Summarise evidence from research on adoption, environmental deprivation or enrichment, and generational changes in IQ, showing how experience shapes intelligence.

Adoption studies show that children show at least some resemblance to their foster parents and that siblings reared together show more similar IQ scores than siblings reared apart. Environmental deprivation and enrichment studies show that children who are raised in substandard circumstances (understaffed orphanages and poverty) show erosion in IQ scores and the Flynn effect suggests that IQ performance has been steadily increasing all over the industrialised world. All of these results suggest that environmental factors may shape IQ performance.