Does iq drop with age

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Does IQ Drop with Age?

Age-Related Decline in IQ: General Trends

Research consistently shows that IQ tends to decline with age, but the pattern of this decline varies between different types of intelligence. Performance IQ, which involves problem-solving and processing speed, tends to decline earlier and more rapidly compared to verbal IQ, which involves language and knowledge-based skills. This trend is observed in both cross-sectional and longitudinal studies.

Verbal vs. Performance IQ Decline

Studies indicate that verbal abilities decline more slowly and later in life compared to performance abilities. For instance, the Wechsler Abbreviated Scale of Intelligence-Second Edition (WASI-II) shows that vocabulary and similarities subtests, which are verbal tasks, are more resistant to aging. In contrast, block design and matrix reasoning, which are performance tasks, show substantial declines starting from middle age. This pattern is consistent with the theory of crystallized and fluid intelligence, where crystallized intelligence (verbal skills) remains stable longer than fluid intelligence (performance skills).

Influence of Baseline IQ and Cognitive Reserve

Higher baseline IQ appears to provide a buffer against age-related cognitive decline, a concept known as the cognitive reserve hypothesis. Individuals with higher IQs tend to experience a later onset of terminal decline in cognitive abilities, although once the decline begins, it tends to be steeper. This suggests that while higher IQ can delay the onset of cognitive decline, it does not prevent it entirely.

Impact of Physical Health on IQ Decline

Physical health significantly mediates the effect of age on fluid intelligence. Diseases of the circulatory and nervous systems are major contributors to the decline in fluid IQ, which involves problem-solving and reasoning abilities. Improving physical health can potentially mitigate some of the age-related declines in fluid intelligence.

Longitudinal Studies and Brain Aging

Longitudinal studies examining brain aging and psychometric intelligence reveal that while there is a significant decline in brain volumes (e.g., grey matter and white matter) with age, these changes do not necessarily correlate with a simultaneous decline in IQ measures. This suggests that some individuals may maintain their cognitive abilities despite neuroanatomical changes.

Practice Effects and Cognitive Trajectories

Repeated testing can lead to practice effects, where individuals show initial improvements in test scores due to familiarity with the test rather than actual cognitive improvements. However, over time, the decline in fluid intelligence becomes evident, with an average annual decrease observed in studies using Raven's Progressive Matrices.

Conclusion

In summary, IQ does decline with age, but the extent and pattern of this decline vary between different types of intelligence. Verbal abilities tend to be more resilient compared to performance abilities. Higher baseline IQ and better physical health can delay the onset of cognitive decline, although they do not prevent it entirely. Understanding these patterns can help in developing strategies to maintain cognitive health in aging populations.