The generalization of perceptual-motor intra-individual variability in young and old adults.

We examined the generalizability of intra-individual perceptual-motor variability in young and old adults. Participants completed four motor tasks that all required the maintenance of a steady state: finger tremor, and single-digit, two-digit, and three-digit isometric force production. Older adults had a greater amount of variability and an increased time and frequency structure of variability, except in the tremor task. There was a moderate association between the magnitudes of variability across tasks in the oldest age group, but the structural measures of variability were more highly related across tasks and the strength of this relationship increased with age. These findings support the hypothesis that older adults are less able than younger adults to adapt the structure of their perceptual-motor variability to task demands.