Effects of Geometric Distortions on Face-Recognition Performance

Abstract

The importance of ‘configural’ processing for face recognition is now well established, but it remains unclear precisely what it entails. Through four experiments we attempted to clarify the nature of configural processing by investigating the effects of various affine transformations on the recognition of familiar faces. Experiment 1 showed that recognition was markedly impaired by inversion of faces, somewhat impaired by shearing or horizontally stretching them, but unaffected by vertical stretching of faces to twice their normal height. In experiment 2 we investigated vertical and horizontal stretching in more detail, and found no effects of either transformation. Two further experiments were performed to determine whether participants were recognising stretched faces by using configural information. Experiment 3 showed that nonglobal vertical stretching of faces (stretching either the top or the bottom half while leaving the remainder undistorted) impaired recognition, implying that configural information from the stretched part of the face was influencing the process of recognition — ie that configural processing involves global facial properties. In experiment 4 we examined the effects of Gaussian blurring on recognition of undistorted and vertically stretched faces. Faces remained recognisable even when they were both stretched and blurred, implying that participants were basing their judgments on configural information from these stimuli, rather than resorting to some strategy based on local featural details. The tolerance of spatial distortions in human face recognition suggests that the configural information used as a basis for face recognition is unlikely to involve information about the absolute position of facial features relative to each other, at least not in any simple way

Effect of Vertical Stretching on the Extraction of Mean Identity From Faces

“…This is consistent with previous research demonstrating that geometric distortions, such as stretching, do not impair recognition accuracy (Hole et al, 2002;Sandford et al, 2013). These previous studies used famous/nonfamous judgment tasks.…”

“…Hole et al, 2002). However face recognition is impaired by other transformations, such as non-global face distortions (Hole et al, 2002), photographic negation (Galper, 1970) and inversion (Yin, 1970), and also by changes in pose and expression. Future research could investigate how these transformations affect the set averaging process.…”

Whole-face procedures for recovering facial images from memory

“…When applied to photographs, by doubling the height, Hole, George, Eaves and Rasek (2002) found that recognition accuracy of familiar (celebrity) faces did not decrease relative to unaltered images (although reaction times were slower in one of their four experiments). However, as described in Astbury (2011), doubling height or width of familiar-face (celebrity) composites substantially improved an observer's ability to correctly name the face.…”

“…Relative to looking at the face front-on, this 'perceptual' stretch about doubled correct naming, from 17% to 36%. Hole et al (2002) argued that, for photographs of faces, an observer's cognitive system may be normalizing a stretched face prior to recognition, to fit with how a face usually appears, or that the memory itself may be altered to accommodate the transformation, a 'deformable template' theory. More-recent research by the first author (unpublished) has found that the null effect of stretching extends to unfamiliar-face recognition, which argues for the former case: normalisation of an incoming face not deformation of memory.…”

Robust representations for face recognition: The power of averages

“…Furthermore, some studies of human face recognition have shown it to be highly tolerant of certain manipulations of the shape. For example, Hole, George, Eaves & Rasek (2002) demonstrated that familiar face recognition was completely unaffected by distorting the aspect ratio of photographs by up to 2:1, vertical to horizontal. On the other hand, research on the caricature effect suggests that manipulations of shape which emphasise idiosyncratic characteristics can improve identification (e.g., Rhodes, 1996).…”