Independently delivered food decelerates fixed-ratio rates.

Following fixed-ratio baselines, the independent delivery of reinforcers was scheduled alone or concomitant with the fixed-ratio schedule for all subjects. Systematic manipulations of either the interreinforcement interval or the ratio size were also made during concomitant schedules. Response rates during the independent delivery of reinforcers did not decelerate until the subjects had been exposed for 50 or more sessions. Rates decelerated after a few sessions when the interreinforcement intervals were less than half of the original value and scheduled along with the ratio dependency. When both schedules were available, reductions in the ratio size resulted in slight deceleration of response rate when compared with the level of deceleration yielded by reductions in the independent reinforcement intervals.