Amount of reward has opposite effects on the discounting of delayed and probabilistic outcomes

Previous research has shown that the value of large future rewards is disco unted less steeply than is the value of small future rewards. These experim ents extended this line of research to probabilistic rewards. Two experimen ts replicated the standard findings for delayed rewards but demonstrated th at amount has an opposite effect on the discounting of probabilistic reward s. That is, large probabilistic amounts were discounted at the same or high er rates than small amounts. Although amount had opposite effects on the di scounting of delayed and probabilistic rewards, nevertheless, the same form of mathematical function accurately described discounting of both types of reward. The findings suggest that fundamentally similar, but not identical , processes are involved in decision making regarding delayed and probabili stic rewards. The implications of these findings for impulsivity and self-c ontrol are discussed.