The duration and course of the reaction decrement and the influence of reward.

Abstract

Various existing theories suggest that the immediate effect of reward is to decrease variability. Existing empirical evidence suggests that the reaction decrement of a single reac-tion is relatively short. Hull''s and Glanzer''s formulations of reactive inhibition and stimulus satiation predict the decay of the reaction decrement with time to be a simple negative expo-nential decay function. It is maintained here that reward can have an initial effect of increasing variability, that a reaction decrement can last much longer than previously expected, and that the course of dissipation of the reaction decrement can be sustained over a period before undergoing a fairly abrupt drop. Alternation behavior was examined in a T-maze with 126 animals, all thirsty but half of them reinforced with water in either arm of the maze on all trials, half never reinforced. The animals in each reinforcement condition were divided into three groups , each group tested seven times on seven different days at seven different delay intervals. Thus 21 different delay intervals were tested ranging from an operational delay of 15 seconds to four hours and sixteen minutes with 21 animals tested each delay in-terval. 1. The rewarded group alternated significantly more than the unrewarded group, even after a delay sufficient for both groups often to repeat their original responses. The latter find-ing, contrary to all theories, is considered an artifact absent with longer delays. 2. The alternation effect (and thus by impli-cation the reaction decrement from the first reaction) was still evident after approximately 90 minutes, considerably longer than expected from previous data. 3. The form of the curve of dis-sipation of the reaction decrement was not the simple exponential decay function expected from passive dissipation of the residual effects of the reaction, but showed a rather steadily maintained decrement followed by a rather abrupt drop to a point below the 50% alternation level.