Stevens, et al. (2005) tested temporal preferences in two closely related species of monkeys, cotton-top tamarins and common marmosets. Though similar in many ways, these two species differ in one crucial aspect: their diets. Tamarins eat primarily insects—which require quick action to capture—whereas marmosets feed primarily on sap and gum exuding from trees (Snowdon & Soini, 1988; Stevenson & Rylands, 1988). Marmosets chew on tree bark and wait for seconds, minutes, or hours for the sap to flow. Thus, the marmosets are adapted to waiting for food. In a self-control paradigm, marmosets waited almost twice as long as tamarins for the same amount of food (Stevens et al., 2005).
I think it would be interesting to do a comparative brain study of these monkeys and see which factors result in this difference in discounting, and test predictions by attempting to change them
In fact, it'd be even more fruitful to apply the same knowledge to other primate species and rein in their irrationality, too