Abstract
Over 50 years of research has demonstrated that orientation dramatically affects the visual processing of faces; across a wide variety of perception and memory tasks, observers show markedly worse performance when faces are presented upside-down compared to upright. However, the meaning of orientation (i.e. what counts as upright) must be established in relation to a particular reference frame. In most experiments, several reference frames are conflated: upright faces are upright with respect to the participant's retinal frame, but also with respect to environmental frames such as the layout of the experiment room and the directional pull of gravity. Here we ask: in relation to which reference frame(s) does the face inversion effect occur? We developed a novel, simple method for investigating potentially independent effects of retinal and environmental reference frames in face perception. Participants performed one of two face-processing tasks as they lay horizontally, thereby disassociating the retinal and environmental orientation of the stimuli. In Study 1, participants judged the emotional expression of Mooney faces; in Study 2, participants performed an old/new recognition task on novel face images. In both studies, we found a large effect of retinal orientation on performance and a reliable (though smaller) effect of environmental orientation. Specifically, participants in Study 1 were faster and more accurate at judging emotional expressions of environmentally upright versus environmentally upside-down faces, even though faces in both conditions were rotated by 90 degrees in the retinal frame. Similarly, recognition performance in Study 2 was better for environmentally upright versus environmentally upside-down faces. In two control studies, we ruled out alternative explanations of our findings based on the design of our stimuli and the experimental apparatus. We conclude that there exists a reliable effect of environmental orientation on face processing that is revealed when retinal orientation is held constant.
This research was funded by NRSA fellowship 1F32EY018279 to N.D.