Two approaches to the study of response strength may be distinguished; one using the rate of responding as a measure of strength, and another using resistance of responding to change brought about by a new variable. Research in either tradition generally use quite similar methods of bringing about behavior change.The present group of studies aimed to investigate implications of the resistance-to-change findings for the response-reinforcer relationships studied in research on the Law of Effect. Experiment 1 showed that if reinforcers of different duration maintain responses in different multiple-schedule components, responding maintained by long reinforcers changes less when response-independent reinforcers are presented during an intervening blackout period.This greater resistance to change is still evident in steady-state responding, achieved after many sessions of training. Experiment 2 also used reinforcers of different duration in two multiple-schedule components. Instead of using reinforcers in blackout, responding was varied by changing the frequency of reinforcement maintaining responding in the two components. This time, the extent of response-rate change did not depend on the duration of the reinforcers maintaining responding. Response rates showed similar proportional changes in the two components when the rates of unequal-duration reinforcers were varied. Experiment 3 sought to determine whether the response rate ratio sensitivity to reinforcer rate ratios was greater when short duration reinforcers maintained responding than when long reinforcers were used.Two identical series of reinforcer rate manipulations were used with two-component multiple schedules. A long reinforcer duration was used for both components in one series, and a short reinforcer duration was used in the other. Sensitivity to reinforcer rate ratios was essentially the same in the two series. The results of the three experiments show that the usual resistance-to-change findings may only occur when behavior change is brought about by a variable which is remote from the schedules maintaining responding.This inconsistency between the results of Experiment 1 and those of Experiments 2 and 3 may be due to differences in resistance to change being counterbalanced by unequal application of the assessment technique. Integration of the two approaches studying response strength is difficult because research has not fully investigated the possibility that aspects of the reinforcer situation may combine with one another.