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

Abstract

We investigated whether an asymmetric relationship between the perception of identity and emotional expressions in faces (Schweinberger & Soukup, 1998) may be related to differences in the relative processing speed of identity and expression information. Stimulus faces were morphed across identity within a given emotional expression, or were morphed across emotion within a given identity. In Experiment 1, consistent classifications of these images 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 irrelevant dimension on judgments of faces with respect to a relevant dimension, using a Garner-type speeded classification task. RTs for expression classifications were strongly influenced by irrelevant identity information. In contrast, RTs for identity classifications were unaffected by irrelevant expression information, and this held even for stimuli in which identity was more difficult and slower to discriminate than expression. This suggests that differences in processing speed cannot account for the asymmetric relationship between identity and emotion perception. Theoretical accounts proposing independence of identity and emotion perception are discussed in the light of these findings,

Garner interference reveals dependencies between emotional expression and gaze in face perception.

“…Our goal was to control for any identity-related effects on facial expression processing (e.g., Schweinberger et al, 1999) and to make our results comparable to those of Ganel et al (2005), who also used singleidentity exemplars. However, there is a possibility that the use of one identity per experiment may have encouraged strategies that were picture specific and not necessarily related to emotion processing per se.…”

“…According to a speed-of-processing account (e.g., Atkinson et al, 2005;Schweinberger et al, 1999), mismatches in discriminability would cause asymmetric interference patterns because the more discriminable dimension (i.e., emotional facial expressions) is computed before the less discriminable dimension (i.e., gaze direction) has been fully processed. This would explain why our results differed from Ganel et al (2005).…”

“…Existing studies suggest that the interaction between the variant and invariant processing streams tends to be asymmetric. Whereas identity and gender judgments are not affected by variations in facial expression and speech, expression and speech judgments are affected by variations in identity and gender (Atkinson et al, 2005;Schweinberger et al, 1999;Schweinberger & Soukoup, 1998). Finally, Ganel et al (2005) provided recent evidence that within the dynamic stream, interactions between gaze and expression processing can be manipulated by inversion and discriminabilty.…”

“…Only one identity was utilized for two reasons. First, previous studies have established that facial identity modulates the perception of facial expression (Schweinberger et al, 1999). Second, we wanted our protocol to be comparable to that of Ganel et al (2005) who also used one identity.…”

“…The original paradigm also included a correlated or redundant condition that has since been found to violate several assumptions and, hence, is not suitable for the determination of separability/ integrality (see Ashby & Maddox, 1994;Maddox & Ashby, 1996, for a discussion of this issue). The Garner paradigm has been used to study the interdependence of various aspects of face processing, including the relationship between gender and identity (Ganel & Goshen-Gottstein, 2002), gender and emotional expression (Atkinson, Tipples, Burt, & Young, 2005;Le Gal & Bruce, 2002), identity and expression (Baudouin, Martin, Tiberghien, Verlut, & Franck, 2002;Schweinberger, Burton, & Kelly, 1999;Schweinberger & Soukoup, 1998), identity and speech information (Schweinberger et al, 1999;Schweinberger & Soukoup, 1998) and, most importantly for the present study, the relationship between gaze and expression (Ganel, Goshen-Gottstein, & Goodale, 2005).…”