RATE OF TEMPORAL DISCOUNTING DECREASES WITH AMOUNT OF REWARD

The present, subjective value of a delayed reward is a decreasing func tion of the duration of the delay. This phenomenon is termed temporal discounting. To determine whether the amount of the reward influences the rate of temporal discounting, we had subjects choose between immed iate and delayed hypothetical rewards of different amounts ($100, $2,0 00, $25,000, and $100,000 delayed rewards). As predicted by psychologi cal models of the choice process, hyperbolic functions described the d ecrease in the subjective value of the delayed reward as the time unti l its receipt was increased (R(2)s from .86 to .99). Moreover, hyperbo lic functions consistently provided more accurate descriptions of the data than did exponential functions predicted by an economic model of discounted utility. Rate of discounting decreased in a negatively acce lerated fashion as the amount of the delayed reward increased, levelin g off by approximately $25,000. These findings are interpreted in the context of different psychological models of choice, and implications for procedures to enhance self-control are discussed.