Time and risk perceptions mediate the causal impact of objective delay on delay discounting: An experimental examination of the implicit-risk hypothesis

Abstract

Delay discounting refers to the decline in the value of a payoff as the objective delay to its fulfillment increases. Recent research on delay discounting has examined its relationship with time and risk perceptions through correlational studies. Manipulated experiments were conducted in the current research to further investigate the causal links among the relevant variables. Experiment 1 revealed causal influences of objective delay on both risk perception and delay discounting as well as a positive correlation between risk perception and delay discounting. By manipulating risk perception, Experiment 2 demonstrated further a causal impact of risk perception on delay discounting. Experiment 3 manipulated time perception and provided further evidence for causal pathways from time perception to risk perception and delay discounting. Overall, the results verified a causal chain from objective delay to delay discounting through time and risk perceptions in support of the implicit-risk hypothesis regarding delay discounting.

Appendix

The titration procedure for adjusting the amount of the immediate reward in the delay-discounting task

For each delay, the amount of the delayed reward was fixed at 40 CNY (Chinese Yuan) and two adjustment bounds were set for the immediate amount, with the initial upper bound (UB) equal to the delayed amount (i.e., 40 CNY) and the initial lower bound (LB) fixed at 0 CNY. The immediate amount was always equal to the average of the two adjustment bounds, leading to an initial immediate reward of 20 CNY. After each choice, the UB would be updated to the average of the UB after the previous trial and the immediate amount for the current trial if the immediate reward was chosen, or the LB would be updated to the average of the LB after the previous trial and the immediate amount of the current trial if the delayed reward was chosen. In either case, the immediate amount would be updated to the average of the two adjustment bounds as in the first trial. For each delay, the titration procedure would stop, and the updated immediate amount would be treated as the indifference point if the two bounds were sufficiently close to each other (i.e., the distance between the bounds was no more than 2 CNY). Unlike the common adjustment method in which the LB or UB was updated to the current immediate amount after the respective choice response, the titration procedure used in the current studies was more lenient and thus allowed for probabilistic choice responses which had enjoyed substantial support from empirical studies (e.g., Dai & Busemeyer, 2014). Consequently, the indifference points revealed by this titration procedure were more likely to approach the “true” indifference points whose choice probabilities against the delayed reward were 50%.