An explicit religious label impacts visual adaptation to Christian and Muslim faces

Opposing aftereffects can be induced across two sets of face categories. The current literature suggests that in order to create opposing aftereffects, the two categories must (1) be perceptually distinct and (2) represent distinct meaningfully social categories. The current study was designed to test whether religion is one of the types of social categories that can support the formation of opposing aftereffects. Experiment 1 reports the creation and validation of a Christian and Muslim face set, demonstrating that the religious membership of the face images is visually identifiable. In experiment 2 we attempted to create opposing aftereffects by having adult participants fixate on Christian and Muslim faces that were expanded and contracted. Participants either heard religious membership explicit or control audio recordings. Opposing aftereffects were observed only when Christian and Muslim faces were explicitly labeled. In experiment 3, eight-year-olds were adapted to a similar paradigm, with explicit religious information provided. Opposing aftereffects were not observed. Results of these experiments suggest that for adults, religion might be the kind of meaningful social category required for the formation of opposing aftereffects, but only if religious category membership is made explicit. Eight-year-old children's understanding of religious categories may still be developing.