Behavioural genetics deals with understanding how both genetics and the environment contribute to individual variations in human behaviour. We inherit our genetic material – that is, DNA – from our parents. However, when psychologists argue that behaviour may be inherited, what exactly does that mean? What is inherited is the genes that give rise to the development of specific physiological processes that contribute to specific traits and behaviour. It is not probable that a single gene is responsible for such complex behaviours as intelligence, criminal behaviour, altruism, or attachment. Instead, what is inherited may be the building blocks for such complex behaviours.

Psychologists argue that an individual may have a genetic predisposition towards a certain behaviour; however, without the appropriate environmental stimuli, the gene is not “turned on” and the behaviour is not expressed.

For example, in the study of abnormal behaviour, the diathesis-stress model is used to explain the origin of depression. This model argues that depression may be the result of the interaction of a “genetic predisposition” and environmental stress. The model predicts that an individual with certain genes, when exposed to a stressful environment, is more likely to develop depression than someone who does not have those genes. This knowledge has been useful in understanding why not all people develop depression following a traumatic childhood, even if they have a sibling who becomes depressed. It also illustrates the complexity of the problem and that there is no single cause-and-effect relationship between genes and behaviour.

Genetic arguments of behaviour are based on the principle of inheritance. Genes and their DNA are passed down from parents to their offspring, with 50% of our genes being inherited from each parent. Humans have 23 pairs of chromosomes, with approximately 20.000 – 25.000 genes. We now know this number as a result of the worldwide research initiative started in 1990 called the Human Genome Project. The goal of this project was to map and sequence the human genome. This incredible project was completed in 2004. However, although the mapping of human genes could be an important step in understanding the complexity of human behaviour, as well as developing treatments for specific disorders, the exact role of specific genes in many behaviours remains unknown. Although you can undergo genetic testing for some medical conditions, the same is not entirely true for a disorder like depression.

Checking for understanding

Methodology in genetic research