Speed and memory in WAIS-R-NI Digit Symbol performance among healthy older adults

Although roles have been proposed for both graphomotor speed and learning in the execution of Digit Symbol, few data have been available concerning performance across the adult lifespan on the Symbol Copy, paired associates, or free recall measures derived from Digit Symbol and recommended in the WAIS-R-NI. We report findings on 177 healthy older adults (ages 50-90), providing normative data by age group, education level, and gender. As previously reported, Digit Symbol scores decline steeply with age (r = -.64). Symbol Copy speed declines almost as steeply (r = -.58). Incidental learning, however, declines only modestly (r = -.26 on both measures). Symbol Copy is a far stronger correlate of Digit Symbol (r = .72) than are paired associates or free recall (r = .26 and r = .28, respectively). The 2 incidental learning measures do, however, offer valuable supplementary information as part of a comprehensive individual assessment. When low Digit Symbol scores are produced by slowing on Symbol Copy, further evaluation of perceptual and motor speed and dexterity are indicated. When low incidental learning scores are obtained, further evaluation of memory is warranted. Qualitative analysis of errors (e.g., rotations) made on the incidental learning procedures may also be valuable.