Negatively reinforced key pecking.

The team worked with four pigeons in a small chamber. A key glowed red. If the bird pecked it, a mild electric shock was skipped.

First, grain rewarded every peck. Then grain stopped. Only shock removal kept the birds pecking. The scientists raised and lowered shock strength to see how hard the birds would work.

All birds kept pecking even after food vanished. Stronger shock produced faster pecking. Weaker shock slowed the response, but it still stayed steady.

The birds were working to escape pain, not to earn snacks. Negative reinforcement alone held the behavior in place.

Brown et al. (1968) showed pigeons will peck a key that merely signals food. Shimp et al. (1974) shows the same response can be held by shock removal. Same movement, opposite reinforcer.

Hartmann et al. (1979) added a tone and kept grain. Their birds also kept pecking when responses canceled food, pointing to Pavlovian control. The 1974 study swaps grain for shock escape and still sees steady pecking, proving the topography is flexible across very different contingencies.

Azrin et al. (1967) built the shock chambers that made these studies possible.

If a client works to avoid something, the escape response can stick even when the original reward is gone. Check what is really holding the behavior in place—attention, tokens, or removal of annoyance. You might thin or fade the aversive stimulus instead of adding more goodies.