Temporal distributions of responding during discrete-trial omission training in rats.

Scientists ran 60 one-minute trials with rats. If the rat did not press the lever, it got sucrose at the end of the minute. This setup is called omission training — pressing costs you the treat.

They tracked when lever presses happened across the whole session.

Lever pressing grew stronger as the session went on. The chance of a press was low early, but rose steadily minute after minute.

The rats did not stop; they escalated even though pressing canceled the reward.

Griesi-Oliveira et al. (2013) saw the opposite pattern. When a conditioned reinforcer was delayed, lever pressing dropped. Here, no reinforcer was ever given for pressing, yet pressing climbed. The difference is timing: delay weakens behavior, while omission creates its own momentum.

Keller (1966) showed that even a two-second delay can produce superstitious bar pressing. The 1979 study extends this idea — superstitious-like pressing can keep growing across an entire session when rewards are withheld for responding.

KELLEHEBERRYMAELLIOTT et al. (1962) found that pigeons worked for stimuli that signaled food, not food itself. Together these papers show that reinforcer timing and signaling, not just the food, shape the pace of responding.

Omission training can accidentally strengthen the very behavior you want to cut. If you withhold reinforcement hoping a child will stop an unwanted response, watch the clock. Early quiet can turn into late burst. Track responding minute-by-minute during extinction or omission phases. If you see an upward slope, add an alternative task that earns reinforcement before the unwanted behavior snowballs.