The conditioning-delay gradient, not impulsivity, accounts for apparent steep delay discounting in monkeys (Macaca mulatta).

Nonhuman animals, like humans, often prefer smaller immediate reward over larger delayed reward, suggesting "discounting" of future reward. In studies of nonhuman animals, this preference is measured by offering repeated choices between icons resulting in smaller immediate or larger delayed reward. One possible mechanism driving discounting behavior is that subjects forget during the delay to reinforcement which option they chose at the beginning of the trial. If this account is correct, preventing forgetting should decrease apparent discounting. In Experiment 1, we tested this hypothesis by having monkeys choose between immediate and delayed reward with either a blank delay to reinforcement or with the chosen icon visible during the delay such that the icon could potentially remind monkeys of their choice. When the chosen icon remained visible, apparent discounting was significantly reduced. This result suggested that reminding was effective. However, keeping the chosen icon visible during the delay also meant that the icon was visible immediately prior to reward, potentially causing the icon to accrue more associative strength with reward than would occur when there was a temporal gap between the icon and reward. Experiment 2 distinguished between reminding and associative learning by hiding the icon after selection and briefly showing it before reward delivery. Apparent discounting remained attenuated. These results indicate that the conditioning-delay gradient is a strong determinant of the choices of monkeys in delay discounting paradigms and indicate that animal models may not capture the processes proposed to explain delay discounting in humans, such as impulsivity. (PsycInfo Database Record (c) 2026 APA, all rights reserved).