Camera-to-subject distance affects face configuration and perceived identity

Face identification is reliable for viewers who are familiar with the face, and unreliable for viewers who are not. One account of this contrast is that people become good at recognising a face by learning its configuration-the specific pattern of feature-to-feature measurements. In practice, these measurements differ across photos of the same face because objects appear more flat or convex depending on their distance from the camera. Here we connect this optical understanding to face configuration and identification accuracy. Changing camera-to-subject distance (0.32m versus 2.70m) impaired perceptual matching of unfamiliar faces, even though the images were presented at the same size. Familiar face matching was accurate across conditions. Reinstating valid distance cues mitigated the performance cost, suggesting that perceptual constancy compensates for distance-related changes in optical face shape. Acknowledging these distance effects could reduce identification errors in applied settings such as passport control

Face Recognition in Challenging Situations

A great deal of previous research has demonstrated that face recognition is unreliable for unfamiliar faces and reliable for familiar faces. However, such findings typically came from tasks that used ‘cooperative’ images, where there was no deliberate attempt to alter apparent identity. In applied settings, images are often far more challenging in nature. For example multiple images of the same identity may appear to be different identities, due to either incidental changes in appearance (such as age or style related change, or differences in images capture) or deliberate changes (evading own identity through disguise). At the same time, images of different identities may look like the same person, due to either incidental changes (natural similarities in appearance), or deliberate changes (attempts to impersonate someone else, such as in the case of identity fraud). Thus, past studies may have underestimated the applied problem. In this thesis I examine face recognition performance for these challenging image scenarios and test whether the familiarity advantage extends to these situations. I found that face recognition was indeed even poorer for challenging images than previously found using cooperative images. Familiar viewers were still better than unfamiliar viewers, yet familiarity did not bring performance to ceiling level for challenging images as it had done in the cooperative tasks in the past. I investigated several ways of improving performance, including image manipulations, exploiting perceptual constancy, crowd analysis of identity judgments, and viewing by super-recognisers. This thesis provides interesting insights into theory regarding what it is that familiar viewers are learning when they are becoming familiar with a face. It also has important practical implications; both for improving performance in challenging situations and for understanding deliberate disguise

The use of 3D information in face recognition

Effects of shading in face recognition have often alluded to 3D shape processing. However, research to date has failed to demonstrate any use of important 3D information. Stereopsis adds no advantage in face encoding [Liu, C. H., Ward, J., & Young, A. W. (in press). Transfer between 2D and 3D representations of faces. Visual Cognition], and perspective transformation impairs rather than assists recognition performance [Liu, C. H. (2003). Is face recognition in pictures affected by the center of projection? In IEEE international workshop on analysis and modeling of faces and gestures (pp. 53-59). Nice, France: IEEE Computer Society] . Although evidence tends to rule out involvement of 3D information in face processing, it remains possible that the usefulness of this information depends on certain combinations of cues. We tested this hypothesis in a recognition task, where face stimuli with several levels of perspective transformation were either presented in stereo or without stereo. We found that even at a moderate level of perspective transformation where training and test faces were separated by just 30 cm, the stereo condition produced better performance. This provides the first evidence that stereo information can facilitate face recognition. We conclude that 3D information plays a role in face processing but only when certain types of 3D cues are properly combined. © 2005 Elsevier Ltd. All rights reserved