Cognitive aging research reveals a complex picture: while some cognitive abilities decline with age, others are remarkably preserved. Fluid abilities — processing speed, working memory, episodic memory, and executive function — show significant age-related declines beginning in middle adulthood and accelerating in later life. Crystallized abilities — vocabulary, general knowledge, and expertise-based skills — are maintained or even improve into the 60s and 70s. This dissociation between declining fluid and preserved crystallized abilities is one of the most robust findings in cognitive aging research.
Processing Speed
Timothy Salthouse proposed that slowed processing speed is the fundamental mechanism underlying age-related cognitive decline. Processing speed, measured by simple tasks like symbol comparison, slows continuously from young adulthood onward, and this slowing statistically accounts for much of the age-related variance in more complex cognitive tasks like reasoning and memory. The neural basis includes white matter deterioration and reduced dopamine levels in the prefrontal cortex.
There is enormous variability in cognitive aging — some 80-year-olds perform at the level of 50-year-olds. Factors associated with better cognitive aging include physical exercise (particularly aerobic exercise), cognitive engagement (education, intellectually stimulating activities), social engagement, good cardiovascular health, and absence of depression. While "brain training" programs have been widely marketed, evidence for transfer from training to real-world cognitive improvement remains limited.