Spaced food but not electrical brain stimulation induces polydipsia and air licking.

Scientists gave rats food pellets every 60 seconds. The rats were not thirsty.

Some rats also got tiny electric pulses in the brain at the same time.

The team watched if the rats started drinking water between pellets.

Food pellets made the rats drink lots of water even though they were full.

Brain pulses never made the rats drink.

Only food caused the extra drinking, not any reward.

Corfield-Sumner et al. (1977) got the same result with a fancier food schedule. Their data back up the food-only rule.

Bacon-Prue et al. (1980) showed the pellet itself works like a cue. Their work extends this paper by proving the drinking follows the pellet signal.

Hart et al. (1974) looks like a clash: they saw less drinking when the schedule got harder. The gap is real—DRL timing cuts drinking, while steady FI timing lets it grow.

You now know that schedule-induced behaviors are picky. Food pellets open the door; other rewards do not. When you set up reinforcement plans, think about the reward type. If you see odd behaviors like over-drinking, check if food is on a fixed timer and consider switching the reward or timing to stop the side effect.