Allocating time to two or more response classes so all local reinforcement rates are equal. For example, assume a pigeon whose pecks in a changeover-key procedure are maintained by concurrent VI 20-s VI 60-s schedules. In an hour, the former provides about 180 reinforcers and the latter about 60, but if the pigeon allocates 45 minutes to the VI 20-s schedule and 15 minutes to the VI 60-s schedule both local 'reinforcement rates will equal about 4 per rrunute (180 in 45 n-dnutes and 60 in 15 minutes).