Abstract
People often fail to individuate members of social outgroups, a phenomenon known as the outgroup homogeneity effect. Here, we used fMRI repetition suppression to investigate the neural representation underlying this effect. In a pre-registered study, White human perceivers (N = 29) responded to pairs of faces depicting White or Black targets. In each pair, the second face depicted either the same target as the first face, a different target from the same race, or a scrambled face outline. We localized face-selective neural regions via an independent task, and demonstrated that neural activity in the fusiform face area distinguished different faces only when targets belonged to the perceivers’ racial ingroup (White). By contrast, face-selective cortex did not discriminate between other-race individuals. Moreover, across two studies (total N = 67) perceivers were slower to discriminate between different outgroup members and remembered them to a lesser extent. Together, these results suggest that the outgroup homogeneity effect arises when early-to-mid-level visual processing results in an erroneous overlap of representations of outgroup members.
Significance statement Researchers have repeatedly demonstrated that perceivers struggle to distinguish between different members of a racial outgroup. Here, we show in a pre-registered study that this failure arises when areas of the human brain that specifically process facial identity—most notably, the so-called “fusiform face area”—fail to detect differences between identities of members of a racial outgroup. When White perceivers viewed photos of two different Black men, the face area of their brains responded as if the two photos portrayed the same person. This effect was constrained to outgroup faces; the face area successfully distinguished faces of two different White individuals. Our results highlight the failure of basic representational mechanisms in processing individuals from other social groups.
Footnotes
The authors declare no conflicts of interest.
This work was partially supported by the Israeli Science Foundation (No. 79/18, to N.R.) and was conducted at the Harvard University Center for Brain Science, which is supported by supported by the NIH Shared Instrumentation Grant Program (No. S10OD020039).
This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license, which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.
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