What properties of talk are associated with the generation of spontaneous iconic hand gestures?

When people talk, they frequently make movements of their arms and hands, some of which appear connected with the content of the speech and are termed iconic gestures. Critical to our understanding of the relationship between speech and iconic gesture is an analysis of what properties of talk might give rise to these gestures. This paper focuses on two such properties, namely the familiarity and the imageability of the core propositional units that the gestures accompany. The study revealed that imageability had a significant effect overall on the probability of the core propositional unit being accompanied by a gesture, but that familiarity did not. Familiarity did, however, have a significant effect on the probability of a gesture in the case of high imageability units and in the case of units associated with frequent gesture use. Those iconic gestures accompanying core propositional units variously defined by the properties of imageability and familiarity were found to differ in their level of idiosyncrasy, the viewpoint from which they were generated and their overall communicative effect. This research thus uncovered a number of quite distinct relationships between gestures and speech in everyday talk, with important implications for future theories in this area.