Limited generalization with varied, as compared to specific, practice in short-term motor learning

The schema theory of learning predicts that varied training in motor learning should give rise to better transfer than specific training. For example, throwing beanbags during practice to targets 5 and 9 ft away should better generalize to targets 7 and 11 ft away, as compared to only throwing to a target 7 ft away. In this study, we tested this prediction in a throwing task, when the pretest, practice, and posttest were all completed within an hour. Participants in the varied group practiced throwing at 5 and 9 ft targets, while participants in the specific group practiced throwing at 7 ft only. All participants reliably reduced errors from pretest to posttest. The varied group never outperformed the specific group at the 7 ft target (the trained target for the specific group). They did not reliably outperform the specific group at 11 ft, either. The numerically better performance at 11 ft by the varied group was due, as it turned out in a subsequent experiment, to the fact that 11 ft was closer to 9 ft (one of the two training targets for the varied group) than to 7 ft (the training target for the specific group). We conclude that varied training played a very limited role in short-term motor learning.