QUANTIFYING THE PERFORMANCE LIMITATIONS OF OLDER AND YOUNGER ADULTS IN A TARGET ACQUISITION TASK

In a stationary target acquisition task, both 65-year-old and 20-year- old adults exhibited a negatively accelerated curvilinear relationship between the spatial variability of submovement endpoints and average submovement velocity. For high velocities, the variability was greater for the older adults. This elevated motor noise is considered a prima ry cause of their slower performance. Both age groups also exhibited a linear relationship between submovement duration and the logarithm of submovement relative accuracy A stochastic model indicates that the t wo age groups were similar in the strategies they used to compose sing le movements from a variety of submovements. However, when performing sequences of movements containing varied target distances, older adult s exhibited a repetition effect whereas younger adults exhibited a con trast effect. Older adults may plan movements individually, whereas yo unger adults plan sequences.