Kemp, Richard Ian; (1995) Face perception: Sensitivity to feature displacement in normal, negative and inverted images. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Previous research on face recognition has focused mainly on the factors that affect our memory for faces. Two such factors are image inversion and negation which have been shown to affect our memory for faces more than for other objects. This has led to the suggestion that face recognition utilises special processes not involved in the recognition of other objects. This thesis investigates the perception of faces and seeks to establish whether face perception is also affected by these image manipulations and whether there is any evidence of face-specific perceptual processing. A procedure is developed in which subjects are asked to identify which of two images has been modified through the introduction of a small displacement to the location of the features. It is demonstrated that subjects are more sensitive to feature displacement in normal than in either inverted or negated facial images, but that these transformations do not affect the perception of non-facial images. Further experiments seek to identify the causes of these effects by systematically replacing the facial features with geometric shapes and by developing novel colour transformations. It is suggested that the inversion and negation effects could be considered as examples of the object-superiority effect whereby the presence of a coherent context allows for the more accurate perception of the components of an image. This suggestion is supported by the demonstration that subjects are more sensitive to feature displacement in face than non-face images, and that the effects of the negation and inversion transformations is to reduce the level of performance to that achieved with non-face images. These concepts are incorporated into a provisional model of face perception in which prior knowledge of the structure of the human face allows for a deeper, and hence more accurate processing of the image.

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