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 primary 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 two age groups were similar in the strategies they used to compose single movements from a variety of submovements. However, when performing sequences of movements containing varied target distances, older adults exhibited a repetition effect whereas younger adults exhibited a contrast effect. Older adults may plan movements individually, whereas younger adults plan sequences.