The motivational bases of the social reinforcement in human-dog relations were examined. In experiment I, performed on seven dogs, it was found that dogs were able to learn and sustain the natural responses of sitting, paw extension, and lying prostrate to conditional stimuli in the form of vocal commands reinforced only by social rewards given by the experimenter, such as petting and vocal encouragement. Overtraining did not produce deterioration of performance but, on the contrary, the continual decrease of latencies. It was evidenced that tactile stimulation plays an important role in social reward. In experiment II, instrumental responses to the auditory conditional stimuli were elaborated in two groups of dogs. The first group (nine dogs) was reinforced by food, and the second group (eight dogs) was reinforced exclusively by petting. A similar course of learning and level of performance during overtraining sessions in both groups indicated that petting serves as a good reinforcement, with rewarding value comparable to that of food reinforcement. It is suggested that a strong rewarding effect of pleasurable sensory stimuli occurs in the formation of the bond between dog and human and in the learning of different tasks.
