The heritability of IQ

Heritability estimates versus large environmental effects: the IQ paradox resolved.

Some argue that the high heritability of IQ renders purely environmental explanations for large IQ differences between groups implausible. Yet, large environmentally induced IQ gains between generations suggest an important role for environment in shaping IQ. The authors present a formal model of the process determining IQ in which people's IQs are affected by both environment and genes, but in...

Heritability of IQ by social class: evidence inconclusive.

.025), while the responses of the sham-operated were not significantly changed. After the operation the scores of the deganglionated group were significantly lower than the scores of the sham-operated group (P = .013). These results suggest that the siphon withdrawal component of the defensive reflex is mediated primarily by the central nervous system. This does not mean that all siphon withdra...

Socioeconomic status modifies heritability of IQ in young children.

Scores on the Wechsler Intelligence Scale for Children were analyzed in a sample of 7-year-old twins from the National Collaborative Perinatal Project. A substantial proportion of the twins were raised in families living near or below the poverty level. Biometric analyses were conducted using models allowing for components attributable to the additive effects of genotype, shared environment, an...

Direct and indirect IQ heritability estimates: a puzzle.

Direct estimates of IQ heritability based on a single family relationship such as adopted-apart relatives are often 50% greater than indirect estimates that rely on differences in correlations such as the classical twin method or nonadoptive-adoptive comparisons. Factors such as nonadditive genetic variance, assortative mating, selective placement, measurement error, age differences, and genoty...

A Very Little Bit of Knowledge: Re-Evaluating the Meaning of the Heritability of IQ