Probing the mental representation of gesture: Is handwaving spatial?

What type of mental representation underlies the gestures that accompany speech? We used a dual-task paradigm to compare the demands gesturing makes on visuospatial and verbal working memories. Participants in one group remembered a string of letters (verbal working memory group) and those in a second group remembered a visual grid pattern (visuospatial working memory group) while explaining math problems. If gesture production is mediated by visuospatial representation, gesturing should interfere more with performance on the concurrent visuospatial task than the concurrent verbal task. We found, however, that participants in both groups remembered significantly more items when they gestured than when they did not gesture. Moreover, the number of items remembered depended on the meaning conveyed by gesture. When gesture conveyed the same propositional information as speech, participants remembered more items than when it conveyed different information. Thus, in contrast to simple handwaving, the demands that gesture makes on working memory appear to be propositional rather than visuospatial.