We built an acoustical telepresence robot, called TeleHead, which has a user-like dummy head (i.e., the shape of the dummy head and that of the user is very alike) and whose movement is synchronized with the user's head movement in real time. We are trying to clarify the effects of reproducing the user's head movement. In this article, we eval uated the sense of incongruity caused by the delay time of reproducing head movement by means a psychophysical approach. Discrimination tasks for

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... ement delay clarified the users' perceptual thresholds against the dead time. The results indicate that head-movement control should have a dead time shorter than 28 [ms]. In addition, this dead time does not depend on the characteristics of an acoustical telepresence robot.