Robot gaze does not reflexively cue human attention

Robot gaze does not reflexively cue human attention Henny Admoni, Caroline Bank, Joshua Tan, Mariya Toneva and Brian Scassellati Department of Computer Science, Yale University 51 Prospect Street, New Haven, CT 06511 USA henny@cs.yale.edu, caroline.bank@yale.edu, joshua.tan@aya.yale.edu, mariya.toneva@yale.edu, scaz@cs.yale.edu Abstract Joint visual attention is a critical aspect of typical human inter- actions. Psychophysics experiments indicate that people ex- hibit strong reflexive attention shifts in the direction of another person’s gaze, but not in the direction of non-social cues such as arrows. In this experiment, we ask whether robot gaze elicits the same reflexive cueing effect as human gaze. We consider two robots, Zeno and Keepon, to establish whether differences in cueing depend on level of robot anthropomorphism. Us- ing psychophysics methods for measuring attention by analyz- ing time to identification of a visual probe, we compare atten- tion shifts elicited by five directional stimuli: a photograph of a human face, a line drawing of a human face, Zeno’s gaze, Keepon’s gaze and an arrow. Results indicate that all stimuli convey directional information, but that robots fail to elicit at- tentional cueing effects that are evoked by non-robot stimuli, regardless of robot anthropomorphism. Introduction Joint visual attention is an important aspect of typical so- cial interactions. A single gaze communicates information— there are predators hiding behind that tree; a tasty source of food is over there; you are crossing into my territory— and supports social conventions such as conversational turn- taking and joint referencing. As robots become more inte- grated into daily human life, social interactions occur with increasing frequency between humans and robots, as well: robots assist nurses in hospitals, act as companions for the elderly, and interact with children in schools and in therapy. In this paper, we investigate whether people are responsive to joint attention cues from robots. We focus on one aspect of joint attention: recognizing the direction of another person’s gaze and shifting one’s own attention in that direction. Evidence from psychophysics suggests that typical humans readily shift their attention in response to a directional cue, such as averted eyes or an arrow. In traditional non-predictive cueing experiments, participants view a centrally-presented stimulus followed by a peripherally-presented visual probe, and press a keyboard key in response to the probe. Key press response times are theoretically correlated with atten- tion: participants will respond more quickly to probes located in the direction to which they are already attending. Studies have found that when the stimulus contains directional infor- mation (such as a face with averted eyes, or an arrow point- ing in one direction), people respond more quickly to probes at cued locations, in which the probe is on the same side as indicated by the stimulus, than to probes at uncued locations, even when they are told that the cue does not indicate probe location and should be ignored (Downing, Dodds, & Bray, 2004; Driver et al., 1999; Friesen & Kingstone, 1998; Lang- ton & Bruce, 1999). Attention shifting via directional cue seems to be an early and reflexive skill for humans: children as young as three months old attend more quickly to a periph- eral probe on cued trials than on uncued trials when the cue is a human face (Hood, Willen, & Driver, 1998). When cues are counterpredictive of probe location, how- ever, social stimuli such as faces and eyes elicit different pat- terns of behavior than other directional stimuli. In counter- predictive cueing paradigms, probes appear with significantly higher probability opposite the location cued by centrally- located stimuli (Driver et al., 1999). For example, when the centrally-located stimulus is directed toward the left, probes have a 75% chance of appearing to the right of center, and vice versa. In counterpredictive experiments, it is beneficial for participants to orient attention away from the cued di- rection; therefore, shorter response times to probes in cued directions are attributed to reflexive or uncontrollable atten- tion shifts. In contrast, shorter response times to probes in uncued (but predicted) locations are interpreted as voli- tional orienting of attention. Counterpredictive experiments reveal that participants reflexively orient in the direction of eyes (Driver et al., 1999) but volitionally orient away from the direction of arrows (Friesen, Ristic, & Kingstone, 2004) or extended tongues (Downing et al., 2004). A stimulus that is ambiguously social will elicit reflexive attention shifts when presented to participants as a social cue (a picture of eyes), but not when presented as a non-social cue (a picture of a car) (Ristic & Kingstone, 2005). Furthermore, the effect of this cue on reflexive attention persists if the cue is presented first as social and then as non-social, but not vice versa. This reflexive cueing effect seems strongest for faces, but not nec- essarily unique to them: arrows have also been shown to trig- ger reflexive orienting, with magnitude of reflexive orienting toward arrow cues positively correlated with individuals’ vol- untary attention control (Tipples, 2008), suggesting that dis- similarities in attention directed at eyes and arrows are differ- ences of magnitude (strong versus weak), rather than of kind (reflexive versus volitional). Eye-tracking and brain-imaging studies reveal similar re- sults. People make more erroneous eye saccades in the di- rection of a “distracter” cue they are told to ignore if that cue is a face, rather than an arrow (Ricciardelli, Bricolo, Agli- oti, & Chelazzi, 2002). Functional MRI studies show that the same cue activates different neural pathways depending on whether it is perceived as eyes or as a non-social direc- tional image (Kingstone, Tipper, Ristic, & Ngan, 2004). At- tentional orienting to gaze cues and to arrow cues activates different cortical networks, with attentional orienting to arrow