I once asked a room full of about 100 neuroscientists whether willpower depletion was a thing, and there was widespread disagreement with the idea. (A propos, this is a great way to quickly gauge consensus in a field.) Basically, for a while some researchers believed that willpower depletion "is" glucose depletion in the prefrontal cortex, but some more recent experiments have failed to replicate this, e.g. by finding that the mere taste of sugar is enough to "replenish" willpower faster than the time it takes blood to move from the mouth to the brain:

Carbohydrate mouth-rinses activate dopaminergic pathways in the striatum–a region of the brain associated with responses to reward (Kringelbach, 2004)–whereas artificially-sweetened non-carbohydrate mouth-rinses do not (Chambers et al., 2009). Thus, the sensing of carbohydrates in the mouth appears to signal the possibility of reward (i.e., the future availability of additional energy), which could motivate rather than fuel physical effort.

-- Molden, D. C. et al, The Motivational versus Metabolic Effects of Carbohydrates on Self-Control. Psychological Science.

Stanford's Carol Dweck and Greg Walden even found that hinting to people that using willpower is energizing might actually make them less depletable:

When we had people read statements that reminded them of the power of willpower like, “Sometimes, working on a strenuous mental task can make you feel energized for further challenging activities,” they kept on working and performing well with no sign of depletion. They made half as many mistakes on a difficult cognitive task as people who read statements about limited willpower. In another study, they scored 15 percent better on I.Q. problems.

-- Dweck and Walden, Willpower: It’s in Your Head? New York Times.

While these are all interesting empirical findings, there’s a very similar phenomenon that’s much less debated and which could explain many of these observations, but I think gets too little popular attention in these discussions:

Willpower is distractible.

Indeed, willpower and working memory are both strongly mediated by the dorsolateral prefontal cortex, so “distraction” could just be the two functions funging against one another. To use the terms of Stanovich popularized by Kahneman in Thinking: Fast and Slow, "System 2" can only override so many "System 1" defaults at any given moment.

So what’s going on when people say "willpower depletion"? I’m not sure, but even if willpower depletion is not a thing, the following distracting phenomena clearly are:

  • Thirst
  • Hunger
  • Sleepiness
  • Physical fatigue (like from running)
  • Physical discomfort (like from sitting)
  • That specific-other-thing you want to do
  • Anxiety about willpower depletion
  • Indignation at being asked for too much by bosses, partners, or experimenters...

... and "willpower depletion" might be nothing more than mental distraction by one of these processes. Perhaps it really is better to think of willpower as power (a rate) than energy (a resource).

If that’s true, then figuring out what processes might be distracting us might be much more useful than saying “I’m out of willpower” and giving up. Maybe try having a sip of water or a bit of food if your diet permits it. Maybe try reading lying down to see if you get nap-ish. Maybe set a timer to remind you to call that friend you keep thinking about.

The last two bullets,

  • Anxiety about willpower depletion
  • Indignation at being asked for too much by bosses, partners, or experimenters...

are also enough to explain why being told willpower depletion isn’t a thing might reduce the effects typically attributed to it: we might simply be less distracted by anxiety or indignation about doing “too much” willpower-intensive work in a short period of time.

Of course, any speculation about how human minds work in general is prone to the "typical mind fallacy". Maybe my willpower is depletable and yours isn’t. But then that wouldn’t explain why you can cause people to exhibit less willpower depletion by suggesting otherwise. But then again, most published research findings are false. But then again the research on the DLPFC and working memory seems relatively old and well established, and distraction is clearly a thing...

All in all, more of my chips are falling on the hypothesis that willpower “depletion” is often just willpower distraction, and that finding and addressing those distractions is probably a better a strategy than avoiding activities altogether in order to "conserve willpower".

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An even more recent study has failed to replicate the glucose effect entirely, too: Lange, F., & Eggert, F. (2014). Sweet delusion. Glucose drinks fail to counteract ego depletion. Appetite, 75, 54-63 <-- This one also has an interesting survey of the methodological flaws in similar studies.

Also, there's some evidence (still preliminary) that ego depletion effects decline with age: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0026351 <-- free access paper if anyone wants to read it. It basically looks at a meta-analysis by Hagger done about 2010? I think, and shows a significantly higher effect for younger people (which, being psyc and reliant on college students most of the time, is most of them) - then conducted their own study and found the same (using groups of <25 vs. 40-65). Since 25 is approximately when the pre-frontal cortex is fully finished maturing, maybe the effect has something to do with that.

Also, in terms of the 'out of willpower' and giving up thing... several studies have shown that with sufficient incentive (money, being told the research will help develop Alzheimer's therapies) the ego depletion effect goes away (but then comes back triple-fold on a third non-motivated task). Also, people tend to conserve willpower when they expect to need it later. So you don't have to give up, it might just be a bit harder - but if a few dollars (literally what it was) can motivate someone out of it then you can probably motivate yourself out of it for anything important. This is where the muscle analogy comes into play, like an athlete resting for a big match then pushing through discomfort during it.

^Ref for the last paragraph: Muraven, M., Slessareva, E. (2003). Mechanisms of Self-Control Failure: Motivation and Limited Resources. Personality and Social Psychology Bulletin, 29(7), 894-906

All in all, I'm not convinced one of those things is going on, because there's no explanation there as to why they would happen more for a task that requires self-control than one that doesn't. Most ego-depletion studies match up tasks to make them the same domain, often the same length and tediousness. Why would a task requiring more self-control give you more physical discomfort, hunger, thirst or indignation? The anxiety about willpower depletion I can get behind, but that's only for people who know what they're being tested on.

I find the "Sweet delusions" paper to be quite unconvincing on a close reading. They use a very different task than any previous trial (selected for having a much, much high test-retest reliability--strongly suggesting that performance is less contingent on state!), but still suppose that the effect size of glucose depletion should be the same as in the literature (I have no idea why you would think this).

They find a large and statistically signifiant effect post-treatment---the glucose group has much higher willpower. But they also find a large and statistically significant effect pre-treatment, and so recourse to a more sophisticated analysis. This is inconsistent with the treatment effect observed in the original studies, but to be frank this is unsurprising given the high test-retest reliability of the measure they chose.

In fact it looks like they find substantially higher willpower in the second trial (with a larger improvement in the control group, going along with their much lower levels of initial willpower). This contradicts many well-replicated results, and seems like a good pointer that they may not be measuring willpower. It's also quite easy to see a number of ways in which this could happen as an artifact of their methodology.

They later produced a second replication with the same subjects. They fail to find an effect, but they use "tendency to clear more lines at a time in tetris" as their measure of self-control, which as far as I know has never been used in another study and doesn't seem very compelling to me. I don't know why in god's name they wouldn't just replicate with any one of a dozen standard tests of willpower depletion. I would be curious if anyone has insight into this.

It looks like neither paper has any other citations, though they have seen a good bit of popular discussion. My best guess is that this is another example of it being easy for a crappy replication to fail to reproduce an effect regardless of whether it is real.

I remain agnostic about the original effect (at least relative to my disdain for this study). It looks to me like the evidence is reasonably good, and if true it certainly seems like an important fact. I'd be curious if anyone has thoughts on it.

ETA my best guess: willpower depletion is real, the perception of glucose (but not an artificial sweetener) really does help a lot with performance 10m later if in a depleted state, and recently agreeing to "I don't think willpower depletion is real" causes people to put in much more effort when in a depleted state. The theory "people who believe in willpower depletion experience it more" does explain the latter observation, but the correlational studies seem to suffer badly from reverse causality, and the experimental studies seem to involve implausibly large effects given the posited mechanism, so I suspect that something else is going on (and a number of contenders do leap to mind).

There was also a 2011 article by Kurzban that argues against glucose depletion being the cause behind the "Ego depletion" effects seen in Baumeister's studies.

I once asked a room full of about 100 neuroscientists whether willpower depletion was a thing, and there was widespread disagreement with the idea.

In which year did you do the asking?

Great question! It was in the winter of 2013, about a year and a half ago.

Related earlier posts: Kurzban et al. on opportunity cost models of mental fatigue and resource-based models of willpower, Deregulating Distraction, Moving Towards the Goal, and Level Hopping , Why Self-Control Seems (but may not be) Limited, also this comment.

From the paper discussed in the first one:

Take, for example, the reaction to our claim that the glucose version of the resource argument is false (Kurzban 2010a ). Inzlicht & Schmeichel, scholars who have published widely in the willpower-as-resource literature, more or less casually bury the model with the remark in their commentary that the “mounting evidence points to the conclusion that blood glucose is not the proximate mechanism of depletion.” ( Malecek & Poldrack express a similar view.) Not a single voice has been raised to defend the glucose model, and, given the evidence that we advanced to support our view that this model is unlikely to be correct, we hope that researchers will take the fact that none of the impressive array of scholars submitting comments defended the view to be a good indication that perhaps the model is, in fact, indefensible. Even if the opportunity cost account of effort turns out not to be correct, we are pleased that the evidence from the commentaries – or the absence of evidence – will stand as an indication to audiences that it might be time to move to more profitable explanations of subjective effort.

While the silence on the glucose model is perhaps most obvious, we are similarly surprised by the remarkably light defense of the resource view more generally. As Kool & Botvinick put it, quite correctly in our perception: “Research on the dynamics of cognitive effort have been dominated, over recent decades, by accounts centering on the notion of a limited and depletable ‘resource’” (italics ours). It would seem to be quite surprising, then, that in the context of our critique of the dominant view, arguably the strongest pertinent remarks come from Carter & McCullough, who imply that the strength of the key phenomenon that underlies the resource model – two-task “ego-depletion” studies – might be considerably less than previously thought or perhaps even nonexistent. Despite the confidence voiced by Inzlicht & Schmeichel about the two-task findings, the strongest voices surrounding the model, then, are raised against it, rather than for it. (See also Monterosso & Luo , who are similarly skeptical of the resource account.)

Indeed, what defenses there are of the resource account are not nearly as adamant as we had expected. Hagger wonders if there is “still room for a ‘resource’ account,” given the evidence that cuts against it, conceding that “[t]he ego-depletion literature is problematic.” Further, he relies largely on the argument that the opportunity cost model we offer might be incomplete, thus “leaving room” for other ideas.

This article has materially helped me over the past couple of weeks. Before, I believed that ego depletion occurred from physical, mental, or emotional effort, and I viewed it as a depletable resource. This gave me a massive excuse to slag off after I finished a task.

But the idea that willpower gets a boost as soon as the brain perceives a reward gave me a different way to look at it. Now, I focus on the reward/'hit' I get from achieving small goals. As long as I celebrate each finished task, I win, and my willpower should increase rather than decrease!

This makes me feel like a badass. If I can keep the big picture in mind, and see how each small goal advances me toward my ultimate goal, and only get more revved up everytime I finish a task, then I'm a freaking Punisher.

So thanks.

Indeed, willpower and working memory are both strongly mediated by the dorsolateral prefontal cortex, so “distraction” could just be the two functions funging against one another.

If true, this is the most important thing I have read in several months. Thank you.

How specifically to use this? When you face a situation that requires a lot of willpower, you should try to clear your working memory somehow. Meditate. Make written notes. Not just generally, but right before you do the task that requires the willpower.

I am not sure if I am not falling prey to confirmation bias here, but when I think about situations where I had emotional problems to do something at work (like: I know what I should do, but I just feel a huge distaste I cannot overcome, so I am unable to focus on the task), it usually was a situation where I was required to hold too many pieces of information in my memory (e.g. undocumented code plus dozen verbally given requirements plus random distractions). Taking a piece of paper and writing everything down helped a lot. It was not just intellectually easier, but also somehow emotionally more okay. This doesn't happen when I write my own code, probably because I code in a style that doesn't require remembering many things. -- I am still confused that people around me don't seem to have this effect, but it could be because I store things in my memory differently, so I deplete my working memory a bit faster. (This doesn't necessarily mean my memory works worse, just that it works untypically, so when people around me optimize things for how their memory works, the result doesn't work as well for me.)

Thanks for writing a post about this!

A thought on akrasia:

I wonder how much "going meta" is a serious hindrance. Attentional and decision resources are then spent at the meta level instead of the base level. Too much in the moment confusion, optimization and consideration of process, and not enough doing.

One probably shouldn't try to work on the meta level and on the base level at the same time. Go to the meta level, make decisions, write them down, plan your following tasks, schedule your next meta-level time. Then go back to the base level, and follow the plan, until you are finished or something unexpected happens. (Maybe even drink some alcohol while on the base level, to reduce your going-meta abilities. I am not completely serious about this, but a few times it really helped.)

That's about my theory as well, even down to the booze to turn off the inner Critic.

However, in any problem solving enterprise, "something unexpected happens", and the wheels start spinning.

To add an update from 2016.

Apparently some recent attempts to replicate, making sure to avoid the file drawer effect have not been able to replicate many of the older results.



"The replication team ran that same experiment at 24 different labs, including ones that translated the letter e task into Dutch, German, French, and Indonesian. Just two of the research groups produced a significant, positive effect, says study co-author Michael Inzlicht of the University of Toronto. (One appeared to find a negative effect, a reverse-depletion.) Taken all together, the experiments showed no signs whatsoever of Baumeister and Tice’s original effect."


“Meta-analyses are fucked,” Inzlicht warned me. If you analyze 200 lousy studies, you’ll get a lousy answer in the end. It’s garbage in, garbage out.

A new study by Sripada, Kessler, and Jonides (2014) found that Ritalin blocked the willpower depletion effect, and included some evidence that the amount of mindwandering might mediate the effect. I haven't taken a close look at the paper, but here's the abstract:

A recent wave of studies—more than 100 conducted over the last decade—has shown that exerting effort at controlling impulses or behavioral tendencies leaves a person depleted and less able to engage in subsequent rounds of regulation. Regulatory depletion is thought to play an important role in everyday problems (e.g., excessive spending, overeating) as well as psychiatric conditions, but its neurophysiological basis is poorly understood. Using a placebo-controlled, double-blind design, we demonstrated that the psychostimulant methylphenidate (commonly known as Ritalin), a catecholamine reuptake blocker that increases dopamine and norepinephrine at the synaptic cleft, fully blocks effort-induced depletion of regulatory control. Spectral analysis of trial-by-trial reaction times revealed specificity of methylphenidate effects on regulatory depletion in the slow-4 frequency band. This band is associated with the operation of resting-state brain networks that produce mind wandering, which raises potential connections between our results and recent brain-network-based models of control over attention.


I have a relevant blog post on models of willpower.

willpower depletion" might be nothing more than mental distraction by one of these processes

I view it as competion by different processes for a shared resource.

A robust system would have built in mechanisms for time sharing, so that one want doesn't always override the others. Different wants get allocated only so much, and then has to compete again, but at a handicap; some handicap associated with the want, some handicap associated with the justification/payoff for the want.

I'd guess that cycling different stimuli would be more effective than using the same one again and again, and that timing the reinforcement well prior to a "give up" might be effective as well. Keep "topping up" the motivation, instead of letting it run down entirely.

I suspect boredom to be another thing that can result in willpower depletion: it's hard to stay engaged in something when it's boring. It may be possible on less difficult tasks to keep going longer, but it eventually begins to drain on you (although maybe this is covered by wanting to do some other specific thing, but I suspect it was distinct in that you can be bored without having something you would rather be doing).

Maybe try having a sip of water or a bit of food if your diet permits it.

Why not have enough water so that you aren't thirsty?

If that's the problem, sure. These are just simple diagnostics. Similarly, if you lie down to read and you feel nap-ish, go actually take a nap.

This is very interesting. When I was dieting I noticed that a taste of food (but not diet coke which I drink tons of) was often enough to give me more physical and mental energy, but that it also made me feel more hungry, possibly because it set off the stomach acids ready for digestion. I wondered at the time if it could be explained by glycogen. Glycogen as I understand it is how the body stores readily available sugars that are not in the blood but where they're a lot more easily broken down than in fat. (It's also heavier than fat per calorie so it explains a lot of high early weight loss effects). I thought that maybe tasting food prompted the body to release some glycogen into blood sugar so it had the energy for digestion.

Of course this doesn't mean that distractibility isn't a Thing too. Will power is almost certainly one of those things that's 'a bit more complicated than that'...

I thought it was called 'ego' depletion because getting the ego out of the way is most of the problem. I.e. the ego is wasting too much time on the 'story of self' narrative.

While these are all interesting empirical findings, there’s a very similar phenomenon that’s much less debated and which could explain many of these observations, but I think gets too little popular attention in these discussions.

But you don't explain the findings!

I once asked a room full of about 100 neuroscientists whether willpower depletion was a thing,

I don't even know what that question is supposed to mean.

I don't even know what that question is supposed to mean.

Understanding questions isn't always trival. If you want to understand the question in depth reading Rob Baumeister's book Willpower will give you the background.