There is ample evidence that humans are impatient. The traditional assumption in Economics has been to assume that we have preferences that exogenously feature a discount factor. Isabelle Brocas and Juan Castillo claim to explain endogenously impatience by thinking about how the brain functions.
Essentially, the brain is composed of competing entities. Say that there is a principal maximizing undiscounted intertemporal utility on a finite horizon. Then, there are distinct agents in each periods, all myopic in the sense that only contemporaneous utility matters. The principal can impose choices on agents, but the latter have private information on marginal utilities. The problem is closed with an intertemporal budget constraint with a strictly positive interest rate.
Impatience emerges as a result of this asymmetric information. Each agent has independent valuation, so there is no information to be gained from one agent that would be useful on the others. However, the principal can elicit some valuation revelation by granting more immediate utility to the agent. Thus, impatience is the result of asymmetric information between the principal and the independent agents.
In the particular implementation of this problem, the only intertemporal binding is the interest rate. This is the reason why the principal wants some savings. In the model, this positive interest rate is exogenously imposed. If it is zero, there is no impatience. Then, why would the interest rate be positive in the first place? Isn't it to reward patience among impatients? Aren't we going in circles here?