Personality & Genetics: Molecular

Question 1

Estimating Environmental Influences: Describe shared factors

Answer 1

Are environmental factors that would be experienced the same by siblings growing up in the same family (I.e. they are factors that vary between families but not within.

Question 2

Estimating Environmental Influences: Describe non-shared factors

Answer 2

Are environmental factors that would be experienced differently by siblings growing up in the same family (factors that vary within families)

Question 3

The contribution of the shared environment to phenotypic resemblance can be inferred from what two types of studies?

Answer 3

MZ twin adoption studies
Non twin adoption studies

Question 4

In terms of MZ twin adoption studies, the correlation of MZ twins raised apart can be contrasted with the correlation for MZ twins raised together in the same family to show what?

Answer 4

If the shared environment contributes to phenotypic resemblance then the correlation for MZ twins raised together will be higher than the correlation for MZ twins raised apart.

Question 5

MZ twin adoption studies comparing Strong Campbell Vocational Interest for those raised together verses raised apart showed?

Answer 5

Environmental factors such as parental occupational status, socioeconomic status, parental attitudes towards education etc seem to increase the likelihood that siblings raised together will have more similar career aspirations than siblings raised apart

Question 6

MZ twin adoption studies comparing California Personality Inventory scores for those raised together verses raised apart showed?

Answer 6

That the shared environment does not make twins more alike in terms of their personalities

Question 7

MZ twin adoption studies comparing WAIS IQ scores for those raised together verses raised apart showed?

Answer 7

A correlation of .69 for reared apart indicates a high degree of heritability and the correlation of .88 for reared together indicates that the shared environment contributes considerably in terms of phenotypic resemblance.

Question 8

MZ twin adoption studies comparing Ravens Intelligence Test scores for those raised together verses raised apart showed?

Answer 8

With a correlation of .78 for raised apart versus. .76 for raised together this measure indicates that the shared environment doesn’t contribute to phenotypic resemblance. The Ravens Intelligence Test is considered the single best measure of fluid intelligence, thus fluid intelligence is entirely a function of shared genes.

Question 9

MZ twin adoption studies comparing those together verses raised apart showed what for the dimensions of Extraversion and Neuroticism?

Answer 9

The extent to which siblings are alike in terms of neuroticism and extraversion seems largely to be a function of shared genes rather than shared environment

Question 10

What can non twin adoption studies tell us in terms of phenotypic resemblance?

Answer 10

Adoption produces family members who share the family environment but no genetic relation. Thus, similarities estimate the contribution of shared environment to phenotypic resemblance.

Question 11

What do non-twin adoption studies suggest about the shared environment and the dimension of extraversion?

Answer 11

Being raised by extraverted adoptive parents does not increase the likelihood that adopted children will also be high on extraversion. The same is true of biologically unrelated siblings. Thus, extraversion is a function of shared genes.

Question 12

What do non-twin adoption studies suggest about the shared environment and the dimension of neuroticism?

Answer 12

Zuckermann’s review found a weak to moderate correlation between fathers and their adopted child as well as a weak to moderate correlation between adopted child and step siblings. Overall though the review showed shared environment is trivial.

Question 13

What is the MZ differences method used for?

Answer 13

It is used to estimate the non shared environmental contribution, focused on MZ twins raised together, singling out twins that are notably different from one another.

Question 14

When do genotype-environment interactions occur?

Answer 14

When people with different genotypes respond differently to the same environment.

Question 15

Name a study exploring the genotype-environment interaction, who were the participants, what was the gene variable and how was it measured? what was the environmental variable and how was it measured? And what was the dependent variable and how was it measured?

Answer 15

Haeffel et al (2008)
N = 176 male adolescent inmates sentenced to juvenile detention in northern Russia
Blood tests - Dopamine transporter gene DAT1 and the associated 3 variants (allele 1, allele 2, allele 3)
Maternal rejection measured by self report questionnaire (Own memories of parental Rearing scale)
DV = depression (assessed by 2 clinical Psychologists using a semi structured interview K-SADS-PL

Question 16

Why was the environment factor of high or low rejecting mother chosen by Haeffel et al?

Answer 16

As it is thought to be a risk factor for depression.

Question 17

What were. the findings by Haeffel et al?

Answer 17

They found no effect of gene alone and no effect of environment alone on levels of clinical depression.
The DAT1 genotype and maternal rejection contributed to the diagnosis of depression only in combination of one another.
Having a high rejecting mother was only a risk factor for depression for those carrying the allele 3 variant of DAT1

Question 18

A genotype-environment correlation is?

Answer 18

A genotype-environment correlation occurs when people with different genotypes are exposed to different environments depending on their genotype.

Question 19

Name the 3 possible reasons why we might get a genotype-environment correlation according to Polmin et al (1977)

Answer 19

• passive genotype-environment correlation
• evocative genotype-environment correlation
• active genotype-environment correlation

Question 20

A passive genotype-environment correlation occurs when parents passively provide both genes and an environment that correlates with the genes. Give an example

Answer 20

If musical ability is heritable, musically gifted children are likely to have at least one musically gifted parent who is immersed in a musical rich environment. Thus the child inherits both the gene and the musically rich environment that surrounds that parent.

Question 21

In terms of a passive genotype-environment correlation, explain why it isn’t just dumb luck as to why for example, a musically gifted child will be born into a musically rich environment.

Answer 21

A correlation suggests that there is a higher than chance probability that a child with musical giftedness ends up being born into a musically rich environment.

Question 22

Explain an evocative genotype-environment correlation

Answer 22

An evocative genotype-environment correlation occurs when individuals, on the basis of their genetic propensities, evoke reactions from other people.
- for example musically talented children might be picked out at school and given special opportunities, parents might enrol the child in music lessons etc

Question 23

Explain an active genotype-environment correlation.

Answer 23

Occurs when individuals select, modify, construct or reconstruct experiences that are correlated with their genetic propensities.
- even if no one does anything about their musical talent( evocative function) the child might on their own seek out musical environments by selecting or creating musical experiences.

Question 24

Describe a curious consequence of genotype-environment correlations.

Answer 24

Measures of the environment end up showing a genetic influence - because there is some genetic control over exposure to environmental influences (Polmin et al, 2002)
- a review of 55 independent genetic studies found an average heritability of .27 across 35 different environmental measures, including exposure to drugs, exposure to trauma, propensity to marry, marital quality, divorce, accidents in childhood
- for example, a child with the gene for risk taking is more likely to have accidents in childhood