The Upper Eye Bias: Rotated Faces Draw Fixations to the Upper Eye

A prosocial function of head-gaze aversion and head-cocking in common marmosets

Gaze aversion is a behavior adopted by several mammalian and non-mammalian species in response to eye contact, and is usually interpreted as a reaction to a perceived threat. Unlike many other primate species, common marmosets (Callithrix jacchus) are thought to have a high tolerance for direct gaze, barely exhibiting gaze avoidance towards conspecifics and humans. Here we show that this does not hold for marmosets interacting with a familiar experimenter who suddenly establishes eye contact in a playful interaction (peekaboo). Video footage synchronously recorded from the perspective of the marmoset and the experimenter showed that the monkeys consistently alternated between eye contact and head-gaze aversion, and that these responses were often preceded by head-cocking. We hypothesize that this behavioral strategy helps marmosets to temporarily disengage from emotionally overwhelming social stimulation due to sight of another individual's face, in order to prepare for a new round of affiliative face-to-face interactions.

Are expression aftereffects fully explained by tilt adaptation?

Facial expressions are used as critical social cues in everyday life. Adaptation to expressions causes expression aftereffects. These aftereffects are thought to reflect the operation of face-selective neural mechanisms, and are used by researchers to investigate the nature of those mechanisms. However, recent evidence suggests that expression aftereffects could be at least partially explained by the inheritance of lower-level tilt adaptation through the visual hierarchy. We investigated whether expression aftereffects could be entirely explained by tilt adaptation. Participants completed an expression adaptation task in which we controlled for the influence of tilt by changing the orientation of the adaptor relative to the test stimuli. Although tilt adaptation appeared to make some contribution to the expression aftereffect, robust expression aftereffects still remained after minimizing tilt inheritance, indicating that expression aftereffects cannot be fully explained by tilt adaptation. There was also significant reduction in the expression aftereffects after inverting the adapting face, providing evidence that face-selective processing is involved in these aftereffects.