The role of motor context in the beneficial effects of hand gesture on memory.

Viewing co-speech hand gestures with spoken phrases enhances memory for phrases, as compared to when the phrases are presented without gesture. Prior work investigating the mechanism underlying the effect of gesture on memory has implicated engagement of the motor system; when the hands are engaged in an unrelated motor task when viewing gesture, the beneficial effect of gesture is absent. However, one alternative interpretation of these findings is that the beneficial effect of gesture disappears due to mismatched contexts at encoding and retrieval: The hands are engaged during either encoding or retrieval, but not during both stages. Here we examined whether matching the motor context at encoding and retrieval plays a role in the beneficial effect of gesture on memory during a phrase recall task. Participants were presented with phrases that were viewed with and without gesture. Participants were assigned to one of four conditions that determined whether they would complete an unrelated motor task at (1) encoding only, (2) retrieval only, (3) both encoding and retrieval, or (4) neither. During stages in which they were not completing a motor task, participants' hands were in their laps. We found that gesture enhanced memory for phrases both when participants engaged in an unrelated motor task at encoding and retrieval and when they did not complete the motor task during either stage. Furthermore, phrases observed with gesture were more likely to be paraphrased than to be recalled literally. Together, these findings demonstrate that gesture can enhance memory even when the motor system is engaged in another task, as long as that same task is performed at retrieval.