Proceedings of the Annual Meeting of the Cognitive Science Society

An influential claim about co-speech gestures is that they are used as a supplement to unsaid meaning in speech. However, when the gesture is fully synchronized with speech, the supplementary role appears unnecessary. The present study examined whether people use gestures differently when they produce Japanese noun phrases that contain verbs. This study compared an ambiguous noun phrase “Rakka-shiteiru (falling) otoko-no (man’s) keitai (cell-phone),” which can be interpreted following the left branching (LB) structure as “The falling man’s cell-phone ({{falling, man}, cell-phone})” or the right branching (RB) structure as “The man’s cell-phone, which is falling ({falling, {man, cell-phone}}).” This study predicted that the onset of the first gesture would be delayed with the RB structure, as the important chunk {man, cell-phone} is produced later in the utterance than in the LB structure. The results supported the prediction, indicating that the onset of the first gesture tended to be delayed when RB was produced. This finding suggests that people may disambiguate syntactically ambiguous linguistic structures through gesture use.