Final answer:
Research indicates that processing speed declines more significantly than memory in late adulthood, a result of changes in brain function due to aging. Mental and physical activities can help mitigate these declines.
Step-by-step explanation:
Longitudinal follow-ups of individuals varying widely in age confirm that processing speed shows greater decrements than memory in late life. This decline in processing speed over memory happens due to age-related changes in the brain's structure and functioning. For example, degeneration of corticostriatal connections can lead to slower processing speeds in older adults. While both crystallized and fluid intelligence are affected by aging, it is the fluid intelligence, which encompasses processing abilities and reasoning, that tends to decline more sharply in late adulthood. Fortunately, engaging in mental and physical activities can help delay cognitive decline and reduce the incidence of dementia and other cognitive impairments.