More on Intelligence

 How stable are intelligence scores over the lifespan?  Casual observations and intelligence tests before the age of four only modestly predict a child’s future aptitudes  By four, intelligence tests do begin to predict adolescent and adult scores  High scoring adolescents tend to have been early readers  After age seven, scores stabilize  Consistency of scores increases over time! Stability or Change

Genetic and Environmental Influences

 Yes  There is no “intelligence” gene though; Intelligence is most likely polygenic  Genetic influences become more apparent the older we get  Adopted children’s intelligence scores over time become more like those of their biological parents Do Genes Influence Intelligence?

 Yes  Environment can enhance the scores of mistreated or neglected children  Fraternal twins’ scores are closer than with other siblings  Share a more similar environment  Schooling and intelligence interact…both enhance later income Does the environment influence intelligence?

 Heritability is the extent to which differences between people are the result of genetics  Example – Plants:  Put one group (randomly assigned) in enriched soil  Put another group in a nonrich environment  Results  Differences between groups will be a result of the environment  Differences WITHIN groups will most likely be due to genetics  Heritability of intelligence is 50%  Half of the differences in intelligence between people can be accounted for by genetic variance Heritability of Intelligence

 Intelligence test scores have been improving over the past century  By today’s standards, average intelligence score 80 years ago was 76  Why?  Greater test sophistication?  Better nutrition?  People have also gotten taller….  Greatest increases have been at lower socioeconomic status  From more education?  More stimulating environments?  Less childhood disease?  Smaller families and more parental investment? Flynn Effect