Personal Space Toward Human-Like and Non-Human-Like Robots: Effects of Robot Appearance and Likability

In this study, we investigated how robot appearance—human-like versus non-human-like—affects per- sonal space during direct robot approaches from eight direc- tions and examined the relationship between personal space and perceived likability. Twenty-three Japanese male participants participated in the experiment. The participants remained stationary while each robot approached from different direc- tions (0◦–315◦in 45◦increments), and the distance at which discomfort was perceived was recorded as the personal space threshold. Likability was assessed via a questionnaire. Across all conditions, a consistent negative correlation was observed between likability and personal space: participants who rated the robot more favorably tended to allow it to approach them more closely. No significant differences in personal space or likability were found between the two appearance conditions. However, the Human-like condition showed an almost circular personal space shape with an approximate radius of 1.35 m, slightly extended in its rear part, whereas the Non-human- like condition tended to have a personal space shape with a larger front and smaller rear parts. These results indicate that likability is closely associated with interpersonal distance regulation and suggest that manipulating perceived likability may serve as an effective strategy for managing personal space in service and interactive robot contexts. These findings may inform robot design approaches aimed at maintaining socially comfortable distances and improving overall user acceptance.