Genetic and Environmental Influences on Intelligence
Heredity and intelligence
● Heritability refers to how much differences among people are due to genes.
● Behavior geneticists are most likely to use twin and adoption studies to
assess the heritability of intelligence.
● When researchers examined almost 270,000 people, they found that the
heritability related to educational achievement was roughly 5 percent.
● The heritability of intelligence is highest among genetically different
individuals who have been raised in similar environments.
● Intelligence test scores differ the most between nontwin siblings raised
together.
Environment and intelligence
● Research on the determinants of intelligence indicates that both genes and
environment have some influence on intelligence scores.
● The heritability of intelligence among children of less-educated parents is
relatively low because of the relatively large differences in their environmental
settings.
Group differences in intelligence test scores
● In cultures where both boys and girls are educated, girls tend to do better
than boys in spelling, reading, and locating objects.
● In Asia and Russia, teenage girls have scored higher than boys in an
international science exam; in North America and Britain, teenage girls have
scored lower than boys.
● Because group differences in a heritable trait may be entirely environmental,
they tell us nothing about individual differences in intelligence.
● Compared with North American students, students in Asia score higher on
math achievement tests and spend more time studying math in school.
Heredity and intelligence
● Heritability refers to how much differences among people are due to genes.
● Behavior geneticists are most likely to use twin and adoption studies to
assess the heritability of intelligence.
● When researchers examined almost 270,000 people, they found that the
heritability related to educational achievement was roughly 5 percent.
● The heritability of intelligence is highest among genetically different
individuals who have been raised in similar environments.
● Intelligence test scores differ the most between nontwin siblings raised
together.
Environment and intelligence
● Research on the determinants of intelligence indicates that both genes and
environment have some influence on intelligence scores.
● The heritability of intelligence among children of less-educated parents is
relatively low because of the relatively large differences in their environmental
settings.
Group differences in intelligence test scores
● In cultures where both boys and girls are educated, girls tend to do better
than boys in spelling, reading, and locating objects.
● In Asia and Russia, teenage girls have scored higher than boys in an
international science exam; in North America and Britain, teenage girls have
scored lower than boys.
● Because group differences in a heritable trait may be entirely environmental,
they tell us nothing about individual differences in intelligence.
● Compared with North American students, students in Asia score higher on
math achievement tests and spend more time studying math in school.
