External responsiveness to food and non-food cues was studied among 306 obese and nonobese boys and girls ranging in age from 42 to 156 months. These subjects viewed 5 food and 5 non-food items and stated a preference between an immediate smaller and a delayed larger choice. When presented with food items, obese subjects were less able than the nonobese to delay an immediate smaller gratification to maximize reward magnitude. No significant differences were found between obese and nonobese children regarding nonfood delay choices. These findings are discussed in terms of ontogeny of externality, the cause of some forms of obesity. A significant age difference indicated that preschool children preferred more immediate gratification than did school children. This age difference is consistent with research on delay of gratification using a choice paradigm. / M.S.