Summary #7 nature vs. nurture
Behaviorial genetics
= individual differences due to genetics and environment
Goal
determine extent to which individual differences can be attributed to
Genetic differences
Environmental differences
A combination of differences
Aim of research
how do genes & environment interact/correlate?
Eugenics
= design the future by selective breeding.
Genetic differences
heritability
= observed variance in a group of individuals that can be accounted for by genetic
differences (statistical)
heritability index
= estimate of the role of heritability in accounting for individual differences (how much
phenotype can be attributed to genotype)
cannot be applied to individual, only to a population.
can be subject to unreliable measurements (self-report)
is not always generalizable (counts only for the specific test population)
merely statistic (no mechanics of genetic influence)
extraneous variables (not environment/genetic)
heritability varies with time/environment
experiment:
Parents less educated + influence environment
Parents more educated + influence heritability
Behavioral genetic methods to research gene-environment interactions
1. Selective breeding
= artificial selection (dogs/nazi germany)
2. Family studies
= look at correlation between family member
they do share same environment (mainly)
3. Twin studies
= use of two types of twins
Monozygotic/identical
100% same DNA
Dizygotic/fraternal
50% same DNA
, 1. Compute correlation between
Mz twins
Dz twins
2. Compare correlations
3. If MZ twins correlate more + heritability
Or use formula h2= 2 (r(mz) – r(dz)
More heritability genes matter more/are more important
Twin studies are based on the
Equal environment assumption
Both mz & dz twins experience the same ‘shared’ environment.
Shared environment
Environment/experiences the people (twins/siblings) share makes them more a like
Unique/unshared environment
Special/different treatment from people (even parents)
Accidents/illnesses
Interactions with outside world (peers, social support, educational, occupational,
interpersonal experiences.
the environment mostly has an influence on individuals NOT the same influence on the
whole family.
It is mostly the unshared environment that shapes the person and is responsible for many
differences between people (twins).
It is however proven that; identical twins still show the same strong correlations even when
they’re not treated/perceived/reacted to as being identical twins.
(conditions were created when accidentally not being aware of being mz twins)
equal environment assumption is accepted
RESULTS:
MZ twins do correlate stronger (strongest when raised together) than DZ twins on
personality characteristics/BIG 5 traits.
Behaviorial genetics
= individual differences due to genetics and environment
Goal
determine extent to which individual differences can be attributed to
Genetic differences
Environmental differences
A combination of differences
Aim of research
how do genes & environment interact/correlate?
Eugenics
= design the future by selective breeding.
Genetic differences
heritability
= observed variance in a group of individuals that can be accounted for by genetic
differences (statistical)
heritability index
= estimate of the role of heritability in accounting for individual differences (how much
phenotype can be attributed to genotype)
cannot be applied to individual, only to a population.
can be subject to unreliable measurements (self-report)
is not always generalizable (counts only for the specific test population)
merely statistic (no mechanics of genetic influence)
extraneous variables (not environment/genetic)
heritability varies with time/environment
experiment:
Parents less educated + influence environment
Parents more educated + influence heritability
Behavioral genetic methods to research gene-environment interactions
1. Selective breeding
= artificial selection (dogs/nazi germany)
2. Family studies
= look at correlation between family member
they do share same environment (mainly)
3. Twin studies
= use of two types of twins
Monozygotic/identical
100% same DNA
Dizygotic/fraternal
50% same DNA
, 1. Compute correlation between
Mz twins
Dz twins
2. Compare correlations
3. If MZ twins correlate more + heritability
Or use formula h2= 2 (r(mz) – r(dz)
More heritability genes matter more/are more important
Twin studies are based on the
Equal environment assumption
Both mz & dz twins experience the same ‘shared’ environment.
Shared environment
Environment/experiences the people (twins/siblings) share makes them more a like
Unique/unshared environment
Special/different treatment from people (even parents)
Accidents/illnesses
Interactions with outside world (peers, social support, educational, occupational,
interpersonal experiences.
the environment mostly has an influence on individuals NOT the same influence on the
whole family.
It is mostly the unshared environment that shapes the person and is responsible for many
differences between people (twins).
It is however proven that; identical twins still show the same strong correlations even when
they’re not treated/perceived/reacted to as being identical twins.
(conditions were created when accidentally not being aware of being mz twins)
equal environment assumption is accepted
RESULTS:
MZ twins do correlate stronger (strongest when raised together) than DZ twins on
personality characteristics/BIG 5 traits.
