Does iq depend on age
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The Relationship Between IQ and Age: A Comprehensive Analysis
Heritability of IQ and Age: The Wilson Effect
The heritability of IQ, known as the Wilson Effect, increases with age. Studies involving twins and adoption scenarios have shown that the heritability of IQ reaches an asymptote of about 0.80 between the ages of 18 and 20, maintaining this level into adulthood. Concurrently, the influence of shared environmental factors decreases to approximately 0.10 by the same age range and remains stable thereafter.
Age-Related Changes in IQ Performance
Research examining the effects of aging on IQ performance in various tasks, such as numerosity discrimination and recognition memory, indicates that while performance declines with age, these declines are not significantly different between individuals with low and high IQs. IQ has a substantial impact on the quality of evidence obtained from stimuli or memory, which influences decision-making processes. Additionally, older adults tend to show increased variability in timing tasks, although their average performance remains accurate.
Longitudinal Studies on IQ and Aging
Longitudinal studies using the WAIS-III have explored age-related changes in intellectual abilities across a broad age range (16-89 years). These studies reveal that while there are generational changes in the age-IQ relationship, the patterns of intellectual decline and stability can be interpreted through Horn's theory of fluid and crystallized intelligence. Fluid intelligence tends to decline with age, whereas crystallized intelligence remains relatively stable.
Childhood IQ as a Predictor of Adult Outcomes
Childhood IQ has been shown to predict adult educational and occupational status. By the second grade, the predictive correlations of childhood IQ with adult outcomes approach those of contemporaneous adult IQs, particularly for occupational status . Furthermore, higher childhood IQ is associated with lower mortality rates in later life, suggesting that early cognitive abilities have long-term health implications.
Stability of IQ Across the Lifespan
The Scottish Mental Surveys of 1932 and 1947 provide evidence for the stability of IQ scores from childhood to old age. These surveys also highlight the impact of childhood intelligence on survival and health in old age, with higher childhood IQ being linked to better health outcomes and lower mortality rates.
Subjective Age and IQ
Higher IQ in adolescence is associated with a younger subjective age in later life. This relationship is mediated by factors such as higher openness, suggesting that early cognitive abilities influence how old or young individuals feel as they age.
Differentiation of Cognitive Abilities in Childhood
Age may moderate the effect of IQ on the differentiation of cognitive abilities during childhood. Studies indicate that the relationships among cognitive subtests evolve with age, and this differentiation process appears to be influenced by IQ levels.
Conclusion
In summary, IQ is influenced by age in various ways. The heritability of IQ increases with age, while the impact of shared environmental factors decreases. Performance on IQ-related tasks declines with age, but the extent of this decline is moderated by IQ levels. Childhood IQ is a strong predictor of adult outcomes, including educational attainment, occupational status, and health. The stability of IQ across the lifespan and its influence on subjective age further underscore the complex relationship between IQ and age.
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