Age and Verbal Fluency: The Mediating Effect of Speed of Processing

Abstract

Background and Purpose

Cognitive decline is a function of normal aging; however, the effect of age on various domains is differential. This study examined the effect of age on verbal fluency and showed how speed of processing modifies fluency performance in healthy older adults compared to younger individuals.

Methods

Three age groups, 62 young (17–40 years), 30 middle-aged (41–59 years), and 38 older adults (60–78 years), were studied using the Controlled Oral Word Association Test, National Adult Reading Test, and speed-of-processing composite score. The study examined the effect of age on fluency before and after controlling for processing speed and intelligence quotient.

Results

The young group performed better than the older group on category fluency as measured by animal category (p < .001) and on processing speed composite score (p < .001). However, the older group performed better than the young group on the National Adult Reading Test (p < .05) and on letter fluency after controlling for the decline in processing speed (p < .05). Processing speed had a significant effect on both category and letter fluency (p < .01) in older adults.

Conclusions

This study suggests that aging adversely affects some but not all cognitive domains and that age-related decline in processing speed contributes to age-related changes in fluency.