Punished and unpunished responding in multiple variable-interval schedules.

The team placed pigeons on two VI schedules at once. One schedule paid off often. The other paid off rarely.

After the birds pecked steadily, every peck in both schedules met a quick shock. The shocks stayed on for many sessions. Then they stopped.

The researchers watched if the birds learned to peck more in the rich side and less in the lean side.

Shocks cut pecking by the same percent in both schedules. Rich or lean, the drop looked identical.

When the shocks ended, the birds still pecked in the same ratio. They did not return to old levels, but the small error rate held steady.

Kruper (1968) ran the same year with the same result. Birds on concurrent VI schedules also dropped the same percent, showing the effect is real.

Schroeder et al. (1969) moved the test to adult humans. People on VI schedules also slowed down when shocks arrived, proving the law crosses species.

McKearney (1970) added VR schedules and saw a twist. VR responding fell faster than VI as shock grew, and VI bounced back sooner when shock eased. So equal suppression only holds when both sides are interval schedules.

For BCBAs, the key point is that punishment strength, not reinforcement size, drives the drop. If you add a punisher to two behaviors, expect the same cut even if one earns more tokens. Watch for slow recovery once the punisher stops, and plan extra teaching trials to bring rates back.