Time discounting: Declining impatience and interval effect

Most studies have not distinguished delay from intervals, so that whether the declining impatience really holds has been an open question. We conducted an experiment that explicitly distinguishes them, and confirmed the declining impatience. This implies that people make dynamically inconsistent plans. We also found the interval effect that the per-period time discount rate decreases with prolonged intervals. We show that the interval and the magnitude effects are caused, at least partially, because subjects' choices are influenced by the differential in reward amount, while Weber's law solves neither the delay nor the interval effects.