Religious labels and food preferences, but not country of origin, support opposing face aftereffects

Face templates can be experimentally manipulated, and category-contingent aftereffects suggest discrete templates across social groups. We tested whether 1) explicit religious labels, 2) food preferences, and 3) country of origin would support religion-contingent aftereffects across Christians and Muslims face sets. While viewing face images, ninety-three participants heard audio that stated either 1) a character's religious identity, 2) preferred food, or 3) country of origin. Participants viewed contracted Christian faces and expanded Muslim faces during the training phase. To measure adaptation, before and after the training phases, participants selected the face out of a pair of expanded and contracted Christian or Muslim faces that they found more attractive. Contingent aftereffects were found in the religious explicit (t(30) = 2.49, p = 0.02, Cohen's d = 0.58) and food conditions (t(30) = -3.77, p < 0.01, Cohen's d = -0.82), but not the country condition (t(30) = 1.64, p = 0.11, Cohen's d = 0.31). This suggests that religious labels and food preferences create socially meaningful groups, but country of origin does not. This is evidence of an impact of social categorization on visual processing.