Genetics

Question 1

percentage of variance

Answer 1

the fact that individuals vary, an this variability can be partitioned into percentages that are due to different causes

Question 2

family studies method

Answer 2

• for traits with a large genetic component, the degree of similarity among relatives of that trait will be in proportion to the amount of genetic relatedness/degree of kinship among them
• ie. you’d be more similar to your siblings (50% shared genetics) than your grandparents (25% shared genetics) on a trait with a high genetic component
• limitation: similarity observed may also be due to shared environment (ie. your similarity to siblings may just be due to growing up in the same house w/same parents) -> no equal environments assumption

Question 3

twin studies on mental toughness

Answer 3

• mental toughness: important for academics, achievement, goal attainment, etc. -> involves commitment and control
• twin studies suggest genetics account for 54% of variance in mental toughness -> genetic and environmental element
• commitment component demonstrated greatest degree of environmentality -> implications for clinical interventions to increase it
• showed positive correlation with all Big 5 traits except neuroticism (negative correlation)

Question 4

adoption studies

Answer 4

• High correlations on traits between adoptive children and adoptive parents provide evidence of environmental influence
• High correlations between adopted children and genetic parents provide evidence of genetic influence
• Major strength: genetic parents are providing no environmental influences -> genetics and environment can no longer be confounded
• Limitation: selective placement (ex. Choosing a child that looks like them; can happen subconsciously) -> confounding of genes/environment

Question 5

behavioural genetics research on neuroticism and extraversion

Answer 5

• twin studies show that neuroticism and extraversion are very heritable (~50% genetics)
• adoption studies show slightly less evidence for heritability, and no direct evidence for environmentality (ie. extraverted adoptive parents don’t make their introverted children extroverted)

Question 6

behavioural genetics research on other traits

Answer 6

• activity level, emotionality, sociability, persistence, fear, distractibility show moderate heritability
• psychopathic traits show moderate-high heritability
• aggression shows high heritability

Question 7

Results from Minnesota Twin Studies

Answer 7

• most traits show modest degree of heritability (including ones we think are highly heritable and highly environmental)
• some attitudes show heritability (ex. conservatism), but some don’t (ex. religiosity)
• occupational preference influenced by heritability

Question 8

sexual orientation

Answer 8

• included as part of personality (though controversially) -> stable over time, associated with different life outcomes
• heritability varies (30-70%); is typically less than originally thought, but is partly heritable
• may be due to differences in hypothalamus or a gene on the X chromosome
• strongly related to childhood gender non-conformity (ie. feminine boys highly likely to be gay men)
• twins studies show low concordance (probability that if one twin is gay, the other will also be)

Question 9

what other things are heritable?

Answer 9

• drug use, alcoholism

- likelihood of marriage, divorce, marital quality

Question 10

influence of shared environmental influenced vs. unshared environmental influences

Answer 10

• Non-shared environments and genetics have much higher influence on personality than shared environments
• • Ex. Correlation of personality traits of adopted siblings (who share environments but not genes) is only .05 -> not causing personality similarities
• Shared environments tend to influence attitudes, religious beliefs, political orientations, health behaviours, etc. but NOT personality

Question 11

genotype-environment interaction

Answer 11

• different responses of people with different genotypes to the same environment -> Environment has a different impact depending on the person’s genotype
• • ex. introverts and extroverts responding differently to noisy environments
• • ex. Steve Jobs’ genes predisposed him to high assertiveness and low neuroticism, leading to him recovering after getting fired from Apple and starting a new business rather than withdrawing/failing

Question 12

genotype-environment correlation (and its 3 sub-types)

Answer 12

• exposure to environmental conditions depends on person’s genotype (ex. a highly intelligent kid might induce his parents to provide more intellectually stimulating environments for him, unlike a less intelligent kid; Steve Jobs’ creativity led him to create Apple)
• • passive gen.corr: seen in early childhood; parents provide genes & environment to kid without any action from kid (ex. buying books for smart kid)
• • reactive gen.corr: parents respond to kids differently based on genotype (ex. kid doesn’t like to be hugged, mom is less physically affectionate with him) -> same as evocation
• • active gen.corr: people seek out environments based on genotype (ex. smart people reading lots of books) -> same as selection

Question 13

molecular genetics

Answer 13

• methods designed to identify specific genes associated with personality traits
• ex. association method -> seeing whether individuals with a particular allele/gene are higher or lower in certain traits
• DRD4 gene is most frequently examined (codes for dopamine receptor, related to novelty-seeking)

Question 14

environmentalist view

Answer 14

personality is determined by socialization processes, such as parenting

Question 15

nature/nurture vs. person/situation debate

Answer 15

• Nature/person:
• • Person: individual differences or personality characteristics
• • Nature: genetic makeup
• Nurture/situation:
• • Very similar – environmental and contextual factors
• • Nurture focuses on childhood environment and parenting

Question 16

nature-nurture debate

Answer 16

• not a debate at the individual level -> what makes us who we are as individuals is ALWAYS a combo of genes and environment
• This is a question at the group/population level -> ex. Which is more important (genes or environment) in accounting for the differences we see in Trait X?
• Currently, most experts believe personality is influenced by both nature and nurture; still debate the degree to which biology and environment influence specific behaviours and traits (ex. Sexual orientation, aggression intelligence)

Question 17

insights from human genome project

Answer 17

• Only 2 candidate genes with evidence of influence on personality
• • Dopamine receptor gene DRD4 linked to novelty-seeking (among many psychiatric conditions)
• • Serotonin transporter gene 5-HTTLPR linked to neuroticism and other depressive and anxiety-related traits
• Conclusion: very many genes involved; no 1-to-1 relationships -> human personality is too complex

Question 18

Genes and traits/behaviour

Answer 18

• Almost everything is partially heritable: self-esteem, personality, IQ, sexual orientation, political & religious orientation, divorce
• No particular gene for each, but genes influence hormones/arousal, which influences thoughts/feelings, which influences personality

Question 19

heritability

Answer 19

• Proportion of observed variance in group of individuals that can be explained or accounted for by genetic variance
• Cannot be applied to an individual; not constant or absolute; not a precise statistic

Question 20

environmentality

Answer 20

• Proportion of observed variance in group of individuals attributable to environmental variance
• Greater the environmentality of a characteristic, the less the heritability

Question 21

twin studies (basics)

Answer 21

• Estimate heritability by gauging whether identical (monozygotic/MZ) twins who share 100% of genes are more similar than fraternal (dizygotic/DZ) twins, who share 50% of genes
• If MZ twins are more similar than DZ twins, this provides evidence of heritability
• One way to calculate heritability = Falconer’s Formula (determines proportion of variance due to genetic factors)

Question 22

2 assumptions of twin studies

Answer 22

• Representativeness assumption: twins are representative of the traits in the overall population
• Equal environments assumption: experiences of two identical twins are not more similar than the overall population

Question 23

heritability estimates of big 5

Answer 23

• Most heritable: openness -> Extraversion -> conscientiousness -> neuroticism & agreeableness
• Lots of variability of trait heritability within Big 5 traits

Question 24

design that combines strengths of twin and adoption studies

Answer 24

• MZ twins reared apart
• Neither of them live with biological parents, both adopted separately
• Look at degree of concordance between a trait – that’s its heritability

Question 25

heritability estimates of big 5 in MZ twins raised apart

Answer 25

- Higher heritability estimates found | - WHY? MZ twin adoption studies allowed estimates to be more precise

Question 26

environmental effects

Answer 26

- shared environmental effects: family and environmental influences that affect twins or siblings similarly (Ex. Parents' beliefs and attitudes, neighbourhood, number of books in home, time in front of TV, etc.) - non-shared environmental effects: family and environmental influences that affect twins or siblings differently (Ex. Birth order, changes in parenting style, unique experiences, etc.)

Question 27

genetic determinism vs. free will

Answer 27

- Do we have conscious control over our actions, thoughts, and personality? - free will may be influenced by genetics - Ex. Concordance rates of felony convictions are much higher between identical twins than fraternal twins