Effects of deprivation level on humans' self-control for food reinforcers.

Deprivation level was manipulated in fourteen food- and water-deprived adult human females to examine its effects on self-control for food (choice of larger, more delayed access to apple juice over smaller, less delayed access to apple juice). Each subject was exposed to two treatments: (1) Consumption of a 500 g tomato soup preload just prior to self-control testing and (2) no soup preload. When subjects had consumed soup, they reported significantly less hunger and showed significantly more self-control as compared to when not having consumed soup. Additionally, when subjects had consumed soup, self-control decreased as a function of session time. Subjects who reported that they were currently dieting drank significantly less juice when they had previously consumed soup than when they do not previously consumed soup. Together, the results indicate that when subjects are more deprived they may be less able to wait for food reinforcers (i.e., show less self-control). Such behaviour may be adaptive in situations in which energy is needed to survive periods of food scarcity.