It has been hypothesized that the iconic hand gestures that accompany talk communicate important semantic information. This research tests whether some gestures, in the absence of speech, are more communicative than others and considers what properties of gestures might affect their communicative power. Our research found that the communicative power of gestures does vary greatly, and that this is significantly affected by the viewpoint from which a gesture is generated, with character viewpoint gestures being more communicative than observer viewpoint gestures. It has also been suggested that gesture viewpoint is connected with the transitivity of the clause that it accompanies, and it was found in our study that respondents appeared to obtain syntactic information about the associated clause from the gesture. This conclusion was based on the observation that when respondents attempted to report what information was contained in gestures, viewed in the absence of speech, there was a significantly higher proportion of transitive structures in their answers after they had watched character viewpoint gestures compared with observer viewpoint gestures. Communication about the syntax of the accompanying clause might thus be a critical, but thus far neglected, aspect of the role of gestures in everyday talk.