Is time-discounting hyperbolic or subadditive?

Subadditive time discounting means that discounting over a delay is greater when the delay is divided into subintervals than when it is left undivided . This may produce the most important result usually attributed to hyperbol ic discounting: declining impatience, or the inverse relationship between t he discount rate and the magnitude of the delay. Three choice experiments w ere conducted to test for subadditive discounting, and to determine whether it is sufficient to explain declining impatience. All three experiments sh owed strong evidence of subadditive discounting, but there was no evidence of declining impatience. I conclude by questioning whether hyperbolic disco unting is a plausible account of time preference.