Human interaction has two principle functions: building and maintaining relationships with others and exchanging information. The function of building and maintaining relationships with others relates to interpersonal coordination; this behavior pattern is expected to predict the outcome of social relationships, such as between therapists and patients. It is unclear, however, whether the exchange of information is associated with interpersonal coordination. In the present study, we tested a hypothesis of whether body movement synchrony occurs in a natural conversation and whether this synchrony has a positive correlation with the degree of information exchange. Fifty participants were engaged in a conversation task; each had different roles in the conversation. We measured their body movements during this conversation using an optical motion capture system. Similar to methods that can be found in previous research, we calculated body movements and quantified their synchrony applying the methods previously reported that automatically quantified their body movements. Moreover, we determined the participants' degree of information exchange concerning the conversation using a questionnaire. We observed that the body movement synchrony of pairs who talked with each other was significantly higher than that of pairs who did not talk with each other, and that this synchrony was positively associated with the degree of information exchange. These results suggest that body movement synchrony predicted information exchange.

In a meeting, two or more individuals come together to verbally share information. However, discrepancies in perceptions often occur in complicated discussions. Therefore, whether the information transfer succeeded must be reconfirmed. This problem is typically resolved through ex-post measures such as meeting minutes. Our previous results indicated that the degree of information transfer can be predicted using head movement synchrony. In this study, we propose an information transfer estimation method based on head movement synchrony during a conversation evaluated by an omnidirectional camera that can easily obtain body movements. These body movements were quantified using Motion Energy Analysis, which is commonly used in clinical psychology, with additional processes used to reduce noise caused by lighting in the room and resulting from large accidental movements. By these processes, body movement synchrony was quantified. We confirmed that this synchrony occurred between actually interacting pairs and tested whether it was related to the degree of information transfer. In the experimental evaluation, body movement synchrony was found to be high for interacting pairs, and a positive correlation was observed between synchrony and degree of information transfer. Therefore, our proposed method may detect the synchrony and estimate the degree of information transfer using an omnidirectional camera.