The phylogenetic roots of cognitive dissonance.

We presented 7 Old World monkeys (Japanese macaques [Macaca fuscata], gray-cheeked mangabey [Lophocebus albigena], rhesus macaques [Macaca mulatta], bonnet macaque [Macaca radiate], and olive baboon [Papio anubis]), 3 chimpanzees (Pan troglodytes), 6 members of the parrot (Psittacinae) family, and 4 American black bears (Ursus americanus) with a cognitive dissonance paradigm modeled after Egan, Santos, and Bloom (2007). In experimental trials, subjects were given choices between 2 equally preferred food items and then presented with the unchosen option and a novel, equally preferred food item. In control trials, subjects were presented with 1 accessible and 1 inaccessible option from another triad of equally preferred food items. They were then presented with the previously inaccessible item and a novel member of that triad. Subjects, as a whole, did not prefer the novel item in experimental or control trials. However, there was a tendency toward a subject by condition interaction. When analyzed by primate versus nonprimate categories, only primates preferred the novel item in experimental but not control trials, indicating that they resolved cognitive dissonance by devaluing the unchosen option only when an option was derogated by their own free choice. This finding suggests that this phenomenon might exist within but not outside of the primate order.