PSY 111 Chapter Notes - Chapter 32: White Matter, Malnutrition, Heritability
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Chapter 32: Genetic and Environmental Influences on Intelligence
I. Twin and Adoption Studies
A. Things to consider:
1. The intelligence
test scores of identical twins who are raised together are
as similar as those of the same person taking the same test twice.
2. Heritability: extent to which intelligence test score variation can be
attributed to genetic variation
3. Scans show that identical twins’ brains have similar grey and white matter
and that the areas are associated with verbal and spatial intelligence.
4. Studies show that adoption enhances the intelligence scores of
mistreated or neglected children.
B. Genetic influences become more obvious as we accumulate life experience.
II. Environmental Influences
Human environments are as impoverished as the dark and barren cages inhibited by
deprived rats that have thin brain cortexes.
A. Early Environmental Influences
1. By 22 months of age, infants would name more than fifty objects and
2. Poor environmental conditions can depress cognitive development.
3. Poverty related stresses also impede cognitive performance.
4. Malnutrition also plays a role. It can retard normal brain development.
B. Schooling and Intelligence
1. School is one intervention that pays intelligence score dividends.
2. Schooling and intelligence interact and both enhance later income.
3. Studies recommend that having a head start increases school readiness
and provides a boost to later health and high school completion rate.
4. Intelligence scores also rise with nutritional supplements to pregnant
moms and newborns.
5. Study motivation and study skills rivaled aptitude and previous grades as
predictors of academic achievement. Motivation can even affect
intelligence test performance.
6. Real world studies confirm: ability + opportunity + motivation =
III. Group Differences in Intelligence Test Scores
A. Gender Similarities and Differences
1. Difference excite interest.
2. Girls outpace boys in spelling, verbal fluency, locating objects, detecting
emotions, and sensitivity.
3. Boys outperform girls in tests of spatial ability and complex math
4. Boys worldwide outnumber girls at both the low and high extreme
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