Effects of a pre-shock stimulus on temporal control of behavior.

The team trained rats to press levers in a strict A-then-B order. The animals had to wait a set time between the two presses to earn food.

Next the rats heard a brief tone. Right after the tone they got a mild foot-shock they could not escape. The scientists watched how the warning tone changed the animals’ timing and accuracy.

The tone-before-shock broke the chain. Rats made fewer correct A-then-B sequences and started pressing B at the wrong times.

Their internal clock slipped. Most responses bunched up at shorter intervals, almost as if the rats were rushing to beat the shock.

Snapper et al. (1969) saw the same timing loss when shock came without any warning. Adding the tone in the 1970 study let the team pin the damage on the signal itself, not just the pain.

Garcia et al. (1973) later repeated the setup and got the same breakdown, showing the effect is reliable across slightly different lever tasks.

Kruper (1968) looked like a contradiction: monkeys warned by a tone kept their accuracy even though they slowed down. The difference is the task. Monkeys picked an ‘odd’ picture, a simple yes-or-no choice. Rats in the 1970 study had to judge time, a far shakier skill. Same warning, different job, opposite accuracy results.

If you use signals before unavoidable events—like a two-minute warning before a fire drill—know that the signal itself can scramble chained skills. Break tasks into small, clear steps and give extra practice after any aversive cue. For learners who must wait or count, consider shortening the interval or adding prompts until timing stabilizes again.