does iq grow with age

Introduction

The relationship between age and intelligence quotient (IQ) has been a subject of extensive research. Various studies have explored how IQ changes over time, the factors influencing these changes, and the role of genetic and environmental factors.

Key Insights

Heritability of IQ Increases with Age:
- The heritability of IQ increases as individuals age, reaching an asymptote of about 0.80 by 18-20 years and remaining stable into adulthood. Shared environmental influences decrease over time, approximating about 0.10 by 18-20 years.
Impact of Early Brain Growth on Later IQ:
- Brain growth during infancy, particularly head circumference at 8 months, is a significant predictor of IQ at 3 years of age. This relationship holds even when controlling for medical and sociodemographic variables.
- Prenatal head growth and growth during infancy are associated with higher IQ at ages 4 and 8. However, head growth after infancy does not significantly compensate for poorer earlier growth.
IQ and Cognitive Abilities Differentiation in Childhood:
- Age moderates the effect of IQ on the differentiation of cognitive abilities during childhood. The strength of relationships among cognitive subtests evolves with age, indicating that cognitive abilities become more distinct as children grow older.
Growth and Decline of Intelligence in Retardates:
- For individuals with intellectual disabilities, mental age (MA) grows linearly up to about 16 years of chronological age, after which it plateaus. The rate of MA growth is directly related to the level of intellectual disability, with higher-level retardates continuing to grow in MA for longer periods.
Age and IQ Effects on Timing Tasks:
- In older adults, increasing age and decreasing IQ are associated with greater variability in timing tasks. However, older adults can still perform these tasks accurately on average, suggesting that while cognitive processing speed may decline, basic timing abilities remain intact.

Conclusion

The research indicates that IQ is influenced by a combination of genetic and environmental factors, with heritability increasing with age. Early brain growth, particularly during prenatal and infancy periods, plays a crucial role in determining later IQ. While cognitive abilities become more distinct with age in children, the growth of intelligence in individuals with intellectual disabilities follows a linear pattern until it plateaus in late adolescence. In older adults, cognitive processing speed may decline, but basic timing abilities remain relatively stable.

Does iq grow with age

Summary

Consensus Meter

Introduction

Key Insights

Conclusion

Sources and full results

Very low birth weight infants: effects of brain growth during infancy on intelligence quotient at 3 years of age.

Brain growth at 8 months significantly influences IQ at 3 years of age in very low birth weight infants, even when medical and sociodemographic factors are controlled.

The Wilson Effect: The Increase in Heritability of IQ With Age

The heritability of IQ increases with age, reaching an asymptote of 0.80 at 18-20 years of age and continuing at that level well into adulthood, while shared environmental influence decreases across age.

Does age moderate the effect of IQ on the differentiation of cognitive abilities during childhood

IQ-related differentiation in cognitive abilities occurs during childhood, with higher IQ individuals showing stronger relationships among subtests as they age.

Growth and Decline of Retardate Intelligence1

Retardate intelligence grows linearly between 5 and 16 years, with higher levels continuing to grow for longer periods of life, while lower levels flatten out earlier.

Age and IQ effects on stimulus and response timing

Increased age and decreasing IQ tend to increase variability in judgments of duration, but overall accuracy in timing tasks remains generally consistent across groups.

The Influence of Head Growth in Fetal Life, Infancy, and Childhood on Intelligence at the Ages of 4 and 8 Years

Brain volume achieved by the age of 1 year helps determine later intelligence, with growth in brain volume after infancy potentially not compensating for poorer earlier growth.

The impact of childhood intelligence on later life: following up the Scottish mental surveys of 1932 and 1947.

Childhood intelligence has a significant impact on survival and health in old age, with stable IQ scores from age 11 to 80, sex differences in cognitive aging, and a dedifferentiation hypothesis of cognitive aging.

Genetic influences on childhood IQ in 5‐ and 7‐year‐old Dutch twins

Genetic factors significantly increase their influence on childhood IQ from age 5 to age 7, explaining 62% of the variance in IQ scores.

THE STABILITY OF INTELLIGENCE IN SMALL FOR GESTATIONAL AGE (SGA) CHILDREN AS A FUNCTION OF HEAD GROWTH DURING THE FIRST YEAR OF LIFE • 1162

Poor head growth in SGA children during the first year of life may predict declining IQ over time, but further research is needed.

Growth in early life and childhood IQ at age 11 years: the Newcastle Thousand Families Study.

Post-natal growth, influenced by genetic factors, nutrition, and socioeconomic circumstances, continues to influence childhood cognition beyond the age of 9.

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