Interactions in multiple schedules: negative induction with squirrel monkeys.

Spealman (1978) worked with squirrel monkeys in a lab. The monkeys pressed levers under two alternating schedules. One schedule stayed the same. The other was switched to extinction or timeout.

The team watched what happened in the unchanged schedule. They wanted to see if stopping rewards in one part would hurt responding in the other part.

When rewards stopped in the changed part, response rates in the steady part dipped. This negative induction showed up fast. The dip faded after a few sessions.

The effect only appeared in monkeys. Earlier pigeon studies had seen the opposite. The paper warns that contrast effects may not cross species lines.

Davol et al. (1977) found you can shrink negative contrast by tweaking the schedule to skip long pauses. Spealman (1978) agrees the effect is fragile, but shows it can flip to negative if you use monkeys instead of pigeons.

Innis (1978), published the same year, saw mixed local contrast in pigeons under fixed-interval schedules. Both studies stress transient effects, yet species and schedule type change the direction.

Craig et al. (2018) later showed that off-baseline extinction in one part can weaken resistance in the other. This extends D’s core point: what happens in one component spills into the next, even without direct training.

If you run multiple schedules with clients, do not assume contrast will look the same across learners. Check for brief dips or surges right after you change reinforcement in one task. If you see a drop, wait a few sessions before adjusting; the effect may vanish on its own. And if you switch species or response forms, rerun your baseline—what helps pigeons might hurt monkeys.