One theory of normal cognitive aging asserts that
decreases in simple processing speed mediate the age-related
decline of fluid intelligence. Another possibility is that
age-related atrophic changes in frontal brain structures
undermine the functioning of executive abilities, thereby
producing the same decline. In this study, we used principal
components analysis to derive a measure of fluid–spatial
intelligence in 197 normal adults between 20 and 92 years
of age. Measures of perceptual comparison speed, working
memory, and executive ability, as well as regional brain
volumes based on high resolution magnetic resonance imaging
were obtained from a subsample of 112 participants. We
then conducted a series of hierarchical multiple regression
analyses to test whether (1) the processing speed theory,
(2) frontal–executive theory, or (3) some combination
of these best accounted for age-related variation in fluid
intelligence. The results showed that perceptual comparison
speed, executive ability, and frontal lobe volume each
made significant contributions to a regression equation
that explained 57% of the variance in fluid intelligence.
These findings suggest that both the processing speed and
frontal–executive theory of cognitive aging are partially
correct and complement one another. (JINS, 2000,
6, 52–61.)
Perceptual Comparison of Procedural and Data-Driven Eye Motion Jitter