Gesturing during disfluent speech: A pragmatic account.

People are more likely to gesture when their speech is disfluent. Why? According to an influential proposal, speakers gesture when they are disfluent because gesturing helps them to produce speech. Here, we test an alternative proposal: People may gesture when their speech is disfluent because gestures serve as a pragmatic signal, telling the listener that the speaker is having problems with speaking. To distinguish between these proposals, we tested the relationship between gestures and speech disfluencies when listeners could see speakers' gestures and when they were prevented from seeing their gestures. If gesturing helps speakers to produce words, then the relationship between gesture and disfluency should persist regardless of whether gestures can be seen. Alternatively, if gestures during disfluent speech are pragmatically motivated, then the tendency to gesture more when speech is disfluent should disappear when the speaker's gestures are invisible to the listener. Results showed that speakers were more likely to gesture when their speech was disfluent, but only when the listener could see their gestures and not when the listener was prevented from seeing them, supporting a pragmatic account of the relationship between gestures and disfluencies. People tend to gesture more when speaking is difficult, not because gesturing facilitates speech production, but rather because gestures comment on the speaker's difficulty presenting an utterance to the listener.