1. Delay Discounting of Qualitatively Different Food Rewards in Rats Amanda L. Calvert Washington University in St. Louis
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3. The slope of the discounting function is expressed by the free parameter k : V = A / (1 + k D ). As k increases, the slope of the discounting function becomes steeper. In other words, as k increases, the reward looses value more quickly with increasing delay. It appears that the rate at which delayed rewards are discounted is not invariant, even within individuals .