Enforcing a high success percentage interferes with reward-based motor learning

Humans can adapt their movements based on binary reward feedback about success and failure. To engage in such ‘reward-based’ motor learning, the learner must encounter at least some failures, but it is unclear what percentage of failures is optimal. For learning, we hypothesize that a success percentage of 50% is optimal, as it provides the most information. For motivation, in contrast, we hypothesize that a success percentage of 80% is optimal, since too many failures can reduce motivation. In this study, we simultaneously test the hypotheses on learning and motivation in participants of a wide age range (7 to 58 years) who performed a brief circle-drawing task. The participant’s goal in this task was to double the size of the baseline circles drawn with the unseen hand. We assigned participants to a reward scheme that targets either 50% success (moderate success group) or 80% success (high success group). In line with our hypothesis on learning, the results show more motor learning in the moderate success group compared to the high success group. In contrast to our hypothesis on motivation, motivation was not higher in the high success group.