Pointing versus grasping in young and older adults

This experiment examined age-related changes in pointing and grasping perfo rmance. Based on previous studies, an increase in movement time and the pro portion of time in deceleration was expected for both pointing and reaching and grasping tasks (Carnahan, Goodale, & Marteniuk, 1993; Goggin & Stelmac h, 1990; Marteniuk, MacKenzie, Jeannerod, Athenes, & Dugas, 1987; Roy, Winc hester, Weir, & Black, 1993). Six young and older participants pointed to o r 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 decelerati on (decreased with object size and increased with movement amplitude). Howe ver, the older participants in general moved more slowly and had longer acc eleration and deceleration times. Also, they were less proficient at modula ting peak velocity with movement amplitude and movement goal. These finding s suggest that aging does not affect the basic mechanisms underlying moveme nt control and task demands. Rather, aging appears to affect the degree to which these demands impact motor performance.