PAVLOVIAN PERFORMANCE OF RATS FOLLOWING UNEXPECTED REWARD OMISSIONS

Instrumental performance is usually facilitated following the unexpected omission of a reward. According to frustration theory, this effect reflects the general activating properties of primary frustration. Results based on the double runway procedure and Skinner box analogs are ambiguous because designs usually failed to match experimental and control conditions in the number and distribution of rewards. In Experiment 1, evidence of response activation was found in a Pavlovian situation with rats under equal conditions of reinforcement across groups. Autoshaped lever-contact was the target response and food pellets were the reward. In Experiment 2, response activation was eliminated by an increase in the interval between food omission and the opportunity to respond. In Experiment 3, response facilitation was obtained when the omitted reward was a sugar solution. The results of Experiment 4 indicated that response activation can be obtained with an unexpected reduction in reward magnitude (from 5 to I pellet). Both between- and within-group controls were used in these experiments to eliminate a Variety of potential accounts, including demotivation, competing responses, and stimulus generalization decrement. These results are consistent with an account of the response facilitation that follows unexpected reward omissions in terms of generalized activation. (C) 1995 Academic Press, Inc.