Figure 3.

Hyperbolic discounting of delay. This function describes theoretical data from an experiment in which two groups of animals are given a choice between two arms of a maze, one of which contains a larger-later reward, four food pellets that necessitate a wait of 15 s, and one which contained a smaller-sooner reward, two food pellets that were available after 3 s. (A) Value as a function of delay for a single reward magnitude, two food pellets, computed according to Eq. 2.3. The discount function is depicted for two values of k with higher k indicating steeper, (more impulsive) discounting. (B) Value as a function of reward magnitude for the two different and delays, 3 and 15 s, computed using the same equation. The circles show the two options presented to the two groups of animals. In this example the value of the larger-later reward is greater for the less impulsive group, and the value of the smaller-sooner reward is greater for the more impulsive group. (C) Value as a function of both delay and reward magnitude.