Reinforcing the absence of fixed-ratio performance.

Pigeons received food for key pecking according to a fixed-ratio schedule, while, at the same time, food also was available for not pecking for a specified time. With a fixed ratio of 60, responding was not affected by not-pecking times of 80 or 40 seconds, and was eliminated completely at 10 seconds. With ratios of 180, pecking stopped with not-pecking times of 80 seconds or less; with ratios of 300, it stopped at 120 seconds or less. Not-responding schedules produced steady-state performance immediately following contact with the schedule. With return to the fixed-ratio schedule alone, response rate sometimes was elevated temporarily. When response-independent food presentations replaced the not-pecking schedule, response rate often was enhanced, and the ratio pattern was lost. Only the highest densities of food delivery eliminated responding, even with a fixed ratio of 300. In general, the effects corresponded to those of punishment, except that contrast had appeared both during and after punishment, and now appeared only after the response elimination procedure was suspended.