Some limitations on behavioral contrast and induction during successive discrimination.

A pigeon's rate of pecking on a red key, reinforced at a constant frequency, may be changed by increasing or decreasing the frequency of reinforcement of pecking on a successively presented green key. The changes in the rate of pecking on red, called interactions, are of two types: contrast, in which the changes in the rates of pecking on the two colors are in opposite directions; and, induction, in which the changes in the rates are in the same direction. In previous data, a change in the frequency of reinforcement associated with the green key produced a corresponding change in the rate of pecking the green key and an opposite change (contrast) in the rate of pecking on the red key. The present data suggest that the magnitude of contrast is very small if pecking on the red key is reinforced at a high enough frequency (about 40 reinforcements per hr in the present experiment). Also, given that interactions occur, induction rather than contrast may result from small changes in a low frequency of reinforcement associated with green.