Categorization of Ambiguous Human/Ape Faces: Protection of Ingroup but Not Outgroup Humanity

In two studies, we tested the hypothesis that categorization of ambiguous human/ape faces depends on group membership: people are inclined to protect ingroup humanity, but not that of the outgroup. We used as stimuli: human, ape, ambiguous human/ape faces. Ambiguous human/ape faces were generated using a computerized morphing procedure. Participants categorized stimuli as human or ape. Two conditions were introduced: in the ingroup condition, participants were informed that human exemplars were ingroup members, in the outgroup condition that they were outgroup members. We expected participants, in an effort to protect ingroup humanity, to categorize ambiguous stimuli as ape more often in the ingroup than outgroup condition. Predictions were confirmed. Results are discussed in the context of infrahumanization theory.