People Wait Longer when the Alternative is Risky: The Relation Between Preferences in Risky and Inter-temporal Choice

In two experiments, we demonstrate that despite indicating indifference when probed about risk or delay in isolation, when forced to explicitly trade-off between the two, participants prefer delayed over risky rewards. This pattern of findings sets a boundary condition for any common utility-based comparison process involving both risk and delay. Furthermore, this change from indifference-in-isolation to delay-preference-in-a-trade-off strengthens as reward amount increases. Exploratory modeling results suggest that the shift in preference can be explained by allowing for different discount rates for delay-only choices compared with when delay is in competition with risk. This explanation is better than one in which probability weighting is different between risk-only choices and risks considered in the presence of a delay. Together, the empirical and modeling work lays a path for future investigations of why and when people's evaluation of the properties of risky and delayed choices vary as a function of the alternatives on offer.