Evolution of Pantomime in Dyadic Interaction. A Motion Capture Study

Due to the robust iconic potential of visual representations, gestural, and pantomimic hypotheses of language origins are well suited to provide solutions to the bootstrapping problem: how to begin communicating when no signs yet exist. However, the one-off, unstandardised nature of improvised gestures and pantomimes implies substantial costs in terms of time, cognitive effort, and replication fidelity. Hence, gestural and pantomimic hypotheses point to pressures for efficiency that would streamline the originally unwieldy embodied representations into forms that are progressively reduced, take up less space and time, and are less costly to produce. Pantomimic theories of language origins are especially interesting from this perspective since they put a spotlight on the transition from whole-body pantomimes into manual-only gestures. These processes, which we refer to as reduction and manual specialisation, have been virtually unaddressed with direct measurement. We report an experiment in which participants used whole-body pantomimes to communicate a set of transitive actions. Motion-capture technology was used to measure the kinematic characteristics of participants’ movements. In line with the prediction of pantomimic hypotheses of language origins, we saw an increase in the ratio of hand and arm movements versus the movements of other bodily articulators, suggesting a gradual transition from more costly whole-body pantomime to more economic manual gesture. We also found that with successive rounds of interaction, the volume of participants’ movements and the path travelled by their bodily articulators decreased.