Deterioration of frontal lobe function in normal aging: Influences of fluid intelligence versus perceptual speed

A group of young participants were compared with 2 groups of older particip ants (young-old, 65-74 years and old-old, 75 years or over) on a range of f rontal lobe tasks. They were also assessed on the Digit Symbol Substitution Test (DSST), a test of digit cancellation (DC), the AH4 test of fluid inte lligence, and the National Adult Reading Test (NART)-a measure of crystaliz ed intelligence. Reliable age differences on all frontal measures except wo rd fluency (FAS) were found. However, age effects were radically attenuated when either DSST speed or Alice Helm 4 (AH4) performance was used as a cov ariate. In contrast, DC and NART attenuated age-related variance to a much lesser degree. The authors conclude that a large proportion of age-related variance on measures of frontal lobe function may be attributed to a more g eneral factor characterized jointly by DSST and AH4 performance.