"Symbolic Communication" Between Two Pigeons (Columba livid) Without Unconditioned Reinforcement

This study addressed the question: Can nonhuman organisms be conditioned to respond discriminatively to abstract features of their environments without unconditioned reinforcement? It demonstrated that two pigeons can be conditioned to maintain an interaction in which one pigeon has access to a discriminative stimulus that the other needs in order to emit a reinforced response, and responds in the absence of deprivation, aversive stimulation, and unconditioned reinforcement. This finding adds to the class of variables heretofore demonstrated to maintain "symbolic repertoires" and highlights a fresh paradigm for conditioning other spontaneous interactions between and within nonhuman species. The importance of social stimuli in such interchanges is demonstrated.