Risk sensitivity in intertemporal choice: A synthesis of foraging and behavioral economic theory.

摘要

Decision scenarios used in delay discounting research typically have little in common with real economic environments, wherein intertemporal choice at the molecular level is nearly always tied to some larger extended set of contingencies. Nevertheless researchers often treat discounting as a stable attribute of the individual, and assume that discounting generalizes across decision scenarios. Synthesizing theory from behavioral ecology and behavioral economics, the current study tested a preliminary model of delay discounting in extended financial contexts. Specifically, based upon the empirical relationship between risk sensitivity and energy budget constraints found in studies of foraging behavior, it assessed the possibility that molar environmental contingencies might produce reliable changes in sensitivity to delay. Eighty-two participants played an electronic video game involving a spaceship that searches for items on various planets. During the game, participants made a series of intertemporal tradeoffs regarding fuel for the spaceship, which were necessary in order for them to continue with the task. Smaller amounts of fuel were available immediately, while larger amounts were available after varying delay periods. Successful completion of the game was tied to a cash reward. Manipulations of molar environmental constraints involved changes in remaining game time and rate of fuel depletion. As hypothesized, participants' intertemporal tradeoffs showed progressively steeper discounting of fuel over the course of the extended task, reflecting distinct changes in sensitivity to delay. Individual difference variables customarily used to predict impulsivity showed little or no relationship to discounting in this context. These findings have several implications. First, they undermine the presumption that delay discounting is an index of a stable impulsivity trait. Second, they suggest that individual discount rates are partially a function of broader contextual variables. The data underscore the need to emphasize behavioral context and molar contingencies in the ongoing study of intertemporal decision-making.