Reinforcement history and the extinction of conditioned salivary response

Extinction of a classically conditioned salivary response in dogs was investigated in relation to different magnitudes of food US and to different percentages of food-reinforced trials during acquisition. The larger magnitudes and percentages were followed by persistently greater conditioned salivation on the 1st trials of extinction days as well as on later trials in the case of the magnitude comparison. Partially reinforced Ss decreased less within-days than continuously reinforced Ss, thereby producing a degree of "partial reinforcement effect." The differences between these results and those obtained in instrumental reward extinction are discussed in terms of possible difference in the decremental processes.