Effects of procurement cost on food consumption in rats

Rats deprived of food for 23 hr were given unconstrained access to food for 1 hr following the completion of a lever-press requirement. Four experimental subjects were each tested for 7 sessions in each of a series of lever-press requirement conditions (1, 5, 10, 20, 50, 100, 150, 200) with a free access condition before and after this series, and with a final return to the 100 lever-press condition. To each experimental subject was yoked an equally deprived control subject which received access to food independently of its own responding, at the same time as its experimental partner. The food consumption of the experimental subjects, but not that of the controls, increased systematically as the lever-press requirement increased. It is argued that the results suggest that the way the procurement cost of food is related to both the frequency and size of meals is due to a direct but independent effect of the cost on both meal size and latency to initiate eating.