In July 2024, President Joe Biden withdrew from his campaign for reelection to the US Presidency largely due to concerns over his apparent decline in cognitive abilities. But what do we actually know about how our cognitive abilities decline as we age? Breit and colleagues decided to examine the stability of eleven major cognitive abilities over the lifespan from preschool age to late adulthood (80 and older). They analyzed the results of 205 studies testing over 87 thousand individuals at various points in their lives, using a test-retest procedure. As we might expect, they found that cognitive abilities grow rapidly during the first 20 years of life and then become remarkably stable for the remainder of the lifespan. Nevertheless, significant individual differences in cognitive stability appeared in later adulthood with some older individuals (55 to 90 years of age) showing greater declines in cognitive ability than others in the same age group, with the biggest individual differences in cognitive stability appearing around age 70.
Fluid versus Crystallized Cognitive Abilities
One particularly important finding was that reasoning abilities that require cognitive effort (fluid reasoning) were more likely than knowledge-based abilities (crystallized intelligence) to decline as people aged. The authors explained this somewhat counter-intuitive result as follows:
This theory proposes that during cognitive development, fluid (or effortful processing–based) abilities are invested in the acquisition of crystallized (or knowledge-based) abilities. As the result of years of cumulative investment, these crystallized abilities are acquired and automated, such that they are better maintained even as currently available processing power wanes with aging…or varies from day to day. [p.424]
President Joe Biden, prior to his decision to end his reelection campaign, similarly argued that while he was indeed aging, he had accumulated vast wisdom and political know-how; that is, crystallized intelligence. He was probably right. Voters’ concern of course was that a President also needs to be able to reason through new problems that inevitably arise from time-to-time, if not daily.
Continue reading “How Do Our Cognitive Abilities Change As We Age?”
Dr Martin Fracker 