Primate neural systems process gaze relatively well. Infant chimpanzees aged 10-32 weeks prefer photographs of human faces with eyes open compared to photographs with eyes shut, and with direct gaze compared to averted gaze. By four months of age, human infants can discriminate between faces with direct and averted gaze. In adult humans, direct gaze enhances the memorability of faces and the speed of person categorization. Moreover, direct gaze seems to be the best explanation for sensational reception of Byzantine icons in an artistically rich sixteenth-century Indo-Muslim culture.
Gaze has considerable value in making sense of presence. According to a recent study, mother-infant chimpanzees pairs gaze into each other’s eyes on average about 17 times per hour. Mutual gazing covaried similarly in chimps and humans:
maternal cradling was found to be inversely related to mutual gazing in chimpanzees, such that when mother and young infant are in constant physical contact, there is little mutual gaze. Reduced face-to-face interactions, including reduced amounts of mutual gaze, are found in human cultures that have increased physical contact with infants compared with Western norms. … We purpose that mutual engagement in primates is supported via an interchangeability of tactile and visual modalities [Bard et. al., 2005, pp. 621, 623].
The value of the visual mode, however, depends on its circumstances. If the features of a face are scrambled, infant chimpanzees are indifferent between eyes with direct and averted gaze. Direct gaze from a painting or photograph of a face may create value of the same type as mutual gaze and physical contact, but perhaps not as efficiently.
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