Some effects of fixed-interval duration on response rate in a two-component chain schedule.

Pigeons pecked on a two-part chain schedule. Part one paid on a variable-interval timer. Part two paid on a fixed-interval timer. The team made the second timer longer or shorter, or took it away completely. They counted how fast the birds pecked in the first part.

When the second fixed interval grew, pecking in the first part slowed. When the second part was removed, the first-part rate also dropped. The later requirement clearly pulled the early response rate down.

Dougan (1987) later showed the same slowdown happens if the prior interval, not the later one, is stretched. Okouchi (2003) found that past schedules set a mood: rats that had earned fast pay kept pecking faster on the new FI. Together these papers say both future and past interval lengths shape current speed.

Ley (2001) seems to disagree. After eighty-plus FI sessions, rats forgot their old fast or slow habits. The clash is timing: Kendall (1967) watched early changes, while R let the new schedule run long enough to wipe history clean. Early sessions feel the drag; extended exposure resets the clock.

SIDMAELLIOTT et al. (1962) did the same trick earlier, chaining FI to FR. Longer FI still flattened the scallop. The 1967 study simply swaps FR for VI and sees the same downward pull, confirming the interval rule holds across partner schedules.

When you build chained programs—like work first, then access to tickles—keep an eye on the second link. A long wait in the final step can cool off responding in the opening step. If early engagement drops, try shortening the later interval or adding brief checks so the learner feels the next reinforcer is close.