SAQ's BIO The Brain and Behavior Genetics

Question 1

Aim Caspi

Answer 1

examined the role of the 5-HTT gene in depression, a gene known as a “serotonin transporter” gene, which regulates the level of serotonin in the synapse.

Question 2

Procedure Caspi

Answer 2

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.

Question 3

Caspi results

Answer 3

• People who had inherited one or more short versions of the allele demonstrated more symptoms of depression and suicidal ideation in response to stressful life events
• The effect was strongest for those with three or more stressful life events
• Simply inheriting the gene was not enough to lead to depression, but the genes interacting with stressful life events increased one’s likelihood of developing depression

Question 4

Weissmann Aim

Answer 4

to study the potential genetic nature of Major Depressive Disorder

Question 5

Weissman Procedure

Answer 5

• 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

Question 6

Weissman Findings

Answer 6

• high rates of psychiatric disorders in the grandchildren with two generations of major depression
• by 12 years old, about 60% 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
• the severity of a parent’s depression was correlated with an increased rate of mood disorders in the children
• 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

Question 7

Wedekind Aim

Answer 7

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.

Question 8

Wedekind Procedure

Answer 8

• double-blind experiment
  ◦ neither the researcher nor the participants were aware of which t-shirt they were being exposed to at any point in the study in order to minimize researcher bias in the experimenters and demand characteristics in the participants
• recruited a group of 49 women and 44 men, with a wide range of MHC genes
• gave each man a clean T-shirt and asked him to wear it for two nights
• To ensure a strong body odor, he gave the men supplies of odor-free soap and aftershave and asked them to remain as “odor neutral” as possible
  ◦ they were also forbidden to eat spicy food.
• After the men returned the shirts, Wedekind put each one in a plastic-lined cardboard box with a sniffing hole on top.
• The women were scheduled to return at the midpoint of their menstrual cycle when women’s sense of smell is at its best, and each was presented with a different set of seven boxes.
  ◦ Three of the seven boxes contained T-shirts from men with MHC similar to the woman’s own
  ◦ three contained T-shirts from MHC-dissimilar men; and one contained an unworn T-shirt as a control. The women were asked to rate each of the seven T-shirts as pleasant or unpleasant.

Question 9

Wedekind results/link sentence

Answer 9

• the women he tested were more likely to prefer the scent of men with dissimilar MHC
• although we might argue that this is strong evidence that MHC determines whom we find to be attractive, that would be a reductionist approach to relationships.

Question 10

Explain the role of one gene in one behaviour with reference to one study

Answer 10

the role of 5-HTT gene in depression

Question 11

Explain how genetic similarities help psychologists in the study of genes and behaviour with reference to one study

Answer 11

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

Question 12

Explain one evolutionary explanation of behaviour with reference to one study

Answer 12

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

Question 13

Explain one ethical consideration in one study of genes and behaviour

Answer 13

Caspi,undue harm or stress - 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.

Question 14

Explain the use of one research method in one study of genes and behaviour

Answer 14

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

Question 15

Explain the use of kinship studies or twin studies in the study of inheritance of behaviour, making use of one study

Answer 15

kinship/family studies
uses the principle of genetic relatedness, but compares relatives on a broader scale and across generations (e.g. siblings, grandparents, parents, cousins, aunts and uncles).

Weissman, used to establish a genetic argument for the origin of human behaviour, using correlational research.

Characteristics:
- They measure the frequency of a behavior across generations.
- They measure the frequency of a behavior within a generation.
- They are often longitudinal.
- They use case-control studies. Case-control studies are retrospective. They clearly define two groups at the start: one with the behavior/disorder and one without the behavior/disorder. They look back to assess whether there is a statistically significant difference in the rates of exposure to a defined risk factor between the groups - in this case, to potential genetic inheritance.