Schedule-induced stereotypy.

Mazur et al. (1992) watched eight adults with severe intellectual disability during simple reinforcement sessions.

The team used fixed-interval schedules: a reinforcer came only after a set time had passed.

They tracked whether each person’s body-rocking, hand-flapping, or other stereotypy got worse right before the next reward.

Seven of the eight adults showed more stereotypy as the interval ticked on.

Five of them locked their repetitive moves to the early part of the wait-time, a pattern called entrainment.

In plain words, the schedule itself seemed to stir up the behavior you usually try to stop.

SHETTLEWORTCHARNEY et al. (1965) first showed that intermittent schedules create predictable pauses and bursts with any reinforcer.

Schwarz et al. (1970) added that, under fixed-interval, the sixth response after a reward marks when timing steadies—helping explain why stereotypy settles into the same early slot.

Alsop et al. (1995) later found that intermittent schedules weaken rule-following in typical adults, while E et al. saw the same schedules amplify unwanted movement in clients with ID.

Together the chain shows: the schedule drives the pattern; the population decides whether you lose compliance or gain stereotypy.

If you run fixed-interval or any lean schedule, watch for a bump in stereotypy right after the reinforcer. Try shortening the interval, adding a brief DRL, or inserting a non-verbal cue to break the timing trap. A quick schedule tweak can save you weeks of stereotypy reduction programs.