Proceedings of the Annual Meeting of the Cognitive Science Society

Why do people gesture when they speak? On one proposal, people gesture because they speak: Gestures reflect speechproduction processes. Alternatively, people gesture because they think: Gestures reflect non-linguistic thinking processes.If gestures during speech grow out of thinking, not simply speaking, then co-speech gestures should look similar to thegestures that are produced during silent thinking without speech. Here, we looked at spontaneous gestures during mentalabacus, a non-linguistic technique for rapid arithmetic operations via imagining moving beads on an abacus. We comparedhow expert mental abacus users spontaneously gesture during silent thinking (no-speech) and during explaining how theysolved the arithmetic problems (speech). In both the speech and the no-speech condition, gestures reflected operations ona mental abacus in the same way (e.g. depicting the trajectory of beads). These results suggest that at least some co-speechgestures grow out of thinking processes that are independent of speaking.