Dissociating retina- and face-centered reference frames of human face recognition.

Face identity recognition is a core function of the human brain, predominantly driven by horizontally-oriented facial cues. The reference frame of the (horizontal) information driving human face identification has not been systematically addressed. Therefore, a core characteristic of human face identity recognition remains undefined.The reference frame of the horizontal information driving face identification may be centered either on the observer’s retina (i.e. retina-centered), or the face stimulus (i.e. face-centered). To disentangle these alternatives, 42 young adults performed identity recognition of famous faces. Stimuli were filtered to restrict content to narrow orientation bands (i.e., from 0° to 150°, in 30°-steps), and presented either upright, rotated by ±45°, or by ±90° away from upright. If the horizontal face identity information is defined along retinal coordinates, the peak of identification performance should shift away from horizontal (90°) as a function of rotation angle (peak shift from 90° to 135° for a +45° rotation). In contrast, a reference frame centered on the face identity recognition performance should stay tuned to the horizontal irrespective of rotation angle.Overall performance significantly decreased when faces were rotated by ±90° compared to other rotation angles. Recognition performance peaked in the horizontal range of the face stimulus regardless of rotation angle. However, the advantage of the horizontal over the vertical range decreased significantly for ±90° compared to upright and ±45° rotations suggesting partial dependence on the retina-centered reference frame. These results indicate that the horizontal information driving human face-specialized identity recognition is defined within the reference frame of the face-image.