In this study, we investigate the effects of the emergence of joint attention in social interaction consisting of two robots and one person. Especially, we focus on synchronous behaviors of two robots and the degree of communication activity caused by their behaviors. We predict that when two robots communicate with each other using synchronous behaviors, the degree of communication activity between them is observed to become higher. Moreover, as a person close to two robots becomes easily involved in their communication, joint attention among them will emerge there when the robots turn their eyes to the person. For verifying this prediction, we conducted two experiments to investigate whether a direction of participants' eyes were guided by two robots' eyes and heads movements. Results of the experiments showed that when two robots gazed at a participant at the high degree of communication activity, the direction of his/her eyes was easily guided by two robots' eyes and heads movements.

For realizing smooth communication, participants' viewpoints and usages of demonstrative pronouns assume an important role. Moreover, they both are strongly associated and construct a dialogue structure among participants. In this study, we investigate the relation constructed by their viewpoints and usages of demonstrative pronouns in a small group. Especially, we conducted experiments to verify whether demonstrative pronouns were unified in a small group consisted of two participants and a robot guided by the robot, and evaluate participants' psychological factors on this occasion. As a result of experiments, the unification of demonstrative pronouns in the small group guided by the robot led participants to smooth communication.

In this study, we investigate the two effects of joint attention, building relationships and sharing recognition, in group interaction consisting of two robots and one person. The building relationship is focused on entrainment resulting from the two robots' gazing at one person, while the sharing recognition refers to an original effect of the joint attention in a group interaction featuring the shared focus of individuals on one object. Results of experiments on the building relationships aspect showed that when two robots gazed at a person, he/she tended to be more immersed in communication with the robots. In the case of sharing recognition, when the two robots gazed at the target synchronously, the person could share it more correctly than when it was done asynchronously.