Chap 6: Genetics and Personality Flashcards
Human Genome def.
The complete set of genes that an organism possesses
of genes on # of pairs of chromosomes
The human genome contains:
- 20,000-30,000 genes on…
- 23 pairs of chromosomes
Similarities in genes in human genome
- most genes in human genome are the same for all humans
- small # of genes are different for different individuals, including genes that indirectly code for physical traits and for personality traits
Controversy about genes and personality
- Determine the degree to which individual differences in personality are caused by genetic and environmental differences
- Highly controversial:
1. Ideological concerns (political agendas-crimes)
2. Concerns about renewed interest in eugenics - Finding that a personality trait has a genetic component does not mean that the environment is powerless to modify it
Three Goals of Behavioral Genetics
- Determine the % of individual differences in a trait that can be attributed to genetic differences and % environmental differences
- Determine the ways in which genes and the environment interact and correlate to produce individual differences
- Determine precisely where in the “environment” environmental effects exist
Two Definitions of Heritability
- Proportion of observed variance in a group that can be explained by genetic variance
- Proportion of phenotypic variance that is attributable to genetic variance
Phenotypic Variance def
Difference in observable characteristics
Environmentality
Proportion of observed variance in a group of individuals attributable to environmental variance
Three Misconceptions of Heritability
- Heritability CANNOT be applied to a single individual
- Heritability IS NOT constant or immutable
- Heritability IS NOT a precise statistic
Nature-Nurture Debate Clarified
No debate at individual level, environmental influence is only relevant at group-level
Four Behavioral Genetics Methods
- Selective Breeding
- Family Studies
- Twin Studies
- Adoption Studies
Selective Breeding
- Can only occur if a desired trait is heritable
- Not ethically conducted on humans
- Dogs example
Family Studies
- Correlates the degree of genetic overlap among family members with the degree of similarity in a personality trait
- Problem: members of a family who share the same genes also usually share the same environment
- So, family studies are never definitive
Twin Studies
- Estimates heritability by gauging whether identical twins (monotygotic/100% same genes) are more similar that fraternal twins (dizygotic/50% same genes)
- Two assumptions:
1. equal environments assumption
2. representativeness assumption - if MZ more similar than DZ this provides evidence of hereditary
Adoption Studies
- correlation between adopted children and adoptive parents = environmental influence
- correlation between adopted children and genetic parents = genetic influence
- powerful because it gets around equal environments assumption
Attitudes and Preferences
- Wide variance in heritability of attitudes
- Genes appear to influence occupation (on a broad field spectrum)
Genetic Influence on Risk of Divorce
- Divorce was significantly higher in MZ twins than DZ twins
- This indicates a strong influence of genetic factors in the etiology of divorce
Shared vs nonshared environmental influences
- two key types of environmental influences:
1. shared: features of the (family) environment shared by siblings (# of books in home)
2. nonshared: features of the (family) environment that differ across siblings (friends, teachers, activities) - for most personality traits, the shared environment has little impact
- parents have no effect on personality
Genes and the environment: two issues
- genotype-environment interaction
2. genotype-environment correlation
Genes and the environment:
genotype-environment interaction
- Differential RESPONSE of individuals with different genotypes to the SAME environment
- example: task performance of introverts vs extroverts in noisy vs quiet conditions
Genes and the environment:
genotype-environment correlation
- Differential EXPOSURE of individuals with different genotypes to DIFFERENT environments
- Three types:
1. Passive: parents provide genes and environment but children do nothing to obtain that environment
2. Reactive: parents respond to children differently depending on a child’s genotype
3. Active: person with particular genotype seeks out a particular environment
Molecular Genetics
- Techniques designed to identify specific genes associated with personality traits
- D4DR - gene located on short arm of chromosome 11 associated with novelty seeking
