Habituation and within-session changes in motivated responding for food in children.

Within-session decreases in instrumental responding to obtain food, consistent with habituation, have been reliably demonstrated in adults and children. This study tested the hypothesis that within-session decreases in instrumental responding for food are due to habituation rather than satiation. Thirty-eight 8-12-year-old children performed a computer-based operant task to earn points toward access to potato chips for 20 min, and for chocolate candies for the final 6 min of the session. Portion size of the food reinforcer (75 kcal vs 225 kcal) and food consumption (consumption/no consumption). There was no difference in the rate of response decrease between the two portion size conditions. Both the consumption and non-consumption groups showed response decelerations during the first 20 min, with responses in the consumption group decreasing at a faster rate. When the novel food was presented, participants in all conditions recovered responding. Although satiation may contribute to reductions in motivated responding for food when food is consumed, habituation provides a more complete explanation for the results observed in this study.