Contingency and stimulus change in chained schedules of reinforcement.

Researchers worked with pigeons in a small lab. They set up three kinds of reward lines.

In the chained line, a light color told the bird the next step was coming. In the tandem line, the same steps ran but no light changed. In the mixed line, steps and lights shuffled.

The team counted pecks in each line to see if the light change itself worked like a tiny reward.

Birds pecked fastest in the chained line. The simple color switch boosted work even though food stayed the same steps away.

The light change acted like a conditioned reinforcer. It told the bird "you're closer,

Bejarano et al. (2007) later tested the same chained line but made the light change depend on how fast the bird pecked. Stimulus change still pushed responding, yet the old delay-to-food rule did not predict the strength. Their work stretches the 1980 finding: the cue itself matters, not just how close food is.

Davison et al. (2010) showed that a stimulus must be both response-contingent and well-correlated with the next food spot to stay powerful. This sharpens the 1980 result: pairing alone is not enough; the learner must see the cue depend on what it does.

Baer (1974) ran chained lines earlier and framed reinforcement as a simple situation shift. The 1980 study keeps that idea but proves the shift itself can be the reward.

Your clients also work through chains: wash hands, flush, get praise. Add a brief, clear cue at each step—like a click or a light—so the signal itself becomes a tiny reward. Make the cue happen right after the response and tie it to the next reinforcer. You should see smoother, faster chains without extra candy or screen time.