How much does your iq increase with age
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The Relationship Between IQ and Age: A Comprehensive Analysis
Heritability of IQ Increases with Age
Research has shown that the heritability of IQ, which refers to the proportion of variance in IQ attributable to genetic factors, increases as individuals age. This phenomenon, known as the Wilson Effect, indicates that genetic influences on IQ become more pronounced over time. Studies involving twins and adopted children reveal that the heritability of IQ reaches approximately 0.80 by the age of 18-20 and remains at that level into adulthood. Concurrently, the influence of shared environmental factors diminishes, stabilizing at around 0.10 by the same age range1.
The Flynn Effect and Age-Related Variations
The Flynn Effect, which describes generational increases in IQ scores, does not uniformly apply across all ages and ability levels. A large-scale study of American adolescents aged 13-18 found significant variability in IQ changes over time. For instance, while 13-year-olds exhibited an average IQ increase of 2.3 points per decade, 18-year-olds experienced a decrease of 1.6 points per decade. Additionally, individuals with lower IQs (<70) saw a decline of 4.9 points, whereas those with higher IQs (>130) saw an increase of 3.5 points. These findings suggest that the Flynn Effect is not a one-size-fits-all phenomenon and that age and ability level significantly influence IQ trends2.
IQ Development in Children with Autism
In children with autism, IQ tends to increase with age, likely due to both genuine cognitive development and the later diagnosis of higher-functioning children. Early in life, many children with autism show normal motor development but delayed speech. As they grow older, the gap between verbal and non-verbal IQ narrows, particularly by school age. Visual reasoning skills often surpass other cognitive abilities, while graphomotor skills lag behind. These patterns highlight the complex interplay between age, IQ, and specific cognitive abilities in children with autism3.
Stability of IQ in Phenylketonuria Patients
For individuals with phenylketonuria (PKU), a metabolic disorder, IQ development stabilizes after the age of 10, regardless of dietary relaxation. However, higher blood phenylalanine levels during early childhood are associated with lower IQ scores. Children with well-managed phenylalanine levels tend to have near-normal IQs. This stability in IQ post-age 10 underscores the importance of early and consistent dietary management in mitigating cognitive deficits associated with PKU4.
Conclusion
The relationship between IQ and age is multifaceted, influenced by genetic factors, environmental conditions, and specific health conditions. While the heritability of IQ increases with age, the Flynn Effect demonstrates that generational IQ changes are not uniform across all ages and ability levels. In special populations, such as children with autism or those with PKU, age-related IQ trends further underscore the complexity of cognitive development. Understanding these dynamics is crucial for developing targeted interventions and support systems to optimize cognitive outcomes across the lifespan.
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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.
Highly CitedThe 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.
Observational StudyAbility Profiles in Children with Autism
Children with autism show a gradual increase in IQ as they age, with verbal IQ lagging behind non-verbal IQ, but by school age, the gap has closed and visual reasoning surpasses IQ for most.
Observational StudyHighly CitedDevelopment of intelligence in early treated phenylketonuria
Early treatment of phenylketonuria (PKU) leads to stable IQ development after 10 years, with children having near normal outcomes.
Meta-AnalysisHighly CitedIQ as Moderator of Terminal Decline in Perceptual and Motor Speed, Spatial, and Verbal Ability: Testing the Cognitive Reserve Hypothesis in a Population-Based Sample Followed From Age 70 Until Death
Higher IQ is associated with a delayed onset of terminal decline in cognitive abilities, such as speed and verbal ability, and a steeper decline rate in those abilities.
Observational StudyChanges in thickness and surface area of the human cortex and their relationship with intelligence.
Higher intelligence is associated with thinner cortexes and faster thinning of the brain, with the cortex continuing to develop and expand intelligence-dependently.
Observational Study
Very Rigorous JournalHighly CitedIntellectual development from early childhood to early adulthood: The impact of early IQ differences on stability and change over time
Higher initial IQ scores maintain advantages throughout the study period, with low-IQ children showing higher stability over time and more likely to attend higher educational tracks.
Observational StudyHighly CitedA 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.
Observational StudyBrain aging and psychometric intelligence: a longitudinal study
Healthy older adults experience age-related neuroanatomical decline, but these changes are not necessarily linked to simultaneous cognitive deterioration.
Observational Study
Rigorous JournalIQ Constancy and Age
IQ consistency and age show a perfect relationship, with correlations increasing with age, but no sex differences in IQ changes were observed.
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