Background: Fluid intelligence declines with advancing age, starting in early adulthood. Within-subject declines in fluid intelligence are highly correlated with contemporaneous declines in the ability to live and function independently.

Why does fluid intelligence decline with age?

Age-related declines in fluid intelligence, speed of processing, and frontal function were observed. ... These findings suggest that the age-related decline in fluid intelligence is due to general slowing and frontal decline, as well as other unidentified factors.

How does fluid intelligence change with age?

Fluid and crystallized intelligence tend to change throughout life, with certain mental abilities peaking at different points. ... Crystallized intelligence continues to grow throughout adulthood. Many aspects of fluid intelligence peak in adolescence and begin to decline progressively beginning around age 30 or 40.