Effects of food deprivation on free-operant avoidance behavior.

Scientists put rats in a cage with a lever. Every 5 seconds a mild shock came unless the rat pressed the lever.

First the rats ate all they wanted. Then the team cut food until each rat weighed only a large share and later a large share of its free-feed weight. After that they let the rats eat freely again.

They counted how many times the rats pressed and how many shocks they got at each weight.

Hungry rats pressed the lever less. Shock rate jumped from near zero to about one shock every minute.

When free feeding returned the rats pressed more and shocks dropped again. Less body weight meant less avoidance.

Horton (1975) saw the opposite: rats pressed like crazy when each press only delayed shock. That study changed the rule, not the rat’s hunger. Together the papers show lever pressing depends both on the contingency and on the rat’s body state.

Eisenmajer et al. (1998) found that unsignaled delays made food reinforcement weaker. Kelly (1973) shows that less food also weakens behavior, even when the task is avoiding shock instead of getting food. Both warn that anything that muddles or reduces food value can drop responding.

Coburn et al. (1976) reared rats in dull or rich cages and saw different willingness to work for food. Adding Kelly (1973), we learn that past environment and current body weight both shape how hard a rat will work.

If you run avoidance or safety drills with animals, keep their weight stable. A sudden diet can make your subject look like the intervention failed when it is really just too hungry to respond. Check feeding records before you change your procedure.