Personal Space Violation by a Robot: An Application of Expectation Violation Theory in Human-Robot Interaction

Studies of personal space between human and robot have been growing. However, little is known about the effects of personal space violation by a robot. Expectation Violation Theory (EVT) explains how people respond to personal space invasion by another person, depending on if the person is perceived as rewarding or punishing. This study aims to extend EVT to HRI and to examine the effects of personal space violation using EVT as an analytical framework. A 2 × 5 within-subject experimental design was employed. The participants were approached by two robots with different reward value (rewarding and punishing) at varying distances (threat, near, norm, slightly far, and far distances). The participants were asked to rate the robots’ perceived warmth, competence, and comfort scores after each approach to evaluate the communication outcomes after the personal space violation occurred. The results suggested that approaching distances had influences on the communication outcomes. As predicted by EVT, how each distance affected the communication outcomes differ according on robot’s reward value. The findings indicated that EVT was partially successful in predicting the effects of personal space violations depending on the reward value and approaching distance of a robot. This study has provided a partial support that EVT can be applied to HRI and contributed to understanding the effects of personal space violation by a robot. When considering personal space in HRI, perceived reward value of the robot plays an important role as it can influence the effects of the personal space violation greatly.