Human faces convey abundant social information. The influence of social information on duration estimation was examined by comparing a cartoon face (CF; social) condition with geometric plane figures, or CFs with internal elements disturbed from their normal position (non-social) condition, and also by comparing a human portrait facing the front (more social interaction) condition with the portrait facing the back (less social interaction) condition. Results showed that in the supra-second range, both CFs and human portraits facing the front led to an underestimation compared with non-social or less social information conditions. In the sub-second range, only portraits facing the front were overestimated compared with those facing the back and with the CFs. These results suggest that in the millisecond range, the biological information conveyed by faces may lead to higher arousal, which may result in accelerated clock speed and overestimation. In the supra-second range, it is possible that attention was diverted by social information, resulting in duration underestimation. Taken together, our results suggest that the different mechanisms were involved in duration perception of social information conveyed by face feature in the sub-and supra-second range.

Gazing is important during communication, which is a type of body language that differs from culture to culture. The present study investigated the influence of direct and averted gaze directions on the perceived duration of gazing among same-race and other-race faces. The gaze direction effect, in which direct-gazing faces were perceived to be longer than averted-gazing faces were, was found in the same-race condition but not in the other-race condition. The results could promote our understanding of the underlying mechanism of the gaze direction effect based on the perception of interpersonal social interaction.