Does age affect iq
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The Impact of Age on IQ: A Comprehensive Analysis
Age-Related Decline in Cognitive Abilities
Fluid and Crystallized Intelligence
Research consistently shows that age affects different types of intelligence in distinct ways. Fluid intelligence, which involves problem-solving and reasoning abilities, tends to decline with age. This decline is often mediated by physical health, particularly diseases of the circulatory and nervous systems. On the other hand, crystallized intelligence, which includes vocabulary and general knowledge, remains relatively stable or declines much more slowly .
Subtest Performance Variations
Studies using the Wechsler Abbreviated Scale of Intelligence-Second Edition (WASI-II) reveal that specific subtests are differently affected by age. Vocabulary and Similarities subtests show minimal variation with age, while Block Design and Matrix Reasoning subtests exhibit significant declines as individuals grow older. This pattern aligns with the theory that crystallized intelligence is more resistant to aging compared to fluid intelligence.
The Role of IQ in Aging
IQ and Cognitive Performance
Higher IQ levels are associated with better cognitive performance across various tasks, regardless of age. For instance, in two-choice tasks involving numerosity discrimination, recognition memory, and lexical decision, IQ had a significant impact on the quality of evidence obtained from stimuli, whereas age did not. Similarly, in memory tasks, higher IQ correlated with better performance in item and associative recognition, although the oldest participants showed some decline.
The Wilson Effect
The heritability of IQ increases with age, a phenomenon known as the Wilson Effect. Studies indicate that the heritability of IQ reaches an asymptote of about 0.80 by the age of 18-20 and remains at that level into adulthood. Concurrently, the influence of shared environmental factors decreases significantly. This suggests that genetic factors play a more substantial role in determining IQ as individuals age.
Early Life IQ and Later Outcomes
Longitudinal Studies
Longitudinal studies have shown that higher IQ in adolescence is linked to better outcomes in later life, including a younger subjective age and lower mortality risk. For example, individuals with higher IQs in adolescence tend to feel younger in old age, a relationship mediated by higher openness and other personality traits. Additionally, higher early-life IQ is associated with lower mortality rates in middle and late adulthood, suggesting that cognitive abilities in youth have long-term health implications.
Socioeconomic Status and Health
Early-life IQ also interacts with socioeconomic status (SES) to influence health outcomes in old age. Higher IQ can buffer the adverse effects of low SES on physical and mental health, indicating that cognitive abilities can mitigate some of the negative impacts of socioeconomic disadvantages.
Conclusion
In summary, age does affect IQ, but the impact varies depending on the type of intelligence and individual health factors. Fluid intelligence declines with age, largely mediated by physical health, while crystallized intelligence remains more stable. Higher IQ levels are associated with better cognitive performance and health outcomes across the lifespan. The heritability of IQ increases with age, emphasizing the growing importance of genetic factors. Early-life IQ has lasting effects, influencing subjective age, mortality risk, and the ability to cope with socioeconomic challenges in later life.
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