An Analysis of the Effects of Delay of Reinforcement and Momentary Probabilities of Reinforcement on Interval Schedule Performance

In two experiments pigeons were exposed to VI and FI schedules and viii schedules approximating both VI and FI schedules. In experiment I, the probabilities of the VI and FI components in a Mixed FI VI schedule were manipulated to create schedule contingencies approximating simple VI or FI. In experiment II, the minimum and maximum inter-reinforcement intervals were manipulated to create schedule contingencies approximating simple VI or FI. The major finding of both of these experiments was that maximal control by the dimension of time occurred as FI contingencies were approximated. Control by any one temporal value in experiment I depended on its temporal separation from 100 seconds and the probability of reinforcement associated with 100 seconds. Control by any one temporal value in experiment II depended on its temporal separation from the minimum inter-reinforcement interval and 100 seconds. The results were discussed in terms of interval schedule control as a form of stimulus control. A third experiment was performed to examine possible relationships between the pause in FI performance and the subsequent scallop. The baseline condition was contaminated by a procedure which may have produced effects which overrode experimental manipulations. Finally, an experiment was suggested to demonstrate behavioral contrast along a temporal dimension. The argument that interval schedule control is a form of stimulus control rested on analogy and inference. A demonstration of behavioral contrast along a temporal dimension would demonstrate more directly that time is similar to other dimensions. Hence, the same principles could be used to explain schedule control as are used to explain stimulus control