SAQ's BIO The Brain and Behavior Genetics Flashcards
Aim Caspi
examined the role of the 5-HTT gene in depression, testing if people who inherited two short versions of the 5-HTT gene are more likely to develop depression after a stressful life event than people with two long alleles.
Procedure Caspi
Caspi used a sample of over 800 New Zealand 26-year-olds. The study was a correlational study. Participants were divided into three groups: Group 1 had two short alleles; Group 2 had one short and one long allele; Group 3 had two long alleles. The participants were asked to fill in a “Stressful life events” questionnaire. They were also assessed for depression.
Caspi results
- 2 short alleles+ 3 or more stressful life events = more likely to have depression
- simply inherting gene = not enough to inherit depression -> genes interaction with stressful life events increased likelihood of developing depression
- by inherting mutation -> one is more vulnerable to depression
Weissmann Aim
to study the potential genetic nature of Major Depressive Disorder
Weissman Procedure
- sample of 161 grandchildren and their parents and grandparents
- took place over twenty years, looking at families at high and low risk for depression
- the original sample of depressed patients (now, the grandparents) was selected from an outpatient clinic with a specialization in the treatment of mood disorders
- the non-depressed participants were selected from the same local community
- the original sample of parents and children was interviewed four times during this period
◦ the children are now adults and have children of their own - allowing for the study of the third generation - data was collected from clinicians, blind to past diagnoses of depression or to data collected in previous interviews
- to increase the credibility of the findings, researcher triangulation was used
◦ children were evaluated by two experienced clinicians - with one being a child psychiatrist and the other a psychologist
Weissman Findings
- high rates of psychiatric disorders in the grandchildren with two generations of major depression
- by 12 years old, about 59% of the grandchildren were already showing signs of a psychiatric disorder - most commonly anxiety disorders
- children had an increased risk of any disorder if depression was observed in both the grandparents and the parents, compared to children whose parents were not depressed
- if a parent was depressed but there was no history of depression in the grandparents, there was no significant effect of parental depression on the grandchildren
- the severity of a parent’s depression was correlated with an increased rate of mood disorders in the children
Wedekind Aim
Wedekind (1995) carried out a study to see to what extent MHC alleles play a role in mating behavior. They are inherited from both of our parents – and they are codominant. That means we end up with both immune systems. He argued that our “smell” is based on our MHC and it is best for a woman to choose a mating partner who has a different smell in order to maximize the immune system of her child.
Wedekind Procedure
Students were used in the study. The men were asked to wear a T-shirt for two nights. They were also told not to wear any perfume or perfumed soap, to avoid spicy food, smoking, and alcohol. They were told not to do anything that would change their natural smell.
Two days later the women were asked to rank the smell of the t-shirts. They were tested in the second week after the beginning of menstruation when they have a better sense of smell. T-shirts were placed into boxes with a “smelling hole.” 3 boxes contained t-shirts from men with the same MHC as the woman, three were different and one was unworn. Every woman rated the shirts for their “pleasantness.”
Wedekind results/link sentence
The women scored the t-shirts as more pleasant when the MHC was different than their own. This suggests that natural selection may play a role in human mate selection. If the woman’s mate has a different MHC allele, then both his allele and her allele will be inherited and expressed by a child, thus increasing its immune system and chances of survival.
Explain the role of one gene in one behaviour with reference to one study
The role of 5-HTT gene in depression. This gene plays a role in the serotonin pathways that scientists believe are involved in controlling mood, emotions, aggression, sleep, and anxiety. The long allele is the “normal” allele; the short allele is the mutation. Caspi et al examined this, and hypothesised that people who inherit two short versions of the 5-HTT gene are more likely to develop depression after a stressful life event.
Explain how genetic similarities help psychologists in the study of genes and behaviour with reference to one study
Before the Human Genome Project, psychologists were dependent on an indirect approach to studying the heritability of behavior. If the participants were genetically similar and had the same behavior – whereas those that were not genetically similar did not have the same behavior – then it was assumed that genes must be playing a significant role. These methods help to build a hypothesis, but they are limited in their explanation. Being able to map genes and their mutations has helped psychologists get a better understanding of the actual role of genes in behavior. in example of the depression, and that children’s who’s parents or grandparents had history with depression, they would be at an increased risk
Explain one evolutionary explanation of behaviour with reference to one study
Evolutionary arguments have been used to explain human mating behavior. Evolutionary psychologists argue that our behaviours are the result of natural selection – that means that the behaviors that most improve our chances of handing down our genes and producing healthy offspring have an evolutionary advantage. - Wedekind
Explain one ethical consideration in one study of genes and behaviour
Undue Stress or Harm, Caspi
An ethical consideration in one study of genes and behaviour is undue stress or harm in the Caspi study. The consideration of stress or harm in psychological studies refers to the protection from any stress/harm that a participant would encounter in everyday life. If unexpected stress does occur, or is unavoidable due to the nature of the study, researchers must minimise it as much as possible and provide appropriate support (i.e. debriefing or counselling).
The question is whether testing someone for the genetic mutation and informing them that this may make them more vulnerable to depression is undue stress. One could argue that it is not, but instead is a way to help people cope with the potential onset of depression. Knowing that you may develop it may help people to take more precautions like watching their diet or exercising on a regular basis.
Explain the use of one research method in one study of genes and behaviour
Weissman, longitudinal study,
- build up a more accurate and reliably ordered account of key events/experiences
- useful when studying developmental and lifespan issues because they allow glimpses into changes and possible reasons for them
Explain the use of kinship studies or twin studies in the study of inheritance of behaviour, making use of one study
Kinship studies are used in psychology to investigate the genetic basis of behavior by comparing biological relatives across multiple generations. These studies are based on the principle of genetic relatedness, which states that individuals who share a higher percentage of genes (e.g., parents and children, siblings) should have greater similarities in behavior if the trait being studied has a genetic component.
