How macaques view familiarity and gaze in conspecific faces.

Abstract

The pattern of visual fixations on an image depends not only on the image content but also on the viewer's disposition and on the function (or pathology) of underlying neural circuitry. For example, human viewers display changes in viewing patterns toward face images that differ in gaze direction or in the viewer's familiarity with the face. Macaques share many face processing abilities with humans, and their neural circuitry is used to understand perception across species, yet their viewing responses to gaze and familiarity of faces is poorly understood. In this study, rhesus macaques passively viewed faces of familiar and unfamiliar conspecifics whose head-and-eye gaze was directed either toward or away from the viewing monkey. The eyes of faces were viewed more than any other feature; furthermore, familiar eyes were viewed more than unfamiliar eyes. In contrast, ears, though not as salient as eyes, were viewed about twice as often for unfamiliar faces as familiar faces. Directed-gaze eyes were fixated earlier, and for a greater proportion of saccades than were the eyes of averted-gaze faces, suggesting that mutual gaze attracts a more immediate and sustained scanning of the eyes. Ears and external features were more salient for averted, as compared with directed gaze. In general, effects were more robust (within and across subjects) for the gaze contrast than for familiarity, perhaps as a consequence of the greater image-based differences for the gaze than the familiarity stimuli used in this study.

Rudimentary empathy in macaques’ social decision-making

“…These associations indicate that, in the context of juice allocation, mutual gaze could express an intrinsic motivation for social affiliation. Thus, consistently with other observations, we suggest that monkeys' eye contact can also represent a form of positive social interaction (44,(48)(49)(50). The vicarious reward hypothesis suggests that viewing a conspecific receiving juice might activate, through some form of mirror mechanism, the same reward circuit as an actual drop of juice (33).…”

Social relevance drives viewing behavior independent of low-level salience in rhesus macaques

“…Studies investigating social perception have almost exclusively used images of faces cropped from the body, finding that both rhesus macaques (Keating and Keating, 1982; Mendelson et al, 1982; Wilson and Goldman-Rakic, 1994; Guo et al, 2003, 2006; Gothard et al, 2004, 2009; Deaner et al, 2005; Ghazanfar et al, 2006; Nahm et al, 2008; Leonard et al, 2012) and humans (Haith et al, 1977; Walker-Smith et al, 1977; Janik et al, 1978; Althoff and Cohen, 1999; Henderson et al, 2005) prefer to view faces, particularly the eye region, compared to other stimuli. However, in natural settings, faces are rarely seen in isolation from bodies and other individuals and objects.…”

Seeing two faces together: preference formation in humans and rhesus macaques

“…More specifically, these studies have shown that the spatial distribution of eye fixations is modulated by conspecificity, the eyeregion of conspecific faces receiving more attention than other face parts. Familiarity, defined as being an in-group member, and direct versus averted gaze also influenced single face scanning in macaques (Leonard et al 2012). Again, the eyes of familiar individuals received more attention than the eyes of unfamiliar conspecifics.…”