The effect of risk on intertemporal choice

The strong similarities between intertemporal and risky choice raised the possibility that risk and time delay were psychologically interchangeable in the way they influence preference. Consistent with the single-process view, several previous studies have indicated that introducing uncertainty to intertemporal choice could decrease the degree of discounting future rewards just as adding time delay to it. However, the opposite effect has been observed in other cases. The present study examined the role of risk in intertemporal choice using the choice titration procedure. The results of two experiments indicated that risk and time delay had opposite effects on the preference in intertemporal choices. That is, the external uncertainty increased the degree of discounting future, whereas the opposite is true for time delays. Thus, our results were unfriendly to the single-process theory. In addition, the present study demonstrated the presence of an immediacy effect as well as a magnitude effect in intertemporal choice regardless of whether or not the reward is certain.