Abstract
Matching the identities of unfamiliar faces is heavily influenced by variations in their images. Changes to viewpoint and lighting direction during face perception are commonplace across yaw and pitch axes and can result in dramatic image differences. We report two experiments that, for the first time, factorially investigate the combined effects of lighting and view angle on matching performance for unfamiliar faces. The use of three-dimensional head models allowed control of both lighting and viewpoint. We found viewpoint effects in the yaw axis with little to no effect of lighting. However, for rotations about the pitch axis, there were both viewpoint and lighting effects and these interacted where lighting effects were found only for front views and views from below. The pattern of effects was similar regardless of whether view variation occurred as a result of head (Experiment 1) or camera (Experiment 2) suggesting that face matching is not purely image based. Along with face inversion effects in Experiment 1, the results of this study suggest that face perception is based on shape and surface information and draws on implicit knowledge of upright faces and ecological (top) lighting conditions.
Highlights
The image of a face is determined by its shape and reflectance and by the directions from which it is viewed and lit
If the inversion effect is taken as an indicator of visual processes specific to upright faces (e.g., Robbins & McKone, 2003; Rossion & Boremanse, 2008), this result suggests that the effects of yaw angle changes in view or lighting are not influenced by face-specific processing
When the camera was rotated to the right matching performance with front lighting was significantly more accurate than with left lighting (p 1⁄4 .02) but there was no difference between right and front lighting or between right and left lighting
Summary
The image of a face is determined by its shape and reflectance and by the directions from which it is viewed and lit. Adini, Moses, and Ullman (1997) made objective comparisons of face images rendered under various viewing conditions and demonstrated that changes in lighting accounted for greater image variance than changes in viewpoint (and that both accounted for greater image variance than changes in identity). Extrinsic factors such as viewpoint and lighting direction together with the intrinsic three-dimensional (3D) shape and surface reflectance properties of a face determine the pattern of shading and shadows, as well as the surfaces of a face that are visible (Hill & Bruce, 1996; Liu, Collin, & Chaudhuri, 2000). We investigate how viewpoint and lighting together impact the processing of this intrinsic, identity-specific face information using a sequential matching task with unfamiliar faces
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