Choice of higher density signalled shock over lower density unsignalled shock.

Liberman et al. (1973) let rats pick between two shock schedules. One side gave shocks with a bright light first. The other side gave shocks with no warning. The signalled side could have up to eight times more shocks.

The rats lived in a two-lever box. Pressing a lever switched the schedule for the next 5 min. Sessions ran until each rat showed a clear favorite.

Every rat stayed on the signalled side almost all the time. They picked eight shocks with a warning over one shock without it.

Even when the signalled side gave eight times more shocks, the rats still chose it. The safety signal mattered more than shock count.

Glover et al. (1976) later stretched the gap between shocks. When the gap was 150 s, rats still loved the signal. When the gap shrank to 45 s, the signal lost value and rats flipped. Timing changes how much safety a signal gives.

Lewis et al. (1976) made the safety light blink wrong half the time. Rats still picked the signalled side as long as the light ever meant safe. The danger cue can be messy, but the safety cue must be clear.

Shimp et al. (1974) flipped the test to food. Pigeons picked signalled grain over surprise grain, mirroring the rat shock result. Signals boost value for both good and bad events.

Your learners will work harder to know what is coming next. A two-minute warning before a hard task can calm more than cutting the work in half. Use clear start and end signals during hygiene, transitions, or medical checks. Keep the safe-period cue honest and short; a broken promise hurts more than no promise.