Willpower Is Not a Tank That Runs Empty

Many of us think of willpower as a tank that empties during the day: use it up on emails and meetings, and nothing is left for the gym or a salad at dinner. It is an intuitive idea and it has been popular in psychology for years. The research behind it has not held up as well as the idea has spread. This is general education, not medical advice or therapy.

Where the idea came from

In the late 1990s, psychologist Roy Baumeister and colleagues proposed “ego depletion”: self-control draws on a limited resource, so using it on one task leaves less for the next. In the classic experiments, people who first resisted tempting cookies, for example, gave up sooner on a frustrating puzzle. The idea spread widely, in books, workplaces and diet advice.

The replication

In 2016, Martin Hagger and colleagues organized a large, preregistered replication in Perspectives on Psychological Science. Twenty-three laboratories, with 2,141 participants in total, ran the same standardized ego-depletion procedure. The overall effect was essentially zero (an effect size around 0.04, with a range that included no effect at all).

The debate that followed

• Critics of the replication. Supporters of the original theory argued that the tasks used were not a fair test, and the authors responded in print.
• Other research. Later meta-analyses also questioned how big, or how real, the original effect was.
• The upshot. The simple picture, in which self-control is a tank that drains in a predictable way, is far less settled than it was presented.

That does not mean self-control never feels harder when you are tired, stressed or hungry. It means that “running out of a fixed supply” is probably not the best way to describe it.

What seems more useful

• Change the environment. It takes less effort not to eat what is not in the house. Fewer decisions means fewer chances to slip.
• Plan ahead. If-then plans turn a decision into a cue and a response. See our guide to if-then plans.
• Build habits. Habits take over where deliberate effort would be needed. See how long a new habit takes.
• Look after the basics. Sleep, food and stress all shape how easy choices feel. Our guide to stress eating covers one example.
• Be kind about slips. Harsh self-judgment tends to make the next lapse more likely, as we describe in being kind to yourself after a slip.

A more forgiving view

If you have been blaming yourself for running out of willpower at 8 p.m., the research suggests you may be blaming the wrong thing. Often the better question is not “how do I try harder?” but “how do I make the right choice easier?” A small change to your surroundings can do more than a pep talk.

Sources

• Hagger MS, Chatzisarantis NLD, Alberts H, et al. A multilab preregistered replication of the ego-depletion effect. Perspectives on Psychological Science, 2016;11(4):546-573.
• Baumeister RF, Bratslavsky E, Muraven M, Tice DM. Ego depletion: is the active self a limited resource? Journal of Personality and Social Psychology, 1998;74(5):1252-1265.