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Willpower is a Limited Resource

In a landmark 1998 study, 67 people were tested to try to determine if willpower was a limited resource. The scientists were able to show that they could deplete willpower in their test subjects through a very simple mechanism, chocolates and radishes.

The experimenters setup a waiting room with a tray of snacks; half the tray filled with radishes and the other with chocolates. One group of participants was instructed to wait in the room and eat the chocolates, while the other group was made to wait in the same room but only allowed to eat the radishes (a third group was used as a controls and wasn’t presented with either food). After they waited and snacked in this room, each of the participants was tasked with completing an impossible geometry puzzle. The experimenters were measuring how long it took each participant to give up on trying to solve it, and the results confirmed their suspicions.

The chocolate group spent 19 minutes trying to solve the puzzle before quitting (The control group gave up after 20 minutes, statistically the same as the chocolate group). The second group, the one tasked with eating radishes and ignoring the chocolate, worked for only 8 minutes before giving up. The radish group gave up more than twice as fast as the chocolate group. The theory of why this happened comes down to what the experimenters term ‘ego depletion’, that the subjects eating the radishes used up their willpower reserves and thus had less willpower to use in the puzzle test. In the years since, this result has been confirmed again and again in related studies.

Let me step back a moment and define the terms. I used willpower in the title of this article as that is the most recognizable term to describe the effect, however the technical term is ‘ego depletion’. Roy Baumeister, perhaps the leading researcher on the subject and one of the authors of the radishes experiment, defines it this way: “The core idea behind ego depletion is that the self’s acts of volition draw on some limited resource, akin to strength or energy and that, therefore, one act of volition will have a detrimental impact on subsequent volition.” In short, willpower is finite.

The studies show that this same quantity is linked to everything you would normally think of as self-control. Namely:

  • Focus and Concentration
  • Decision making
  • Suppressing emotions
  • Pushing yourself during a workout
  • Etc.

It’s a measurable physical effect as well. In one experiment, subjects that underwent willpower depletion were shown to have lower glucose levels than subjects who did not. And similarly, feeding ego depleted subjects a sugar-sweetened drink seemed to restore some of their willpower (compared to giving them a drink with artificial sweetener). Glucose, a simple sugar used by your body for fuel, is the primary fuel source used by the brain.

Why You Should Care

Sure it’s an interesting experimental result, but what’s really great about the theories of ego depletion are their applicability for personal productivity.

In his book, Daily Rituals, Mason Currey describes the daily rituals of highly creative people. Overwhelmingly, he reports that most of them maintained a set of routines and rituals each day, keeping every day relatively similar. As a recent example, Steve Jobs famously wore the same clothes every day, since while he couldn’t control his daily schedule he could control what he wore each day.

The key point here is not necessarily what any of the rituals actually are, but the fact that they exist at all. What matters is not that Steve Jobs wore the same thing every day, or that Charles Darwin went for a walk every day at noon, but that they did not have to waste their willpower on deciding what to do or wear. Instead, creatives with a ritual are free to use all of their available willpower on the pursuits that they care about.

The studies also show that willpower can be restored via food, sleep, and time. So for many people the morning may be the best time to do your most focus intensive work; that’s when your willpower stores are at their highest.

Apply the Science

There are a lot of useful nuggets we can draw from this concept. Most important is to simply stay aware of this fact while planning your schedule. Try scheduling your intense work early in the day. Avoid decision making wherever possible on the least useful parts of your day.

Perhaps most importantly, instead of looking at tomorrow’s empty schedule by saying ‘I’ll figure out what to do in the morning’, rephrase that to be ‘I’m going to use up my limited focus tomorrow morning by checking email and deciding what to work on.’ If you’re still comfortable with that, by all means go ahead.

Further Reading: Roy Baumeister co-wrote an excellent book that explores this in depth. Willpower: The Greatest Human Strength