Asymmetric dependencies in perceiving identity and emotion: Experiments with morphed faces

We investigated whether an asymmetric relationship between the perception o f identity and emotional expressions in faces (Schweinberger & Soukup, 1998 ) may be related to differences in the relative processing speed of identit y and expression information. Stimulus faces were morphed across identity w ithin a given emotional expression, or were morphed across emotion within a given identity. In Experiment 1, consistent classifications of these image s were demonstrated across a wide range of morphing, with only a relatively narrow category boundary. At the same time, classification reaction times (RTs) reflected the increased perceptual difficulty of the morphed images. In Experiment 2, we investigated the effects of variations in the irrelevan t dimension on judgments of faces with respect to a relevant dimension, usi ng a Garner-type speeded classification task. RTs for expression classifica tions were strongly influenced by irrelevant identity information. In contr ast, RTs for identity classifications were unaffected by irrelevant express ion information, and this held even for stimuli which identity was more dif ficult and slower to discriminate than expression. This suggests that diffe rences in processing speed cannot account for the asymmetric relationship b etween identity and emotion perception. Theoretical accounts proposing inde pendence of identity and emotion perception are discussed in the light of t hese findings.