An Exploration of Social Grouping in Robots: Effects of Behavioral Mimicry, Appearance, and Eye Gaze

An Exploration of Social Grouping in Robots: Effects of Behavioral Mimicry, Appearance, and Eye Gaze Ahsan I. Nawroj 1 , Mariya Toneva 2 , Henny Admoni 2 , Brian Scassellati 1,2 ahsan.nawroj@yale.edu mariya.toneva@yale.edu henny@cs.yale.edu scaz@cs.yale.edu 1 Department of Mechanical Engineering and Material Science, Yale University 2 Department of Computer Science, Yale University Abstract People naturally and easily establish social groupings based on appearance, behavior, and other nonverbal signals. How- ever, psychologists have yet to understand how these varied signals interact. For example, which factor has the strongest effect on establishing social groups? What happens when two of the factors conflict? Part of the difficulty of answering these questions is that people are unique and stochastic stimuli. To address this problem, we use robots as a visually simple and precisely controllable platform for examining the relative in- fluence of social grouping features. We examine how behav- ioral mimicry, similarity of appearance, and direction of gaze influence peoples’ perception of which group a robot belongs to. Experimental data shows that behavioral mimicry has the most dominant influence on social grouping, though this influ- ence is modulated by appearance. Non-mutual gaze was found to be a weak modulator of the perception of grouping. These results provide insight into the phenomenon of social group- ing, and suggest areas for future exploration. Keywords: Attention; Mimicry; Appearance; Grouping; Per- ception. Introduction People naturally categorize others into social groups. These categorizations are made quickly and often depend on super- ficial factors such as behavioral mimicry, physical similar- ity, and directed eye gaze. Despite their superficial nature, social grouping decisions can have lasting impacts on judg- ments about those groups (Tajfel, 2010). Behavioral mimicry involves adopting the nonverbal be- havior of an interaction partner (Baaren, Janssen, Chartland, & Dijksterhuis, 2009). Previous research identifies the im- portance of behavioral mimicry in the perception of human grouping. According to earlier findings, behavioral mimicry can be used to include oneself in a social group (Lakin, Char- trand, & Arkin, 2008). Moreover, some argue it facilitates social communication by increasing affiliation, which results in strengthened relationships (Lakin, Jefferis, Cheng, & Char- trand, 2003; Stel & Vonk, 2010; Baaren, Holland, Kawakami, & Knippenberg, 2004). The effects of behavioral mimicry are not limited to the partners in the exchange. Non-participating observers are known to view interactions with greater de- gree of nonverbal mimicry as more positive (Bernieri, Gillis, Davis, & Grahe, 1996; Parrill & Kimbara, 2006). Likewise, physical appearance is an important factor, as research shows that the presence of similarities between the physical features of interacting parties increases their classi- fication as a cohesive group (Dasgupta, Banaji, & Abelson, 1999). It is suggested that this increase occurs because phys- ical appearance is a salient perceptual feature which evokes the belief that similar group members also share some psy- chological characteristics (Campbell, 1958; Duncan, 1976; Sagar & Schofield, 1980). Direction of gaze is also identified as a factor in some social groupings. Groups of interaction partners in a con- versational setting are found to be influenced by gaze direc- tion (Sacks, Schegloff, & Jefferson, 1974; Goodwin, 1981). While there is some evidence that eye gaze may be an influ- ential factor in the perception of human groups, the lack of support for an effect in a wider range of groupings suggests that this influence may not be generalized to other types of groups. However, gaze direction may enhance the influence of other factors by increasing awareness of them: it is known to cue the attention of an observer (Hietanen, 1999, 2003) even at ages as early as 5 months (Scaife & Bruner, 1975; Farroni, Johnson, Brockbank, & Simion, 2000). The perception of social interactions and grouping in ex- changes between humans and machines can also be influ- enced by behavior mimicry, appearance, and gaze. The ef- fect of behavioral mimicry is investigated in a study show- ing that humans rate exchanges in which their facial gestures are mimicked by a robot as more favorable than those with- out any mimicry (Riek & Robinson, 2008). There is further evidence that a seemingly trivial physical similarity, such as wearing an armband of the same color as a marked com- puter, induces humans to assess computers of the same color as more similar to themselves as compared to computers of different colors (Nass & Moon, 2000). Another recent study suggests that variations in the proportion of interaction time during which a robot’s gaze is directed towards a person can influence whether that person feels like a member of a group (Mutlu, Shiwa, Kanda, Ishiguro, & Hagita, 2009). While previous studies have examined the influence of be- havioral mimicry, physical appearance, and gaze in perceiv- ing both human and human-robot groupings, none have ex- plored more than one of these important factors at a time. The current experiment systematically varied these factors in order to determine their relative importance. Robots provide an excellent platform for testing such ef- fects. Because their appearance and behavior can be pre- cisely manipulated, robots allow researchers to perform stud- ies that involve carefully varying multiple factors. Addition- ally, anatomically realistic motions enhance the impression of agency (MacDorman, 2006), thereby increasing the possibil- ity of generalization to human social interaction. Our hypotheses were as follows: