The psychological construct of word fluency.

Measures of word fluency have been convincingly linked in the literature to damage in the left prefrontal lobe region. Yet, a reduction in word fluency has also been reported with diffuse, multifocal and nonfrontal lobe damage. Despite the undisputed neuropsychological application of multiple word fluency measures, the psychological construct underlying this measure is not well understood. In a sample of 360 normal adults stratified by age, gender, and level of education, we found that auditory attention and word knowledge were among the most important determinants. With respect to memory, short-term memory was not significantly correlated, but long-term memory was. Despite these three determinants, a large share of the variance of the multiple regression was still not accounted for, which underscores the partial independence of word fluency per se. Thus, we propose a distinction between (1) poor word fluency secondary to deficient verbal attention, word knowledge, and/or verbal long-term memory and (2) impaired word fluency without these three areas concurrently affected. Based on a review of the literature, it seems likely that in the latter condition, the profile is more associated with prefrontal lobe impairment, versus in the former condition, diffuse multifocal or nonfrontal lobe factors can play a role.