On the cognitive processes underlying contextual interference: Contributions of practice schedule, task similarity and amount of practice.

This experiment was designed to assess the combined influence of practice schedule (blocked or random), task similarity (similar or dissimilar), and amount of practice on motor learning. Participants were required to perform three movement times (200, 350, and 500ms) in a blocked or random schedule while pointing towards the target located in the front direction in the similar condition, or towards three targets (left, front, and right) in the dissimilar condition. In each condition, participants completed 99 or 297 acquisition trials before a delayed retention test similar for all participants. Results indicated a contextual interference (CI) effect due to the schedule of practice following 297 trials for similar task variations: blocked schedule tended to produce better performance early in practice; random schedule enhanced learning for a larger amount of practice. However, when participants experienced dissimilar task variations, no blocked-random difference was found whatever the amount of practice. This suggests that task similarity is a learning variable that modulates the CI effect. Our findings argue for the evidence that the intertask processing evoked by random schedule is not sufficient to improve learning and that there may be a ceiling effect on retention performance due to the extent of additional intertask processing.