Differential decline of verbal and visuospatial processing speed across the adult life span

The present study compared the age-related decline in verbal and visuospatial processing speed in 131 participants aged 18 to 90 years. Participants performed four verbal and four visuospatial tasks. Age differences in processing speed were compared at the group and individual levels. For the group-level analyses, participants were divided into a young adult group and six older groups subdivided by decade. The mean verbal and visuospatial response times (RTs) for each group were regressed on the corresponding RTs of the young adult group. The slope of the visuospatial regression was greater than that for the verbal regression at all ages, and the difference between the visuospatial and verbal slopes increased with each decade. For the individual-level analyses, a verbal and a visuospatial processing-time coefficient (Hale and Jansen, 1994) was obtained for each individual, and these values were then regressed on age. Verbal processing time increased linearly by approximately 50% while visuospatial processing time increased exponentially by approximately 500% from 18 to 90 years. Taken together, the results at both the group and the individual level demonstrate that aging affects visuospatial processing to a much greater extent than verbal processing.