Ten dollars today is more attractive than the same amount of money tomorrow and is consistent with the well known proverb, “a bird in the hand is worth two in the bush”. We all know that the value of a reward is discounted over time. How the value discounts over time and what is the rationale for such discounting, however, is less clear. Here is my version of explanation.
http://www.frontiersin.org/integrative_neuroscience/10.3389/fnint.2011.00024/full