The role of the peck-food contingency on fixed-interval schedules.

Whitehead et al. (1975) worked with pigeons on fixed-interval schedules. They asked: does the bird still have to peck to get food?

In one condition the peck produced food. In others the food came no matter what. The team watched how rate and pattern changed.

When the peck-food link was cut, the pretty scallop flattened. Birds pecked less and the pause after food grew longer.

The longer the interval, the bigger the drop. At short intervals birds still pecked a little. At long intervals they almost stopped.

Byrd (1972) saw the same flattening, but used partial food instead of no food. Even 7% of intervals paid kept the scallop alive. The two studies line up: weaker contingency means weaker pattern.

Kono (2017) adds space to the story. Longer FI schedules made pigeons drift away from the center key and peck in new spots. E et al. showed time matters; Kono shows place matters too.

Okouchi (2003) flips the lens. He gave pigeons a history of fast or slow pay before the FI. That past rate, not the current peck, set their speed. E et al. locked the moment; Hiroto shows baggage from yesterday still drives today.

Your client’s response may look like ‘scalloping,’ but check the contingency. If the reinforcer arrives no matter what, the pattern will flatten and rate will drop, especially during long waits. Keep the response-reinforcer link tight, or shorten the interval, to protect the rhythm you want.