The Journals of Gerontology Series B: Psychological Sciences and Social Sciences 58:P187-P194 (2003)
© 2003 The Gerontological Society of America
Age-Related Slowing of Digit Symbol Substitution Revisited: What Do Longitudinal Age Changes Reflect?
Stuart W. S. MacDonald1,,
David F. Hultsch1,
Esther Strauss1 and
Roger A. Dixon1,2
1 Department of Psychology, University of Victoria, British Columbia, Canada.
2 Department of Psychology, University of Alberta, Edmonton, Canada.
Address correspondence to Stuart W. S. MacDonald, Stockholm Gerontology Research Center, Olivecronas väg 4, Box 6401, S-113 82 Stockholm, Sweden. E-mail: [email protected]. Address correspondence regarding the Victoria Longitudinal Study to Roger A. Dixon at rdixon{at}ualberta.ca.
A previous investigation reported that cross-sectional age differences in Digit Symbol Substitution (DSS) test performance reflect declines in perceptual processing speed. Support for the tenability of the processing speed hypothesis requires examining whether longitudinal age-related change in DSS performance is largely mediated by changes in speed. The present study used data from the Victoria Longitudinal Study to examine patterns and predictors of longitudinal change in DSS for 512 older adults (Mage = 68.37 years, SD = 7.43). On the basis of multilevel modeling, baseline DSS performance was poorer for older participants and men, with longitudinal declines more pronounced with increasing age and decreasing speed. In contrast to the present cross-sectional findings, statistical control of change trajectories in perceptual speed using the same data did not substantially attenuate age changes. These discrepancies suggest different sources of variance may underlie cross-sectional age differences and longitudinal age changes for DSS.
Copyright © 2003 by The Gerontological Society of America.
