Why Can “Today” Reverse a Choice between Sooner and Later Rewards?

Imagine someone who prefers $30 in thirty-one days to $20 in thirty days. As the dates approach, however, they choose $20 today rather than waiting until tomorrow for $30. Both choices involve a one-day gap, yet the preference has reversed.

Psychologists use delay discounting to describe how a reward usually loses subjective value as it moves further into the future. For many people, that decline is not a smooth, fixed proportion for every extra day. When the smaller reward becomes available “right now”, immediacy can give it extra weight. While both options are still in the future, the difference in amount stands out; once one arrives in the present, the psychological cost of another day's wait can dominate. This is often called present bias and can be approximated by hyperbolic or quasi-hyperbolic models. Such models describe choice patterns; they do not show that the brain literally calculates a particular formula.

A study of monetary choices among smokers and non-smokers found that an individual's degree of delay discounting predicted some preference reversals. This is not a fixed rule that everyone follows. Reward size, length of delay, trust that a promise will be honoured and pressure on current resources can all affect a choice. Laboratory tasks using hypothetical or small monetary rewards also cannot fully represent decisions about food, saving or health.

Changing one's mind as the present approaches should therefore not be reduced to “weak will”. A more precise conclusion is that temporal position has changed the subjective weight of the two rewards. To help an earlier plan survive, a person can reduce access to the immediate option before temptation arrives. That approach uses the fact that preferences change over time, but it cannot guarantee success.

https://doi.org/10.1037/pha0000224
https://doi.org/10.3389/fnbeh.2014.00076