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Genetic influence on general mental ability increases between infancy and middle childhood
D W Fulker1, J C DeFries, R Plomin
1Institute for Behavioural Genetics, University of Colorado, Boulder 80309-0447.
Nature
|December 22, 1988
Summary
This longitudinal adoption study tracked 245 children, revealing that heritable variation in general mental ability increases significantly from 9% at age 1 to 36% by age 7.
Area of Science:
- Behavioral genetics
- Developmental psychology
- Human heredity
Background:
- Adoption studies disentangle genetic and environmental influences on traits.
- Family environment and heredity are typically confounded in intact families.
- Longitudinal designs track developmental changes in these influences.
Purpose of the Study:
- To examine the independent effects of heredity and family environment on behavioral development.
- To investigate changes in genetic and environmental contributions over time.
- To analyze data from the Colorado Adoption Project over 7 years.
Main Methods:
- Longitudinal adoption study design.
- Recruitment of 245 adopted children and 245 matched non-adopted children.
- Data collection from biological parents, adoptive parents, and children at multiple ages (1-7.4 years).
Main Results:
- Heritable variation in general mental ability increases with age.
- Genetic influences grew from 9% at 1 year to 36% at 7 years.
- Provides evidence for increasing genetic determination of cognitive abilities.
Conclusions:
- Heritability of general mental ability shows a significant developmental increase.
- Adoption studies offer crucial insights into nature vs. nurture dynamics.
- The Colorado Adoption Project provides robust longitudinal data on behavioral development.