Operant conditioning of human anal sphincter pressure.

A young learners boy with encopresis learned to squeeze a balloon in his rectum. Each squeeze raised pressure on the balloon. The boy earned candy for every pressure jump. Researchers tried three pay schedules: every response, every other response, and every fourth response. They also tested what happened when candy stopped.

Candy made pressure go up. The boy hit higher peaks on the every-response schedule. When candy paused, pressure stayed high for a while, then slowly dropped. Each new candy phase pushed pressure higher than the last. The schedule itself shaped how hard and how often the boy squeezed.

Batchelder et al. (2025) paid adults cash for steps and saw the same pattern: intermittent pay still boosted the target response. Both studies show schedules work even when the response is unusual—steps or sphincter squeezes.

Russell et al. (2018) found tokens kept kids working after the kids had eaten their fill of candy. The 1973 study did the reverse: it used real candy to shape a brand-new response. Together they show you can start with candy and later swap in tokens or other reinforcers.

Michael (1974) showed pigeons would peck a key just to see a light that signaled food. The boy did not need a signal; the pressure change itself was the feedback. The two papers bracket how much or how little feedback you need to keep behavior going.

You can treat encopresis without drugs or diapers. A simple balloon, candy, and a schedule can teach a child the squeeze pattern needed for bowel control. If you run toilet-training or feeding programs, try pairing tiny edible rewards with clear body feedback. Start with continuous pay, then thin the schedule as pressure rises. The same tactic could work for other hidden muscles—think swallowing or vocal-fold control.