Pointing Versus Grasping in Young and Older Adults

Abstract

This experiment examined age-related changes in pointing and grasping performance. Based on previous studies, an increase in movement time and the proportion of time in deceleration was expected for both pointing and reaching and grasping tasks (Carnahan, Goodale, & Marteniuk, 1993; Goggin & Stelmach, 1990; Marteniuk, MacKenzie, Jeannerod, Athenes, & Dugas, 1987; Roy, Winchester, Weir, & Black, 1993). Six young and older participants pointed to or grasped 2 disks (2.5 and 7.5 cm in diameter) over 2 amplitudes (15 and 30 cm). Analyses revealed that both age groups were able to scale grasp size to object size, and both showed the predicted task effects on peak velocity (increased with object size and movement amplitude) and time in deceleration (decreased with object size and increased with movement amplitude). However, the older participants in general moved more slowly and had longer acceleration and deceleration times. Also, they were less proficient at modulating peak velocity with movement amplitude and movement goal. These findings suggest that aging does not affect the basic mechanisms underlying movement control and task demands. Rather, aging appears to affect the degree to which these demands impact motor performance.