This study investigates the communicative factor that has an effect on the production of gestures during speech. 24 university students explained the definition of nouns referred to concrete objects and abstract concepts to an imaginary child who didn't know those words. In one condition, they were instructed that their explanations would be video-recorded, and in the other condition, they were instructed that their explanations would be audio-recorded. Their explanations in both conditions were video-recorded and analyzed. The analysis shows that subjects produced more gestures in the video-recorded condition than audio-recorded condition. When those gestures were classified into two groups according to their viewpoints, gestures from the objective viewpoint were produced more frequently than those from the subjective viewpoint in the video-recorded condition. These results suggest the strong effect of the communicative factor on the process of gesture production. Gestures are not mere externalization of mental representation, but they are modified according to demands of communicative interaction between the speaker and the listener.
