1. Genetic and Environmental Influence on Intelligence

2. Is it in the Genes?
Heritability – extent to which intelligence test score variation can be attributed to genetic variation (Is it inherited?)
Intelligence runs in families…Does that mean intelligence is inherited or fostered by our environment?
The big question…AGAIN…
What do you think would be the best way to test this?

3. Is it in the Genes? Twin & Adoption Studies
Intelligence test scores of identical twins raised together are as similar as the same person taking the test twice
Brain scans show identical twin brains are built and function similarly
Some genes have been identified, but intelligence involves many genes and the combinations

5. Twin & Adoption Studies
Does this chart support nature or nurture?

6. Or is it the environment?
Twin & Adoption Studies
Adoption enhances IQ scores of neglected children
When environment is varied, environment is more predictive of scores (often occurs with less-educated parents)

7. What do you think? Twin & Adoption Studies
Studies have compared biological/adoptive/ twins/not twins…
Do you think kids become mentally more like their biological parents or their adoptive parents?
Genetic influences, not environmental become more apparent with age

9. Environmental Influences
Genes make a difference, but life experiences do too
Early Environment
Studies of impoverished orphanages showed extreme deprivation destroys native intelligence
Low-economic schools often have less qualified teachers – leading to lower achievement scores
Malnutrition also contributes to the decline
No studies support any way to “fast forward” intellect
Study compared Baby Einstein users to control group = no difference in word-learning

10. Environmental Influences
Schooling and Intelligence
Schooling does enhance later income
College – study motivation and skills are as good as previous grades to determine academic achievement
Motivation – when promised money for doing well, adolescents score higher on tests
The brain is like any other muscle – it grows stronger as neuron connections grow