Abstract
5 groups of 8 rats each received 5 training trials in a straight alley in order to assess the predictions from the stimulus-aftereffect hypothesis and from the nonconditioning theory of frustration concerning the small-trial PRE. 1N-R and 2N-R transitions were factorially combined with reinforcement percentages of 40 and 60. The 5th group was continuously reinforced for control. The PRE was clearly demonstrated, and the resistance to extinction was an increasing function of the number of N-R transitions. The 40% groups did not differ from the 60% groups. The results were interpreted as supporting the stimulus-aftereffect hypothesis rather than the theory of primary unconditioned frustration.
