Sensori-motor strategic variations and sequential effects in young and older adults performing a Fitts' task.

The present study aimed at investigating age-related changes in strategic variations and sequential effects in discrete Fitts' aiming task. Three sequential effects were investigated, namely trial sequential difficulty effects (TSDE), strategy sequential difficulty effects (SSDE), and strategy repetition effects (SRE). After generalizing previously observed aging effects on strategic variations, our results showed that movement times were longer when performed after harder ID level than when following easier ID level (TSDE). We also observed SSDE, such that is movement times were longer when participants executed a strategy of intermediate difficulty (i.e., the progressive-deceleration strategy) after having used a more difficult strategy (i.e., the undershoot strategy) on the previous trial than after an easier strategy (i.e., the one-shot strategy). These sequential difficulty effects related to both difficulty and strategy were similar in young and older adults. In addition, we found that across two successive trials, participants tended to repeat the one-shot strategy the most often and the undershoot strategy the least often, with repetition rates of the progressive-deceleration strategy being in-between (SRE). Finally, age-related differences in strategy repetition effects varied with strategies (e.g., they were largest for the one-shot strategy). These findings have important implications for deciphering processes responsible for sequential effects in sensori-motor tasks as well as in cognitive tasks in general, and for our understanding of processes underlying sensori-motor performance in young and older adults.