Neural representations of Groups and Stereotypes using fMRI repetition suppression

Categorizing people in groups and associating them with stereotypical behavior is an integral part of human social understanding and interaction. This study investigates where knowledge on social groups and their stereotypes is represented in the brain. We presented participants with two sentences describing a group member (e.g. the police officer) performing a behavior believed to be stereotypical of the group (e.g. makes an arrest, i.e. authoritative), and asked them to rate the degree to which the behavior was typical of the group. Our critical manipulation was the repetition of this information across the two sentences: Either both the group and the stereotype implied by the behavior was repeated, only the group was repeated, only the stereotype implied by the behavior, or neither. Results showed robust suppression of hemodynamic activation from the first to second sentence in the medial prefrontal cortex in response to the repetition of the stereotype implied in the behavior, but only when groups were different. This finding suggests that the neural representation of stereotypes is located in this area, and this is in line with similar repetition suppression research showing trait representation in this area. A suppression effect for the repetition of groups was observed in the posterior cingulate cortex, regardless of whether stereotypes were repeated or not. This finding suggests that the neural representation of groups is located in this area. Because this location is unexpected, we discuss several suggestions for future research to confirm this finding.