Under load: The effect of verbal and motoric cognitive load on gesture production

It has been hypothesized that speech and gesture work together, with people relying more on gesture when speaking is hard, and relying more on speech when gesturing is hard. Indeed, previous work showed that when speaking is hard, gesture production can reduce cognitive load and thereby help the speech process. However, it is yet unknown what happens in speech and gesture production when gesturing is hard. In the current study, participants described complex tangram figures. Difficulty in either speech or gesture production was manipulated by having speakers do a secondary task which placed them under either verbal or motoric cognitive load. Results showed an increase in representational gesture rate when participants were under motoric load, as compared to the baseline condition, but only a weak effect of verbal load, and no difference between the verbal and motoric load conditions. Based on these findings, we conclude that making speaking hard caused a marginal increase in gesture production, and making gesturing hard actually led to more gestures. In sum, we find no evidence to support a two-way trade-off between speech and gestures. To our knowledge, this is the first study assessing the effects of a secondary motoric task on gesture production.