1. What do adoption studies teach us that twin studies cannot?
Adoption studies allow us to study an individual within the same environment as others, but that has different genetic material than the rest of the family.
2. How might we explain the fact that the concordance rates for behaviours in identical twins is rarely 100%?
There are several reasons why the concordance rate may not be 100%. One reason has to do with gene expression. It may be that both twins have the genes for a behaviour, but that not all of the genes are expressed, so that behaviour is not observed. This does not mean, however, that there is not a genetic root to the behaviour.
It could also have to do with the way the behaviour is measured. Often behaviour is self-reported - for example, one's sexuality. Or it is based on a diagnosis. In that case, it may be that the diagnosis was not valid, or that some of the controls actually may have the disorder, but have not gone for diagnosis.
Finally, it could be that there are purely environmental factors that play a role in the behaviour; however, until we are able to better map the functions of the 22.000 human genes, we cannot 100% support this response, since a lack of gene expression cannot be ruled out.
3. Construct validity is often a problem in genetic studies. Explain by giving an example.
When investigating the genetic origin of a behaviour, it is important that psychologists agree on the definition of the behaviour. If, for example, in Caspi's study the researchers asked if the participants had a diagnosis of depression, we have to assume that the diagnosis was valid in order for the study's findings to be valid. In Bailey and Pillard's study, we have to assume a common understanding of "homosexuality" or in studies like Christiansen's study of criminal behaviour, we have to have a common understanding of how the variable (criminal behaviour) is being defined and measured.
4. Genetic research uses a "reductionist approach." Is this a good approach?
Genetic arguments are reductionist by nature - that is, they are trying to take a complex behaviour and "reduce" its origin down to a gene or (more likely) a set of genes. This, however, is not a problem. Medicine is based on finding the "cause" of disorders and finding a single cause is not in and of itself a bad thing. When researchers ignore other possible causes, then this is problematic. In the case of modern genetic research, researchers acknowledge the gene-environment interaction - that is, that genes are expressed by interaction with the environment. This makes the argument more complex than simply "finding a gene."
5. How did the Human Genome Project revolutionize our ability to understand the role of genetics in human behavior?
The Human Genome Project mapped out our genes, taking us from simple twin studies, to actually comparing genetic material. Twin studies are helpful even today in determining whether there is any potential genetic basis to a behaviour, but they are limited in that it is only a behavioural correlation. The HGP has allowed us to start looking at specific gene combinations which may play a role in behaviour.
6. Caspi’s study is often used as an example of the Diathesis-Stress model. What does that mean?
The Diathesis-Stress Model is a psychological explanation of abnormal behaviour based on gene expression. The theory says that some of us have a "genetic vulnerability" to a disorder. Exposure to stressors may lead to gene expression which then leads to the onset of a disorder.
7. What is the key advantage of Genome Wide Association Studies (GWAS)?
A GWAS is based on a large amount of aggregate data - often hundreds of thousands of samples of both control and "target behaviours." By using such a large amount of data, the effect of outliers do not have an undue effect on the data.
8. What are the limitations of using pedigree (family) studies?
Pedigree studies examine behaviours through a family tree. There are several problems with this. Often older generations were not diagnosed with disorders such as anorexia or Alzheimer's disease. Since these diagnoses were not common, there may be a degree of speculation - or even memory distortion - in creating the family history, rather than hard data. Pedigree studies tend to work best for physical traits, rather than behaviours.
As people are waiting later to have families, fewer generations can be studied easily. This is why biologists like to study animals - they can observe behaviours over several generations in a relatively short period of time.
IB Docs (2) Team
The following page is to revise the key concepts, research and critical thinking for the topic "the role of genetics in behaviour." The revision focuses on several different behaviours - depression, sexuality, obesity and criminal behaviour.
Twitter
Facebook
LinkedIn