FACIAL EXPRESSION MEGAMIX - TESTS OF DIMENSIONAL AND CATEGORY ACCOUNTS OF EMOTION RECOGNITION

We report four experiments investigating the perception of photographi c quality continua of interpolated ('morphed') facial expressions deri ved from prototypes of the 6 emotions in the Ekman and Friesen (1976) series (happiness, surprise, fear, sadness, disgust and anger). In Exp eriment 1, morphed images made from all possible pairwise combinations of expressions were presented in random order; subjects identified th ese as belonging to distinct expression categories corresponding to th e prototypes at each end of the relevant continuum, This result was re plicated in Experiment 2, which also included morphs made from a proto type with a neutral expression, and allowed 'neutral' as a response ca tegory. These findings are inconsistent with the view that facial expr essions are recognised by locating them along two underlying dimension s, since such a View predicts that at least some transitions between c ategories should involve neutral regions or,identification as a differ ent emotion. Instead, they suggest that facial expressions of basic em otions are recognised by their fit to discrete categories. Experiment 3 used continua involving 6 emotions to demonstrate best discriminatio n of pairs of stimuli falling across category boundaries; this provide s further evidence of categorical perception of facial expressions of emotion. However, in both Experiment 1 and Experiment 2, reaction time data showed that increasing distance from the prototype had a definit e cost on ability to identify emotion in the resulting morphed face. M oreover, Experiment 4 showed that subjects had some insight into which emotions were blended to create specific morphed images. Hence, categ orical perception effects were found even though subjects were sensiti ve to physical properties of these morphed facial expressions. We sugg est that rapid classification of prototypes and better across boundary discriminability reflect the underlying organisation of human categor isation abilities.