Adopted children (without any genetic links with their adoptive parents) have shown that non-genetic parents’ SES factors can impact the cognitive development of a child. The IQ of these children was measured before adoption, and all children, whether adopted by low- or high-SES families, had higher IQ’s after adoption. But children adopted by higher-SES families had significantly larger gains in IQ than children adopted in lower-SES families because they were raised in richer, more stimulating environments.