Types of iconicity and combinatorial strategies distinguish semantic categories in silent gesture across cultures

In this study we explore whether different types of iconic gestures (i.e., acting, drawing, representing) and their combinations are used systematically to distinguish between different semantic categories in production and comprehension. In Study 1, we elicited silent gestures from Mexican and Dutch participants to represent concepts from three semantic categories: actions, manipulable objects, and non-manipulable objects. Both groups favoured the acting strategy to represent actions and manipulable objects; while non-manipulable objects were represented through the drawing strategy. Actions elicited primarily single gestures whereas objects elicited combinations of different types of iconic gestures as well as pointing. In Study 2, a different group of participants were shown gestures from Study 1 and were asked to guess their meaning. Single-gesture depictions for actions were more accurately guessed than for objects. Objects represented through two-gesture combinations (e.g., acting + drawing) were more accurately guessed than objects represented with a single gesture. We suggest iconicity is exploited to make direct links with a referent, but when it lends itself to ambiguity, individuals resort to combinatorial structures to clarify the intended referent. Iconicity and the need to communicate a clear signal shape the structure of silent gestures and this in turn supports comprehension.