how much does iq increase with age

Introduction

The relationship between IQ and age has been a subject of extensive research. Various studies have explored how IQ changes over time, the factors influencing these changes, and the implications of these changes on cognitive abilities and mental health.

Key Insights

Heritability of IQ Increases with Age:
- The heritability of IQ increases with age, reaching an asymptote at about 0.80 by 18-20 years and continuing at that level into adulthood. Shared environmental influences decrease over time, approximating about 0.10 by 18-20 years and remaining stable into adulthood.
Impact of Early Brain Growth on IQ:
- Brain growth, particularly head circumference at 8 months, significantly influences IQ at 3 years of age among very low birth weight infants. This effect persists even when controlling for medical and sociodemographic variables.
Stability and Change in Intelligence Over Time:
- Intelligence shows both stability and change from age 12 to age 52. While the rank ordering of individuals' intelligence levels remains stable, the variance in general cognitive ability (g) increases, leading to a widening gap in cognitive abilities over time.
Sex Differences in IQ Over Time:
- At ages 7 and 11, girls have a slight IQ advantage over boys. However, by age 16, boys show a slight IQ advantage over girls.
Intelligence in Youth and Mental Health at Age 50:
- Higher intelligence in youth is associated with a reduced risk of self-reported mental health problems at age 50, such as depression and sleep difficulties. However, higher youth intelligence is also linked to an increased risk of receiving a diagnosis of depression by age 50.

Conclusion

The research indicates that IQ is influenced by a combination of genetic and environmental factors, with heritability increasing and environmental influences decreasing with age. Early brain growth plays a crucial role in determining IQ in early childhood. Over a lifetime, while the rank ordering of intelligence remains stable, the variance in cognitive abilities increases, leading to a widening gap. Additionally, sex differences in IQ can shift over time, and higher intelligence in youth has complex associations with mental health outcomes in later life.

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How much does iq increase with age

Summary

Introduction

Key Insights

Conclusion

Sources and full results

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.

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.

Stability and change in intelligence from age 12 to age 52: results from the Luxembourg MAGRIP study.

Intelligence levels increase from age 12 to age 52, with all broad abilities showing greater gap-widening effects and more closely related to each other at age 52.

A longitudinal study of sex differences in intelligence at ages 7, 11 and 16 years

At age 16, boys have an IQ advantage of 1.8 IQ points over girls, supporting Lynn's hypothesis that males develop higher average intelligence than females.

Intelligence in youth and mental health at age 50

Higher intelligence in youth is associated with reduced self-reported mental health problems at age 50, but an increased risk of depression by the age of 50.

The relationship between age and IQ in adults with Williams syndrome.

Adults with Williams syndrome show a stable overall IQ, but Performance IQ increases with age, suggesting that overall IQ may remain stable.

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.

Childhood IQ and survival to 79: Follow-up of 94% of the Scottish Mental Survey 1947

Higher childhood IQ is associated with lower risk of all-cause mortality in both men and women, with a slightly stronger effect in women and before age 65.

Predicting IQ Change in Preschoolers with Developmental Delays

Initial diagnosis may help predict IQ change in young children with developmental delays, as initial diagnosis may help differentiate between potential IQ gains and mental retardation.

The Flynn effect for fluid IQ may not generalize to all ages or ability levels: a population-based study of 10,000 US adolescents.

The Flynn Effect for fluid IQ may not apply to all ages or ability levels, with lower ability levels experiencing worsening IQ over time.

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