Neural adaptation to faces reveals racial outgroup homogeneity effects in early perception

Abstract

Significance The tendency to view members of social outgroups as interchangeable has long been considered a core component of intergroup bias and a precursor to stereotyping and discrimination. However, the early perceptual nature of these intergroup biases is poorly understood. Here, we used a functional MRI adaptation paradigm to assess how face-selective brain regions respond to variation in physical similarity among racial ingroup (White) and outgroup (Black) faces. We conclude that differences emerge in the different tuning properties of early face-selective cortex for racial ingroup and outgroup faces and mirror behavioral differences in memory and perception of racial ingroup versus outgroup faces. These results suggest that outgroup deindividuation emerges at some of the earliest stages of perception. A hallmark of intergroup biases is the tendency to individuate members of one’s own group but process members of other groups categorically. While the consequences of these biases for stereotyping and discrimination are well-documented, their early perceptual underpinnings remain less understood. Here, we investigated the neural mechanisms of this effect by testing whether high-level visual cortex is differentially tuned in its sensitivity to variation in own-race versus other-race faces. Using a functional MRI adaptation paradigm, we measured White participants’ habituation to blocks of White and Black faces that parametrically varied in their groupwise similarity. Participants showed a greater tendency to individuate own-race faces in perception, showing both greater release from adaptation to unique identities and increased sensitivity in the adaptation response to physical difference among faces. These group differences emerge in the tuning of early face-selective cortex and mirror behavioral differences in the memory and perception of own- versus other-race faces. Our results suggest that biases for other-race faces emerge at some of the earliest stages of sensory perception.