Magnitude Effects in Delay and Probability Discounting When Monetary and Medical Treatment Outcomes Are Discounted

Delay and probability discounting occur when the subjective value of an outcome decreases because it is delayed or uncertain, respectively. Research using monetary outcomes has shown that both types of discounting are influenced by the magnitude of the outcome, but in the opposite direction. In Experiment 1, university participants completed a delay-discounting task involving hypothetical monetary ($100 or $100,000) or medical treatment (acne or brain cancer) outcomes. In Experiment 2, university participants completed a probability-discounting task involving those same outcomes. Results from Experiment 1 replicated previous research in that participants discounted the “smaller” outcomes ($100 & acne treatment) more than the “larger” ones ($100,000 & brain-cancer treatment). Results from Experiment 2 demonstrated that this magnitude effect reversed for probability discounting of the monetary outcomes, with $100,000 discounted more than $100. However, acne treatment was discounted more than brain-cancer treatment. This study represents the novel finding that the magnitude effect for medical outcomes may not reverse between delay and probability discounting as it does for monetary outcomes. The results suggest that delay and probability discounting are at least partially independent.