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Categorical perception of morphed facial expressions.
Authors:
Calder, A.J., Young, A.W., Perrett, D.I., Etcoff, N.L. & Rowland, D.
Reference:
Visual Cognition, 3(2), 81-117
Year of publication:
1996
CBU number:
3365
Abstract:
Using computer-generated line-drawings, Etcoff and Magee (1992) found evidence of categorical perception of facial expressions. We report four experiments which replicated and extended Etcoff and Magee's findings with photographic-quality stimuli. Experiments 1 and 2 measured identification of the individual stimuli falling along particular expression continua (e.g., from happiness to sadness), and discrimination of these stimuli with an ABX task. Our identification data showed that each expression continuum was perceived as two distinct sections separated by a category boundary. From these identification data we are able to predict subjects' performance in the ABX discrimination task and to demonstrate better discrimination of cross-boundary than within-category pairs. Experiments 3 and 4 addressed two new issues arising from Etcoff and Magee's (1992) data and the results of our own Experiments 1 and 2. First, that they might reflect artefacts inherent in the use of single continua ranging between two prototypes; for example, a range effect or an anchor effect. Second, given that the ABX procedure incorporates a short-term memory load, discrimination data obtained with this task might reflect a short-term memory rather than a perceptual phenomenon. We found no support for either of these reinterpretations, and further evidence of categorical perception.