Generalization of Motor Learning in Psychological Space.

The capacity to generate adaptive movements largely depends on how we generalize what we have previously learned to novel situations. The generalization of adapted movements has typically been framed as a consequence of neural tuning functions that overlap for similar movement kinematics-what might be considered bottom-up generalization. However, as is true in many domains of human behavior, generalization can also be framed as the result of goal-directed, deliberate decisions about how to act (top-down generalization). Here, we attempt to broaden the scope of theories about motor generalization, hypothesizing that part of the typical motor generalization function is associated with goal-directed decisions concerning the subjective similarity of different movement contexts. We tested this proposal by having participants make explicit similarity ratings over both traditional kinematic contextual dimensions (movement direction) and more abstract contextual dimensions (target shape) and perform a visuomotor adaptation generalization task where trials varied over those dimensions. Across five experiments, we measured the relationship between subjective similarity ratings and motor generalization. In some cases, this link was rather strong, though it was determined by the inferred goals of participants (e.g., task relevance, explicit instruction, etc.). These results support a broadening of current frameworks to explain the generalization of motor behaviors and support a more careful deployment of goal- and task-relevant instructions in generalization studies.