The present values of delayed rewards are approximately additive

In two experiments, human subjects were asked to estimate their present values of single delayed rewards and their present values of temporal sequences of three rewards. Present values were solicited by asking subjects to indicate an amount of money vv for which they would be indifferent between receiving vv at the end of the session and receiving the delayed reward(s). A procedure was used for which responding the true value of vv was the optimal strategy, and the actual payoff that each subject received was determined by one randomly selected trial. In Experiment 1 (n = 29) each delayed reward was $9.90 in cash. In Experiment 2 (n = 19) the delayed rewards were dated $15 gift certificates to a local restaurant. In both experiments, the present values of the sequences were approximately equal to the sums of the present values of their component rewards. The presence of outliers suggests that a few subjects may have valued sequences less than the sums of their single rewards. Effects of a preference for uniform sequences, if any, were too small to be detected. Discounting of sequences was well fit by a parallel hyperbolic discounting equation, consistent with Mazur's [Mazur, J.E., 1986. Choice between single and multiple delayed reinforcers. J. Exp. Anal. Behav. 46 (1), 67–77] results using multiple reinforcers.