Positive behavioral contrast when pigeons press treadles during multiple schedules.

Pigeons pressed a treadle for food on two schedules that alternated every few minutes.

One schedule always paid off every 15 seconds. The other schedule either also paid every 15 seconds or never paid at all.

The birds lived in a box. A light color told them which schedule was active.

When the second schedule switched to no-pay, birds sped up on the still-paying schedule.

This jump is called positive behavioral contrast. It shows the response form does not have to be a key peck to get the effect.

McSweeney (1975) saw the same speed-up with concurrent VI schedules, so the effect is not tied to one procedure.

Whalen et al. (1979) later got the same jump in three-month-old babies, proving the rule works across species.

Varley et al. (1980) used the same treadle press and found peak shift, showing this response is handy for many basic phenomena.

If you run multiple schedules with clients, expect faster responding in the rich component when the poor one gets poorer. The effect holds for any movable operandum, not just finger taps. Watch for accidental contrast when you thin reinforcement in one setting while keeping it dense in another.