Analysing your IQ
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18-65 years · Average IQ: 100 (age-normalized)
Adult IQ scores reflect the interplay between fluid intelligence (which peaks in the mid-20s and gradually declines) and crystallized intelligence (which continues to grow through middle age). The average adult IQ is 100 by definition. Most cognitive abilities remain stable through the 60s, with only processing speed showing significant age-related decline before age 65.
Fluid intelligence peaks between ages 20-25 and gradually declines at approximately 1-2 points per decade
Crystallized intelligence (vocabulary, general knowledge) continues to increase until ages 60-70
Overall IQ remains relatively stable from 25-65 as crystallized gains offset fluid losses
Processing speed shows the earliest and most significant age-related decline, beginning in the late 20s
Working memory capacity peaks in the early 20s and declines modestly through middle age
Education, occupational complexity, and continued learning can buffer age-related cognitive decline
Physical exercise, particularly aerobic exercise, is associated with preserved cognitive function in middle age
Adulthood illustrates the classic divergence between fluid and crystallized intelligence. Fluid intelligence (novel problem-solving, abstract reasoning) peaks in the mid-20s, then declines gradually. Crystallized intelligence (accumulated knowledge, vocabulary, expertise) continues growing well into the 60s. This is why experienced professionals often outperform younger colleagues despite slower processing speed.
The WAIS-IV is the standard adult intelligence test. Online IQ tests can provide rough estimates but lack clinical standardization. Factors affecting adult IQ scores include: sleep quality, stress levels, medication, alcohol consumption, and testing conditions. A comprehensive assessment takes 60-90 minutes and should be administered by a licensed psychologist.
Fluid intelligence peaks between ages 20-25. Crystallized intelligence peaks between ages 60-70. Overall composite IQ scores are relatively stable from 25-65, as the two components offset each other. The "peak" depends on which cognitive ability you measure.
Fluid intelligence (processing speed, working memory, novel problem-solving) begins declining gradually after the mid-20s. However, crystallized intelligence (vocabulary, knowledge, wisdom) continues to grow. Overall IQ remains relatively stable through middle age. Significant decline typically occurs only after age 70-75.
While the genetic component of IQ becomes stronger in adulthood (heritability reaches 60-80%), lifestyle factors can still influence scores. Regular exercise, quality sleep, continued learning, and cognitive stimulation are associated with maintained or modestly improved cognitive function. Dramatic increases (>10 points) are rare in adulthood.
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