Conditioned suppression of an avoidance response.

The team worked with rats that had learned to press a lever to avoid shocks.

They added a 30-second tone that came right before some shocks.

They watched if the tone made the rats press more, press less, or get shocked more often.

Sometimes the tone made the rats freeze and stop pressing.

Other times the same tone made the rats press faster.

In every case the rats got more shocks when the tone was on, even when they pressed more.

Hearst et al. (1970) saw the same freeze-and-more-shocks pattern one year earlier.

Liberman et al. (1973) later showed rats will pick the tone even when it brings eight times more shocks, because the tone also marks safe periods.

Hymowitz (1981) found the same mixed results when shock strength and body weight changed, showing the effect is not simple.

These studies together tell us the tone works as both a danger cue and a safety cue, and the balance shifts with timing and choice.

When you add a warning stimulus to any avoidance program, watch what the client actually experiences, not just what they do. A signal that cuts behavior may still raise the rate of the very event you want to avoid. Check the whole contingency before you call it a success.