest and get new content delivered to your inbox!