Making eye contact with a robot: Psychophysiological responses to eye contact with a human and with a humanoid robot

Autonomic and facial electromyographic responses to watching eyes

We measured participants' psychophysiological responses and gaze behavior while viewing a stimulus person's direct and averted gaze in three different conditions manipulating the participants' experience of being watched. The results showed that skin conductance responses and heart rate deceleration responses were greater to direct than averted gaze only in the condition in which the participants had the experience of being watched by the other individual. In contrast, gaze direction had no effects on these responses when the participants were manipulated to believe that the other individual could not watch them or when the stimulus person was presented in a pre-recorded video. Importantly, the eye tracking measures showed no differences in participants' looking behavior between these stimulus presentation conditions. The results of facial electromyography responses suggested that direct gaze elicited greater zygomatic and periocular responses than averted gaze did, independent of the presentation condition. It was concluded that the affective arousal and attention-orienting indexing autonomic responses to eye contact are driven by the experience of being watched. In contrast, the facial responses seem to reflect automatized affiliative responses which can be elicited even in conditions in which seeing another's direct gaze does not signal that the self is being watched.

Examining the Impact of Digital Human Gaze Expressions on Engagement Induction

With advancements in technology, digital humans are becoming increasingly sophisticated, with their application scope widening to include interactions with real people. However, research on expressions that facilitate natural engagement in interactions between real people and digital humans is scarce. With this study, we aimed to examine the differences in user engagement as measured by subjective evaluations, eye tracking, and electroencephalogram (EEG) responses relative to different gaze expressions in various conversational contexts. Conversational situations were categorized as face-to-face, face-to-video, and digital human interactions, with gaze expressions segmented into eye contact and gaze avoidance. Story stimuli incorporating twelve sentences verified to elicit positive and negative emotional responses were employed in the experiments after validation. A total of 45 participants (31 females and 14 males) underwent stimulation through positive and negative stories while exhibiting eye contact or gaze avoidance under each of the three conversational conditions. Engagement was assessed using subjective evaluation metrics in conjunction with measures of the subjects' gaze and brainwave activity. The findings revealed engagement disparities between the face-to-face and digital-human conversation conditions. Notably, only positive stimuli elicited variations in engagement based on gaze expression across different conversation conditions. Gaze analysis corroborated the engagement differences, aligning with prior research on social sensitivity, but only in response to positive stimuli. This research departs from traditional studies of un-natural interactions with digital humans, focusing instead on interactions with digital humans designed to mimic the appearance of real humans. This study demonstrates the potential for gaze expression to induce engagement, regardless of the human or digital nature of the conversational dyads.

Psychophysiological responses to eye contact with a humanoid robot: Impact of perceived intentionality

Eye contact with a social robot has been shown to elicit similar psychophysiological responses to eye contact with another human. However, it is becoming increasingly clear that the attention- and affect-related psychophysiological responses differentiate between direct (toward the observer) and averted gaze mainly when viewing embodied faces that are capable of social interaction, whereas pictorial or pre-recorded stimuli have no such capability. It has been suggested that genuine eye contact, as indicated by the differential psychophysiological responses to direct and averted gaze, requires a feeling of being watched by another mind. Therefore, we measured event-related potentials (N170 and frontal P300) with EEG, facial electromyography, skin conductance, and heart rate deceleration responses to seeing a humanoid robot's direct versus averted gaze, while manipulating the impression of the robot's intentionality. The results showed that the N170 and the facial zygomatic responses were greater to direct than to averted gaze of the robot, and independent of the robot's intentionality, whereas the frontal P300 responses were more positive to direct than to averted gaze only when the robot appeared intentional. The study provides further evidence that the gaze behavior of a social robot elicits attentional and affective responses and adds that the robot's seemingly autonomous social behavior plays an important role in eliciting higher-level socio-cognitive processing.

Skin conductance, facial EMG, and heart rate responses in multi-person gaze interactions

Previous literature has reported enhanced affective and attentional responses to faces with a direct vs. averted gaze. Typically, in these studies, only single faces were presented. However, daily social encounters often involve interaction with more than just one person. By employing an experimental set-up in which the participants believed they were interacting with two other persons, the present study, for the first time, investigated participants' skin conductance, facial electromyographic (EMG), and heart rate deceleration responses in multi-person eye contact situations. Responses were measured in two different social contexts; i) when the participants observed eye contact between two other persons ('vicarious eye contact effect'), and ii) when the participants themselves received direct gaze either from one or two persons. The results showed that the skin conductance, facial EMG, and heart rate deceleration responses elicited by observing two other persons making eye contact did not differ from those elicited by observing one person looking at the other while the other person was not reciprocating with their gaze. As a novel finding, the results showed that receiving direct gaze from two persons elicited greater affective arousal and zygomatic EMG, but smaller heart rate deceleration responses in participants than receiving direct gaze from one person only. The findings are thoroughly discussed and it is concluded that physiological responses in multi-person interaction contexts are influenced by many social effects between the interactors and can be markedly different from those observed in two-person interactions.

Extraction and Evaluation of Greeting Speech-Timing and Characteristic Upper Body Motion for Robots to Gain Attention of Older Adults

Greeting is important for socially assistive robot to smoothly initiate conversations with older adults. Because of their decreased cognitive function, older adults may occasionally be unaware of the presence of a robot. The purpose of this study was to investigate and evaluate the characteristic motion and utterance time for greeting older adults in comparison with those for greeting non-older adults. The motion and utterance for greeting a seated target imitating an older adult and greeting a non-older adult were measured. The utterance times of the greeting and motion parameters such as the maximum joint angles were calculated from the measured data. The parameters were compared using statistical methods. According to the results, the hip bending angle in older adults was 36.6° greater than in the non-older adults. The utterance lag for greeting the older adults was 0.7 s longer than that for greeting the non-older adults at this time. The impressions of the robot that greeted the participants based on the extracted motion parameters were compared to verify these parameter differences. Although the greeting styles did not differ significantly, it was verified that the robot’s greeting was more impressive than that of a computer-graphics robot.

Age-Related Differences in the Perception of Robotic Referential Gaze in Human-Robot Interaction

There is an increased interest in using social robots to assist older adults during their daily life activities. As social robots are designed to interact with older users, it becomes relevant to study these interactions under the lens of social cognition. Gaze following, the social ability to infer where other people are looking at, deteriorates with older age. Therefore, the referential gaze from robots might not be an effective social cue to indicate spatial locations to older users. In this study, we explored the performance of older adults, middle-aged adults, and younger controls in a task assisted by the referential gaze of a Pepper robot. We examined age-related differences in task performance, and in self-reported social perception of the robot. Our main findings show that referential gaze from a robot benefited task performance, although the magnitude of this facilitation was lower for older participants. Moreover, perceived anthropomorphism of the robot varied less as a result of its referential gaze in older adults. This research supports that social robots, even if limited in their gazing capabilities, can be effectively perceived as social entities. Additionally, this research suggests that robotic social cues, usually validated with young participants, might be less optimal signs for older adults.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12369-022-00926-6.

A study on the influence of service robots’ level of anthropomorphism on the willingness of users to follow their recommendations

Service robots are increasingly deployed in various industries including tourism. In spite of extensive research on the user’s experience in interaction with these robots, there are yet unanswered questions about the factors that influence user’s compliance. Through three online studies, we investigate the effect of the robot anthropomorphism and language style on customers’ willingness to follow its recommendations. The mediating role of the perceived mind and persuasiveness in this relationship is also investigated. Study 1 (n = 89) shows that a service robot with a higher level of anthropomorphic features positively influences the willingness of users to follow its recommendations while language style does not affect compliance. Study 2a (n = 168) further confirms this finding when we presented participants with a tablet vs. a service robot with an anthropomorphic appearance while communication style does not affect compliance. Finally, Study 2b (n = 122) supports the indirect effect of anthropomorphism level on the willingness to follow recommendations through perceived mind followed by persuasiveness. The findings provide valuable insight to enhance human–robot interaction in service settings.

Eye contact avoidance in crowds: A large wearable eye-tracking study

Eye contact is essential for human interactions. We investigated whether humans are able to avoid eye contact while navigating crowds. At a science festival, we fitted 62 participants with a wearable eye tracker and instructed them to walk a route. Half of the participants were further instructed to avoid eye contact. We report that humans can flexibly allocate their gaze while navigating crowds and avoid eye contact primarily by orienting their head and eyes towards the floor. We discuss implications for crowd navigation and gaze behavior. In addition, we address a number of issues encountered in such field studies with regard to data quality, control of the environment, and participant adherence to instructions. We stress that methodological innovation and scientific progress are strongly interrelated.

Neural and Affective Responses to Prolonged Eye Contact with One's Own Adolescent Child and Unfamiliar Others

Eye contact is crucial for the formation and maintenance of social relationships, and plays a key role in facilitating a strong parent-child bond. However, the precise neural and affective mechanisms through which eye contact impacts on parent-child relationships remain elusive. We introduce a task to assess parents' neural and affective responses to prolonged direct and averted gaze coming from their own child, and an unfamiliar child and adult. While in the scanner, 79 parents (n = 44 mothers and n = 35 fathers) were presented with prolonged (16-38 s) videos of their own child, an unfamiliar child, an unfamiliar adult, and themselves (i.e., targets), facing the camera with a direct or an averted gaze. We measured BOLD-responses, tracked parents' eye movements during the videos, and asked them to report on their mood and feelings of connectedness with the targets after each video. Parents reported improved mood and increased feelings of connectedness after prolonged exposure to direct versus averted gaze and these effects were amplified for unfamiliar targets compared to their own child, due to high affect and connectedness ratings after videos of their own child. Neuroimaging results showed that the sight of one's own child was associated with increased activity in middle occipital gyrus, fusiform gyrus and inferior frontal gyrus relative to seeing an unfamiliar child or adult. While we found no robust evidence of specific neural correlates of eye contact (i.e., contrast direct > averted gaze), an exploratory parametric analysis showed that dorsomedial prefrontal cortex (dmPFC) activity increased linearly with duration of eye contact (collapsed across all "other" targets). Eye contact-related dmPFC activity correlated positively with increases in feelings of connectedness, suggesting that this region may drive feelings of connectedness during prolonged eye contact with others. These results underline the importance of prolonged eye contact for affiliative processes and provide first insights into its neural correlates. This may pave the way for new research in individuals or pairs in whom affiliative processes are disrupted.

Pupil dilation predicts modulation of direct gaze on action value calculations

Perceiving direct gaze facilitates social cognition and behaviour. We hypothesized that direct gaze modulates decision-making, particularly calculations of action values. To test our hypothesis, we used the reinforcement learning paradigm in situations with or without direct gaze. Forty adults were recruited and participated in pupil size measurements and a two-armed bandit task. The task was conducted with 70% and 30% reward probabilities for each option. During the task, a female showing the Direct Gaze (DG) or Closed Eyes (CE) condition was presented from the start of each trial. The results showed that behavioural bias to choices with 70% reward probability increased more in the DG condition than in the CE condition and the expected reward value. This bias to choices with 70% reward in the DG condition was predicted by pupil dilation to DG. These results suggest that participants over-evaluated the expected reward value in the DG condition, and this DG effect may be related to subjective expectations of rewarding events indexed by pupil dilations. It is considered that perceiving direct gaze is a driver of reward expectations that modulate action value calculations and then cognitive processing and behaviours are facilitated.

Human face and gaze perception is highly context specific and involves bottom-up and top-down neural processing

This review summarizes human perception and processing of face and gaze signals. Face and gaze signals are important means of non-verbal social communication. The review highlights that: (1) some evidence is available suggesting that the perception and processing of facial information starts in the prenatal period; (2) the perception and processing of face identity, expression and gaze direction is highly context specific, the effect of race and culture being a case in point. Culture affects by means of experiential shaping and social categorization the way in which information on face and gaze is collected and perceived; (3) face and gaze processing occurs in the so-called 'social brain'. Accumulating evidence suggests that the processing of facial identity, facial emotional expression and gaze involves two parallel and interacting pathways: a fast and crude subcortical route and a slower cortical pathway. The flow of information is bi-directional and includes bottom-up and top-down processing. The cortical networks particularly include the fusiform gyrus, superior temporal sulcus (STS), intraparietal sulcus, temporoparietal junction and medial prefrontal cortex.

Does a Sense of Social Presence During Conversation Affect Student's Shared Memory? Evidence From SS-RIF Paradigm

People constantly talk to one another about the past, and in so doing, they recount certain details while remaining silent about others. Collaborative or conversational remembering plays an important role in establishing shared representations of the past (e.g., the 911 attacks, Covid-19). According to the socially shared retrieval-induced forgetting (SS-RIF) effect, a listener will forget about relevant but unpracticed information during communication, due to intentional or unintentional selective retrieval of data by the speaker. The SS-RIF paradigm has been applied to explain how collective memory is shaped within the context of conversation/discourse. This study sought to determine if SS-RIF occurred only during face-to-face communication, or whether shared memories could be developed through other types of conversation quite common in modern society. We also investigated whether a level of social interaction in the real-world presence of others is a necessary condition for inducing SS-RIF, and if listeners experience different degrees of SS-RIF due to different levels of perceived social presence. We observed the SS-RIF phenomenon in listeners both in real life and video; the degree of forgetting was the same for the two conditions. These results indicate that social presence may not be associated with SS-RIF. Public silence affects the formation of collective memory regardless of the face-to-face presence of others, and thus physical presence is not necessary to induce SS-RIF.

Robot Gaze Behavior Affects Honesty in Human-Robot Interaction

As the use of humanoid robots proliferates, an increasing amount of people may find themselves face-to-“face” with a robot in everyday life. Although there is a plethora of information available on facial social cues and how we interpret them in the field of human-human social interaction, we cannot assume that these findings flawlessly transfer to human-robot interaction. Therefore, more research on facial cues in human-robot interaction is required. This study investigated deception in human-robot interaction context, focusing on the effect that eye contact with a robot has on honesty toward this robot. In an iterative task, participants could assist a humanoid robot by providing it with correct information, or potentially secure a reward for themselves by providing it with incorrect information. Results show that participants are increasingly honest after the robot establishes eye contact with them, but only if this is in response to deceptive behavior. Behavior is not influenced by the establishment of eye contact if the participant is actively engaging in honest behavior. These findings support the notion that humanoid robots can be perceived as, and treated like, social agents, since the herein described effect mirrors one present in human-human social interaction.

Development Issues of Healthcare Robots: Compassionate Communication for Older Adults with Dementia

Although progress is being made in affective computing, issues remain in enabling the effective expression of compassionate communication by healthcare robots. Identifying, describing and reconciling these concerns are important in order to provide quality contemporary healthcare for older adults with dementia. The purpose of this case study was to explore the development issues of healthcare robots in expressing compassionate communication for older adults with dementia. An exploratory descriptive case study was conducted with the Pepper robot and older adults with dementia using high-tech digital cameras to document significant communication proceedings that occurred during the activities. Data were collected in December 2020. The application program for an intentional conversation using Pepper was jointly developed by Tanioka’s team and the Xing Company, allowing Pepper’s words and head movements to be remotely controlled. The analysis of the results revealed four development issues, namely, (1) accurate sensing behavior for “listening” to voices appropriately and accurately interacting with subjects; (2) inefficiency in “listening” and “gaze” activities; (3) fidelity of behavioral responses; and (4) deficiency in natural language processing AI development, i.e., the ability to respond actively to situations that were not pre-programmed by the developer. Conversational engagements between the Pepper robot and patients with dementia illustrated a practical usage of technologies with artificial intelligence and natural language processing. The development issues found in this study require reconciliation in order to enhance the potential for healthcare robot engagement in compassionate communication in the care of older adults with dementia.