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36 Cards in this Set
- Front
- Back
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Describe DeFries et al.'s 1978 open field behaviour study measuring the effects of selective breeding on fearfulness |
30 generations of mice tested over 10 years 1. mouse if put in a box and its activity level is measured 2. high and low activity strains are selected 3. the mice in each strain were selectively bred but inbreeding was carefully avoided
Results: clear genetic effect, the highly active mice produced more highly active mice, and vice versa for less active mice a) 30-fold difference between high and low strains after 30 generations = incredibly inactive fearful mice vs. hyperactive mice
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What does the pattern of behavioural divergence in open-field studies suggest? |
Many genes are affecting open-field activity, not just 1 or 2 |
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What did Loehlin (1992) find in his cross-cultural study of heritability of personality characteristics? |
5 studies in 5 different countries 24,000 pairs of twins
Environmental effects are almost entirely due to non-shared environmental effects (i.e. those outside the family/home) Heritability for E- 50% and for N-40% |
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What did Loehlin's results from his heritability studies show about Big 5 heritability? |
Openness: 45% C: 38% A:35% |
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What explanations are there for why extroversion correlations between MZ twins were more than twice those between DZ twins? |
Loehlin, 1992 Non-equal environments? Genuine non-additive genetic effects |
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What is the assumption of additive genetics? |
There is a linear increase in trait similarity as the proportion of genes shared by the two individuals increases. This is 'narrow heritability' |
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What is broad heritability? |
The sum of additive and non-additive genetic effects |
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Give two examples of violations of the additive genetics assumption |
1. genetic dominance 2. epistasis/emergenesis |
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What are the three models used to explain MZ and DZ twin correlation discrepancies? |
1. genetic dominance 2. epistasis 3. equal environments (or lack thereof) |
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If there are significant dominance effects in the genetic contribution to E what does this imply in terms of the ratio of DZ:MZ correlations? |
The usual 1:2 ratio will not be applicable |
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What proportion of dominance genetic variation is shared by DZ and MZ twins respectively? |
25% and 100%
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Does the inclusion of a parameter for epistasis help the model fit the data better? |
Yes |
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Which quantitative model of Big 5 trait heritability fits the data best? |
All three fit equally well |
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Extroversion is made up of which 6 factors? |
sociability impulsiveness liveliness activity dominance sensation-seeking |
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What is the approximate heritability of sensation seeking? |
60% |
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Sensation seeking comprises which three factors? |
1. disinhibition (social riskiness) 2. thrill seeking (physical riskiness) 3. boredom susceptibility |
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Describe a multi-method analysis of personality variance explanations using the big 5 characteristics |
Riemann et al., 1997 Used 5 self report questionnaires and 2 peer ratings of twins
Peer rating correlations: 0.61 Peer-self correlations: 0.55 |
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What did Tellegen et al., 1988 find to be the heritability of broader traits like aggression, traditionalism and self-potency? |
0.50 |
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Which two personality traits seem to have disproportionate influence on the general genetic effects seen in personality variance? |
Neuroticism and extroversion |
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Give two examples of traits independent of E and N |
traditional masculinity/femininity tolerance of ambiguity
both show negligible heritability
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What did Loehlin, 1982, believe traditionalism was a measure of? |
conformity and conservativeness - the extent to which one follows rules and authority and endorses high moral standards and strict discipline |
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What is the spousal correlation of traditionalism? What is this evidence of? |
50% = assortative mating |
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What is the cafeteria model of acquisition of social attitudes? |
The cultural institution (e.g. family, school, culture, etc.) serves up a menu; the genes influence what you choose to put on your tray
- choices reflect what is offered and the person's own biases |
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Environmental variance is comprised of which two dimensions? |
That shared by family members That not shared by family members |
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What is the influence of non-shared environmental factors on adopted siblings on a) personality b) cognitive abilities |
personality: 0.05 cognitive abilities: 0.25 in childhood (0 in adolescence) |
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What exceptions are there in terms of traits that are less affected by non-shared environment than by shared-environment effects. |
1. attitudes 2. beliefs 3. delinquency 4. vocabulary |
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What intra-familial differences account for small proportions of variability in intelligence and other traits? |
birth order sibling age spacing gender differences |
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What are non-systematic factors? Give examples and say what effects they might have. |
1. Factors that are unique to the individual and are not part of a family environment, a peer environment or genetics 2. For example, accidents and illnesses 3. When compounded over time, they make children in the same family difference in unpredictable ways |
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What are the 3 types of gene-environment covariation (i.e. how do genetics affect environment) |
1. passive: parental behaviour is determined by their IQ and may alter physical environmental features, e.g. number of books in the home 2. reactive: parental responses to characteristics of child's personality - e.g. precocious child might be read to more often 3. active: child seeks out friends and situations to reinforce their genetic differences - e.g. spends more time in the library
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What correlations in non-adoptive vs adoptive families would indicate that genetics are mediating the environment effect? |
If non-adoptive family correlations are greater than those within adoptive families |
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Give 5 differences between linkage and association studies: |
Linkage require families, Associations don't
Linkage: matching/ethnicity unimportant Association: matching/ethnicity important
Linkage: weak design and few markers for genome coverage Association: powerful design and many markers for genome coverage
Linkage: powerful for rare variants Association: powerful for common variants |
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What does QTL stand for? |
quantitative trait loci
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Define 'pleiotropy' |
a gene could have influence on 2 or more phenotypes |
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Describe the genetic basis of neuroticism as a personality trait |
N linked to neurotransmitter serotonin (5-HT) Single gene on chromosome 17 codes for the 5-HT transporter (5-HTT) There are two alleles of this gene, short (high N) and long (low N) This has implications for anxiety and depression |
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Outline quantitative vs. molecular genetics |
Quantitative: estimating relative contributions of genes and environments to variation in a trait or covariation between traits
Molecular: finding the associated genes |
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Outline functional vs. behavioural genomics |
Functional: once a gene is found, understanding how it works using a bottom-up molecular biological approach that begins with the gene product in a cell
Behavioural: a top-down level of analysis that begins with the behaviour of the whole organism |
