Linguistic influences on gesture’s form

Hand gestures in face-to-face dialogue are symbolic acts, integrated with speech. Little is known about the factors that determine the physical form of these gestures. When the gesture depicts a previous nonsymbolic action, it obviously resembles this action; however, such gestures are not only noticeably different from the original action but, when they occur in a series, are different from each other. This paper presents an experiment with two separate analyses (one quantitative, one qualitative) testing the hypothesis that the immediate communicative function is a determinant of the symbolic form of the gesture. First, we manipulated whether the speaker was describing the previous action to an addressee who had done the same actions and therefore shared common ground or to one who had done different actions and therefore did not share common ground. The common ground gestures were judged to be significantly less complex, precise, or informative than the latter, a finding similar to the effects of common ground on words. In the qualitative analysis, we used the given versus new principle to analyze a series of gestures about the same actions by the same speaker. The speaker emphasized the new information in each gesture by making it larger, clearer, etc. When this information became given, a gesture for the same action became smaller or less precise, which is similar to findings for given versus new information in words. Thus the immediate communicative function (e.g., to convey information that is common ground or that is new) played a major role in determining the physical form of the gestures.