Avatars vs Point-light Faces: Movement Matching is Better Without a Face

Abstract

Facial movement may provide cues to identity, by supporting extraction of shape information from the face, or via idiosyncratic individual motion patterns. Although previous studies have examined whether recognition of familiar or unfamiliar faces can benefit from motion, it is rare that the two are compared directly. Furthermore, they have generally used different methods and stimuli, leading to difficulty in determining whether movement benefits familiar and unfamiliar faces to the same extent. We present two studies assessing the movement advantage in faces, by using facial point-light-displays (PLDs) or shape-averaged avatars. Experiment 1 tested the matching of famous and unfamiliar faces in a same/different task, using the same stimulus type within each pair. Matching performance was better for PLDs than for avatars, and for familiar compared to unfamiliar faces. There was a significant advantage for matching moving images compared to static images for both familiar and unfamiliar faces, although this was larger for unfamiliar faces. Experiment 2 also used a same/different task, but participants attempted to match non-degraded images of famous and unfamiliar faces to PLDs or avatars. Overall performance in Experiment 2 was lower than Experiment 1. Once again, matching performance was better for PLDs compared to avatars, and familiar compared to unfamiliar faces. A movement advantage was present for unfamiliar faces only. The performance differences between PLDs and avatars, and between Experiments 1 and 2, indicate that the benefit derived from viewing a face in motion depends on the type of information contained in stimuli and the task. Although participants are capable of generalizing between movement sequences in a matching task, it is more difficult when the format of the sequences is varied. Overall, these results suggest that movement can provide a useful cue to identity, particularly for unfamiliar faces.