The face-mind link: Why we see minds behind faces, and how others' minds change how we see their face

Social perception of robots is shaped by beliefs about their minds

Roboticists often imbue robots with human-like physical features to increase the likelihood that they are afforded benefits known to be associated with anthropomorphism. Similarly, deepfakes often employ computer-generated human faces to attempt to create convincing simulacra of actual humans. In the present work, we investigate whether perceivers' higher-order beliefs about faces (i.e., whether they represent actual people or android robots) modulate the extent to which perceivers deploy face-typical processing for social stimuli. Past work has shown that perceivers' recognition performance is more impacted by the inversion of faces than objects, thus highlighting that faces are processed holistically (i.e., as Gestalt), whereas objects engage feature-based processing. Here, we use an inversion task to examine whether face-typical processing is attenuated when actual human faces are labeled as non-human (i.e., android robot). This allows us to employ a task shown to be differentially sensitive to social (i.e., faces) and non-social (i.e., objects) stimuli while also randomly assigning face stimuli to seem real or fake. The results show smaller inversion effects when face stimuli were believed to represent android robots compared to when they were believed to represent humans. This suggests that robots strongly resembling humans may still fail to be perceived as "social" due pre-existing beliefs about their mechanistic nature. Theoretical and practical implications of this research are discussed.

Perceptual discrimination in the face perception of robots is attenuated compared to humans

When interacting with groups of robots, we tend to perceive them as a homogenous group where all group members have similar capabilities. This overgeneralization of capabilities is potentially due to a lack of perceptual experience with robots or a lack of motivation to see them as individuals (i.e., individuation). This can undermine trust and performance in human-robot teams. One way to overcome this issue is by designing robots that can be individuated such that each team member can be provided tasks based on its actual skills. In two experiments, we examine if humans can effectively individuate robots: Experiment 1 (n = 225) investigates how individuation performance of robot stimuli compares to that of human stimuli that either belong to a social ingroup or outgroup. Experiment 2 (n = 177) examines to what extent robots' physical human-likeness (high versus low) affects individuation performance. Results show that although humans are able to individuate robots, they seem to individuate them to a lesser extent than both ingroup and outgroup human stimuli (Experiment 1). Furthermore, robots that are physically more humanlike are initially individuated better compared to robots that are physically less humanlike; this effect, however, diminishes over the course of the experiment, suggesting that the individuation of robots can be learned quite quickly (Experiment 2). Whether differences in individuation performance with robot versus human stimuli is primarily due to a reduced perceptual experience with robot stimuli or due to motivational aspects (i.e., robots as potential social outgroup) should be examined in future studies.

Robots engage face-processing less strongly than humans

Robot faces often differ from human faces in terms of their facial features (e.g., lack of eyebrows) and spatial relationships between these features (e.g., disproportionately large eyes), which can influence the degree to which social brain [i.e., Fusiform Face Area (FFA), Superior Temporal Sulcus (STS); Haxby et al., 2000] areas process them as social individuals that can be discriminated from other agents in terms of their perceptual features and person attributes. Of interest in this work is whether robot stimuli are processed in a less social manner than human stimuli. If true, this could undermine human-robot interactions (HRIs) because human partners could potentially fail to perceive robots as individual agents with unique features and capabilities-a phenomenon known as outgroup homogeneity-potentially leading to miscalibration of trust and errors in allocation of task responsibilities. In this experiment, we use the face inversion paradigm (as a proxy for neural activation in social brain areas) to examine whether face processing differs between human and robot face stimuli: if robot faces are perceived as less face-like than human-faces, the difference in recognition performance for faces presented upright compared to upside down (i.e., inversion effect) should be less pronounced for robot faces than human faces. The results demonstrate a reduced face inversion effect with robot vs. human faces, supporting the hypothesis that robot faces are processed in a less face-like manner. This suggests that roboticists should attend carefully to the design of robot faces and evaluate them based on their ability to engage face-typical processes. Specific design recommendations on how to accomplish this goal are provided in the discussion.

The uncanniness of written text is explained by configural deviation and not by processing disfluency

Deviating from human norms in human-looking artificial entities can elicit uncanny sensations, described as the uncanny valley. This study investigates in three tasks whether configural deviation in written text also increases uncanniness. It further evaluates whether the uncanniness of text is better explained by perceptual disfluency and especially deviations from specialized categories, or conceptual disfluency caused by ambiguity. In the first task, lower sentence readability predicted uncanniness, but deviating sentences were more uncanny than typical sentences despite being just as readable. Furthermore, familiarity with a language increased the effect of configural deviation on uncanniness but not the effect of non-configural deviation (blur). In the second and third tasks, semantically ambiguous words and sentences were not uncannier than typical sentences, but deviating, non-ambiguous sentences were. Deviations from categories with specialized processing mechanisms thus better fit the observed results as an explanation of the uncanny valley than ambiguity-based explanations.

Perceiving People With Physical Disabilities as Overcoming Adversity Warps Mind Perception

Across six studies, we tested how people with physical disabilities were ascribed mental faculties. People with physical disabilities were seen as more capable of mental agency (e.g., thinking), but not more capable of experience (e.g., pain), compared to nondisabled people (Study 1). People with physical disabilities were also seen as more capable of supernatural mental agency (e.g., seeing the future, reading minds; Study 2). Believing that people with physical disabilities were more mentally agentic than nondisabled people was unrelated to Beliefs in a Just World (Study 3) but was related to beliefs about hardship (Study 4). Narratives of overcoming adversity, common in portrayals of the disabled community, increased the perceived mental sophistication of people with physical disabilities (Study 5). Finally, hardship narratives also affected helping behavior toward people with physical disabilities (Study 6). Thus, hardship stories surrounding individuals with disabilities may contribute to beliefs that they have particularly sophisticated minds.

Bodies and Minds: Heavier Weight Targets Are De-Mentalized as Lacking in Mental Agency

Five experiments investigate the hypothesis that heavier weight individuals are denied mental agency (i.e., higher order cognitive and intentional capacities), but not experience (e.g., emotional and sensory capacities), relative to average weight individuals. Across studies, we find that as targets increase in weight, they are denied mental agency; however, target weight has no reliable influence on ascriptions of experience (Studies 1a-2b). Furthermore, the de-mentalization of heavier weight targets was associated with both disgust and beliefs about targets' physical agency (Study 3). Finally, de-mentalization affected role assignments. Heavier weight targets were rated as helpful for roles requiring experiential but not mentally agentic faculties (Study 4). Heavier weight targets were also less likely than chance to be categorized into a career when it was described as requiring mental agency (versus experience; Study 5). These findings suggest novel insights into past work on weight stigma, wherein discrimination often occurs in domains requiring mental agency.

The timeline of mentalization: Distinguishing a two-phase process from mind detection to mind attribution

Mentalization is the ability to perceive other people's mental states. This research aimed to deepen our understanding of the underlying mechanisms while also exploring the timeline of the mentalization process. Two studies were conducted in which participants' electrophysiological activity was measured while elaborating Black and White (Study 1), or Italian (ingroup) and Romanian (outgroup), human and doll-like faces (Study 2). Moreover, in Study 2 the presented faces differed in their Facial Width-to-Height Ratio. Subsequently, an Implicit Mind Attribution Test (IMAT) measured the strength of the association of the same ingroup and outgroup human stimuli with mind and body-related words. Two different phases in the time course of the mentalization process emerged. An early ERP component (N170) indicated a first difference between doll-like, mindless and human, mindful targets, while a later ERP component (P300) represented the second stage of mentalization. In this stage, outgroup doll-like faces were elaborated more similarly to the outgroup human faces compared to the same stimuli of the ingroup. Moreover, only a positive correlation between the P300 and the IMAT emerged indicating that the differences in this later ERP component were related with an implicit behavioral measure of mind attribution. These results stipulate the timeline of the mentalization process that is defined by an initial moment of mind detection, in which mindful and mindless stimuli are differentiated for the first time, and a second phase of mind attribution, where the interplay of perceptual and contextual information determine the extraction of a mind from a face.

The Uncanny Valley Phenomenon and the Temporal Dynamics of Face Animacy Perception

Human replicas highly resembling people tend to elicit eerie sensations-a phenomenon known as the uncanny valley. To test whether this effect is attributable to people's ascription of mind to (i.e., mind perception hypothesis) or subtraction of mind from androids (i.e., dehumanization hypothesis), in Study 1, we examined the effect of face exposure time on the perceived animacy of human, android, and mechanical-looking robot faces. In Study 2, in addition to exposure time, we also manipulated the spatial frequency of faces, by preserving either their fine (high spatial frequency) or coarse (low spatial frequency) information, to examine its effect on faces' perceived animacy and uncanniness. We found that perceived animacy decreased as a function of exposure time only in android but not in human or mechanical-looking robot faces (Study 1). In addition, the manipulation of spatial frequency eliminated the decrease in android faces' perceived animacy and reduced their perceived uncanniness (Study 2). These findings link perceived uncanniness in androids to the temporal dynamics of face animacy perception. We discuss these findings in relation to the dehumanization hypothesis and alternative hypotheses of the uncanny valley phenomenon.

Understanding dual realities and more in VR

The five commentaries on our paper (Pan & Hamilton, 2018, Br. J. Psychol.) provide a useful summary of the key issues we raise, and also bring to the foreground some new and important questions, touching on a range of issues including presence and the conceptualization of dual realities. We highlight here some important themes and directions for future investigation.