Pavlovian Conditioning of Hunger.
In a clever series of Pavlovian conditioning experiments on laboratory rats, Weingarten (1983. 1984, 1985) provided strong support for the view that hunger is often caused by the expectation of food, not by an energy deficit. During the conditioning phase of one of his experiments. Weingarten presented rats with six meals per day at irregular intervals, and he signaled the im pending delivery of each meal with a buzzer-and-light conditional stimulus. This conditioning procedure was continued for 11 days. Throughout the ensuing test phase of the experiment, the food was continuously available. Despite the fact that the subjects were never deprived during the test phase, the rats started to eat each time the buzzer and light were presented—even if they had recently completed a meal.