Self Control and Intertemporal Choice: Evidence from Glucose and Depletion Interventions∗

Recent economic theories model intertemporal choice as a problem of willpower or self control, i.e. of restraining a natural impulse to consume today. We use two interventions that have been shown by psychologists to affect self-control to examine whether this applies to the intertemporal savings decision, as measured in a laboratory elicitation of time preference. Contrary to the predictions of willpower-based models, we find that prior participation in an impulse-controlling activity (“depletion”) increases savings. Consistent with those models, sugared-drink consumption raises savings relative to a sugar-free placebo, but the placebo drink also raises savings (relative to no drink) by about the same amount. All these treatment effects are driven by increases in the intertemporal substitution elasticity and are much stronger among subjects with average (as opposed to high) cognitive ability. Overall, we suspect that factors like subjects ’ attention to the details of the decision are affected by our interventions and are more relevant to the financial decisions we model than are differences in willpower and body-energy budgets. JEL classification: C91, D9