Longitudinal Tests of Intertemporal Preference Reversals Due to Hyperbolic Discounting

Abstract

Hyperbolic discounting of delayed rewards has been proposed as the underlying cause of the failure to stick to plans to forego one’s immediate desires, such as the plan to diet, wake up early, or quit taking heroin. These planning failures could, however, result from other mechanisms that prior studies have not ruled out. We conducted two tests of inconsistent planning in which respondents made at least two choices between a smaller-sooner (SS) and larger-later (LL) amount of money, one several weeks before SS would be received, and one immediately before. Hyperbolic discounting predicts that there would be more choices of SS as it became more proximate – and, equivalently, that among those who change their mind, “impatient shifts” (LL-to-SS) will be more common than “patient shifts” (SS-to-LL). In fact, however, we find no evidence for this. We argue that the evidence for a non-stationary internal discount function is weaker than traditionally assumed and that qualitatively different psychological mechanisms may cause the behaviors often attributed to hyperbolic discounting.