FI length and performance of an FI FR chain schedule of reinforcement.

In a chained FI FR schedule, manipulating the length of the FI component produced changes confined almost entirely to the FI performance; increasing the interval length increased the total number of responses emitted per reinforcement. The configuration of the fixed-interval scallop was clearly modified as the interval length was increased, with the larger intervals becoming flatter (i.e., a larger proportion of the total responses earlier in an interval). Measurement of the postreinforcement pause is suggested as a possible indicator of fixed-interval scalloping.