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Heritability estimates versus large environmental effects: the IQ paradox resolved
1Brookings Institution, 1775 Massachusetts Avenue NW, Washington, DC 20036, USA. wdickens@brook.edu
Psychological Review
|May 31, 2001
Summary
High heritability of intelligence (IQ) doesn't rule out environmental impact. A new model shows how environment significantly shapes IQ, even with strong genetic influence, by matching environments to individuals' genetic predispositions.
Area of Science:
- Behavioral genetics
- Psychometrics
- Human intelligence
Background:
- High heritability estimates for IQ suggest limited environmental influence.
- Observed intergenerational IQ gains indicate significant environmental effects.
- A paradox exists between genetic and environmental explanations for IQ differences.
Purpose of the Study:
- To present a formal model of intelligence (IQ) determination.
- To reconcile high heritability with substantial environmental effects on IQ.
- To explain phenomena anomalous under standard IQ models.
Main Methods:
- Development of a formal model incorporating genetic and environmental factors.
- Modeling of IQ determination with environment-matching to individual IQs.
- Analysis of model's capacity to explain IQ variation and related phenomena.
Main Results:
- The model demonstrates that environment can have very large effects on IQ, even with high heritability.
- The model resolves the apparent paradox between genetic and environmental influences.
- The model accounts for several previously anomalous observations in IQ research.
Conclusions:
- Environmental factors play a crucial role in shaping intelligence (IQ), alongside genetics.
- A gene-environment matching process can explain substantial environmental influences on IQ.
- The proposed model offers a more comprehensive framework for understanding intelligence.