Stimulus Factors Affecting the Categorization of Faces and Scrambled Faces

Three experiments are reported which investigate the categorisation of faces and scrambled faces in a face/scrambled face decision task. Three kinds of stimuli were presented in upright and inverted orientations; faces, highly scrambled faces (all features out of position) and moderately scrambled faces (two features out of position). Experiment 1 demonstrated that faces and highly scrambled faces are categorised equally quickly and both types of stimulus were categorised faster than moderately scrambled faces. These results held for both upright and inverted presentations. It is argued that for both upright and inverted presentations, faces are categorised by being matched in parallel to a stored mental representation of a face. In contrast scrambled faces are categorised following a serial search of facial features which is probably self-terminating. Experiment 2 demonstrates that the results of Experiment 1 hold when facial features are replaced by other objects which retain the same global shape as facial features and suggest that faces are categorised using a coarsely coded visual description. Experiment 3 demonstrates the importance of stimulus outline on the categorisation of both moderately and highly scrambled faces but not real faces. The results are discussed in terms of the stimulus information used, and the effect of inversion, on face categorisation.