Do birds experience sensory pleasure?

Abstract

To answer the question of whether sensory pleasure exists in birds, I trained an African-gray parrot (Psittacus erythacus) named Aristote to speak. Stage 1 of the study consisted in gaining Aristote's affection. In Stage 2 Aristote was taught to speak, following Irene Pepperberg's triangular method: another person and I would talk together and look at Aristote only when it used understandable French words. Thus Aristote learned to say a few words for obtaining toys or getting my attention; e.g. "donne bouchon" (give cork) or "donne gratte" (give scratch/ tickle), with the appropriate reward. In Stage 3, the word bon (good) was added to the short list of words used by Aristote. I said "bon" when giving Aristote the stimuli it requested and which would, presumably, be pleasurable; e.g. gratte bon. Aristote started to use short sentences such as "yaourt bon" (good yogurt). Eventually, Aristote transferred the word bon to new stimuli such as raisin (grape), an association I myself had never made. Such a use of vocabulary, and moreover its transfer, likely shows that this bird experienced sensory pleasure.