Does intelligence decline with age
Pro Research Analysisby 
Searched over 200M research papers
Consensus Meter
Does Intelligence Decline with Age?
Fluid Intelligence Decline in Adulthood
Research consistently shows that fluid intelligence (Gf), which involves the capacity to solve novel problems, declines with age. Studies indicate a decline of approximately 3 to 7 IQ points per decade between the ages of 30 and 60. This decline is primarily attributed to deficits in processes such as organizing information, maintaining attention, and working memory.
Cognitive Decline Before and After Age 65
Cognitive decline is a well-documented phenomenon, particularly after age 65. However, research from the UK Biobank suggests that declines in cognitive abilities before age 65 are relatively small. Performance on various cognitive tests, including fluid intelligence, reaction time, and memory, shows a more pronounced decline after age 65.
Longitudinal Studies on Cognitive Decline
Longitudinal studies, such as the Berlin Aging Study, reveal that perceptual speed, memory, and fluency decline with age, while knowledge remains stable until around age 90, after which it also begins to decline. These findings suggest that different cognitive abilities decline at different rates, with some remaining stable for longer periods.
Shared Variation in Cognitive Decline
A meta-analysis of multiple datasets indicates that about 60% of the variation in cognitive changes is shared across different cognitive abilities, and this shared variation increases with age. This suggests a general factor of cognitive aging that becomes more pronounced as individuals grow older.
Neural Correlates of Cognitive Decline
Age-related cognitive declines are often linked to changes in the brain, particularly in the prefrontal cortex. Research shows that fluid intelligence and multitasking abilities are mediated by different neural subsystems, which are differentially affected by aging. This indicates that cognitive aging is a multifaceted process involving various neural changes.
Impact of Intelligence on Cognitive Decline and Dementia Risk
Higher intelligence in childhood does not appear to significantly protect against cognitive decline in old age. However, individuals with higher IQs may experience a delayed onset of terminal decline, although their rate of decline may be steeper once it begins. This supports the cognitive reserve hypothesis, which posits that higher cognitive reserve can delay the onset of decline but not prevent it entirely.
Socioeconomic Factors and Cognitive Aging
Socioeconomic conditions in childhood have a lasting impact on cognitive functioning in later life. Individuals from more affluent backgrounds tend to have higher levels of fluid intelligence in old age but may experience a faster rate of decline. This suggests that while early-life advantages can boost cognitive reserve, they do not necessarily protect against the eventual decline.
Conclusion
In summary, intelligence does decline with age, particularly fluid intelligence. This decline is influenced by various factors, including neural changes, socioeconomic conditions, and individual differences in cognitive reserve. While some cognitive abilities remain stable longer than others, the general trend is a decline in cognitive performance as individuals age.
Sources and full results
Most relevant research papers on this topic