Another attack on the resource-based model of willpower, Michael Inzlicht, Brandon J. Schmeichel and C. Neil Macrae have a paper called "Why Self-Control Seems (but may not be) Limited" in press in Trends in Cognitive Sciences. Ungated version here.

Some of the most interesting points:

  • Over 100 studies appear to be consistent with self-control being a limited resource, but generally these studies do not observe resource depletion directly, but infer it from whether or not people's performance declines in a second self-control task.
  • The only attempts to directly measure the loss or gain of a resource have been studies measuring blood glucose, but these studies have serious limitations, the most important being an inability to replicate evidence of mental effort actually affecting the level of glucose in the blood.
  • Self-control also seems to replenish by things such as "watching a favorite television program, affirming some core value, or even praying", which would seem to conflict with the hypothesis inherent resource limitations. The resource-based model also seems evolutionarily implausible.

The authors offer their own theory of self-control. One-sentence summary (my formulation, not from the paper): "Our brains don't want to only work, because by doing some play on the side, we may come to discover things that will allow us to do even more valuable work."

  • Ultimately, self-control limitations are proposed to be an exploration-exploitation tradeoff, "regulating the extent to which the control system favors task engagement (exploitation) versus task disengagement and sampling of other opportunities (exploration)".
  • Research suggests that cognitive effort is inherently aversive, and that after humans have worked on some task for a while, "ever more resources are needed to counteract the aversiveness of work, or else people will gravitate toward inherently rewarding leisure instead". According to the model proposed by the authors, this allows the organism to both focus on activities that will provide it with rewards (exploitation), but also to disengage from them and seek activities which may be even more rewarding (exploration). Feelings such as boredom function to stop the organism from getting too fixated on individual tasks, and allow us to spend some time on tasks which might turn out to be even more valuable.

The explanation of the actual proposed psychological mechanism is good enough that it deserves to be quoted in full:

Based on the tradeoffs identified above, we propose that initial acts of control lead to shifts in motivation away from “have-to” or “ought-to” goals and toward “want-to” goals (see Figure 2). “Have-to” tasks are carried out through a sense of duty or contractual obligation, while “want-to” tasks are carried out because they are personally enjoyable and meaningful [41]; as such, “want-to” tasks feel easy to perform and to maintain in focal attention [41]. The distinction between “have-to” and “want-to,” however, is not always clear cut, with some “want-to” goals (e.g., wanting to lose weight) being more introjected and feeling more like “have-to” goals because they are adopted out of a sense of duty, societal conformity, or guilt instead of anticipated pleasure [53].

According to decades of research on self-determination theory [54], the quality of motivation that people apply to a situation ranges from extrinsic motivation, whereby behavior is performed because of external demand or reward, to intrinsic motivation, whereby behavior is performed because it is inherently enjoyable and rewarding. Thus, when we suggest that depletion leads to a shift from “have-to” to “want-to” goals, we are suggesting that prior acts of cognitive effort lead people to prefer activities that they deem enjoyable or gratifying over activities that they feel they ought to do because it corresponds to some external pressure or introjected goal. For example, after initial cognitive exertion, restrained eaters prefer to indulge their sweet tooth rather than adhere to their strict views of what is appropriate to eat [55]. Crucially, this shift from “have-to” to “want-to” can be offset when people become (internally or externally) motivated to perform a “have-to” task [49]. Thus, it is not that people cannot control themselves on some externally mandated task (e.g., name colors, do not read words); it is that they do not feel like controlling themselves, preferring to indulge instead in more inherently enjoyable and easier pursuits (e.g., read words). Like fatigue, the effect is driven by reluctance and not incapability [41] (see Box 2).

Research is consistent with this motivational viewpoint. Although working hard at Time 1 tends to lead to less control on “have-to” tasks at Time 2, this effect is attenuated when participants are motivated to perform the Time 2 task [32], personally invested in the Time 2 task [56], or when they enjoy the Time 1 task [57]. Similarly, although performance tends to falter after continuously performing a task for a long period, it returns to baseline when participants are rewarded for their efforts [58]; and remains stable for participants who have some control over and are thus engaged with the task [59]. Motivation, in short, moderates depletion [60]. We suggest that changes in task motivation also mediate depletion [61].

Depletion, however, is not simply less motivation overall. Rather, it is produced by lower motivation to engage in “have-to” tasks, yet higher motivation to engage in “want-to” tasks. Depletion stokes desire [62]. Thus, working hard at Time 1 increases approach motivation, as indexed by self-reported states, impulsive responding, and sensitivity to inherently-rewarding, appetitive stimuli [63]. This shift in motivational priorities from “have-to” to “want-to” means that depletion can increase the reward value of inherently-rewarding stimuli. For example, when depleted dieters see food cues, they show more activity in the orbitofrontal cortex, a brain area associated with coding reward value, compared to non-depleted dieters [64].

See also: 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.


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If this model is true, then that would seem to support the effectiveness of So8res' "goal hacking" strategy. If you can convince yourself that working towards the instrumental goal (eg. of "having worked out today") is a want-to task, then you would feel less depleted and could either do it longer or be better able to perform your next have-to task. Or, if you're performing these kinds of tasks after work, convincing yourself that they are "want-to" tasks could help you complete them even in your "have-to depleted" state.

However, I still can't quite shake the intuition that there is something being depleted just by doing "hard" mental work, even if it feels like a "want-to" task. Though, this proposed model does help explain how I can sometimes come home from a full day of work and get absorbed in a programming project for another 6 hours.

Thanks for posting these, Kaj. If the standard model of resource depletion is in fact wrong, then this is very important information for people to base their anti-akrasia strategies on.

Thank you for your encouragement!

And see this comment, which is a response to both your and YVLIAZ's comments.

I can see this theory working in several scenarios, despite (or perhaps rather because of) the relative fuzziness of its description (which is of course the norm in psychological theories so far). However I have personal experiences that at least at face value don't seem to be able to be explained by this theory:

During my breaks I would read textbooks, mostly mathematics and logic, but also branching into biology/neuroscience, etc. I would begin with pleasure, but if I read the same book for too long (several days) my reading speed slows down and I start flipping a couple pages to see how far it is till the next section/chapter. So to me it this seems not like a motivation shift from "have-to" to "want-to", but rather the brain's getting fatigued at parsing text/building its knowledge database, and subjectively I still want to keep reading, and advancing page by page still brings me pleasure, but there's something "biological" that keeps me back (of course everything about me is biological, but I mean it in a metaphorical way, that it feels quite distinct from the motivational system that makes me want to read).

Now I have found an easy way to snap out of it: simply switch the book/subject. Switching from math to biology/neuroscience works better than switching from math to math (e.g. algebra to topology, category theory to recursion theory, etc), but the latter can still recover some of the mental resistance built up. I don't see how this can fit in the framework of "have-to" and "want-to". Nobody's forcing me to read these books; it's purely my desire. If the majority of executive function can be explained in such a way as expounded by the paper, then I do not see how switching subject of reading can make such a big difference.

Of course I may be an outlier here, or I'm misunderstanding what constitutes "willpower" or not. Feel free to offer your opinions.

Either way, I'm glad that this is an active area of research. I'm quite interested in motivation myself.

It feels like this model would be worth combining with Kurzban et al's model, which posits that as we continue working on some task for an extended time, our brain's estimate of the marginal benefit of continuing to work on this task gradually declines, making it more likely that we will switch to doing something else.

If we furthermore combine things with this model, which posits that the amount of interest that one has for some domain is relative to one's sensitivity to feedback in that domain, then that might be a step towards figuring out why exactly some things are intrinsically motivating. People tend to have an intrinsic interest in the kinds of things where they initially felt like they could make quick progress in - possibly pushed by some kind of drive for compressing information - or where they made slow progress at first, but then learned to understand the domain better via (possibly externally enforced) determined practice. That would suggest that areas that are high on intrinsic motivation are ones where we are sensitive to the feedback and generally interested in the topic, whereas topics where we are low on intrinsic motivation (and have to rely on extrinsic motivation) are ones we are less sensitive to feedback (and which we frequently experience ourselves as being bad at). This is also compatible with Kurzban's model, in that if you get frequent feedback from doing something, then that suggests that your marginal benefit of continuing with that task is much higher than it'd be if you didn't get much feedback.

Now consider the act of reading those textbooks. It depends on how exactly you read, but reading is often a relatively low-feedback act: you just obtain new information and store it, and furthermore a dense technical text may require you to tightly focus your attention on just the text, which is exactly the kind of task with a high opportunity cost that Kurzban's model would predict to quickly "drain your reserves" (a resource metaphor seems convenient here even if it's not actually about resources). On the other hand, if you actively try to predict what's the next thing that's said in the text, draw analogies to other things that you know, etc., then that provides you with more feedback, but also requires more dedicated cognitive effort again.

Compare that with TylerJay's example of having the energy for six hours of programming after coming home from work - programming also requires a lot of attention, but it is also a very high-feedback task, where you can constantly make changes, test if the code still compiles, see if the change is working as intended, etc.

I'm not sure of where exactly something like watching TV fits in this three-way model of (interest in topic * intensity of feedback / exclusivity of cognitive effort). TV seems like the kind of task that you don't necessarily need strong cognitive focus on, but also not something that would offer much feedback, at least not if we define feedback as a two-way interaction... but that may not necessarily be the right definition to use, given that e.g. a book can plausibly give you feedback in the sense of it causing you to think about things that you otherwise wouldn't have, and giving you new ideas about related topics.

The notion of feedback also gets interesting when we consider reading fiction - I've noticed that I tend to read novels relatively quickly, but not visualizing the events very strongly, whereas a friend of mine reads much slower, I think in part because she's an eidetic visualizer who takes the time to really see the various events in her mind's eye. Our respective reading strategies might be a product of our respective sensitivities to feedback in the domain of visualizing... for me, strong and detailed visualizations take a lot of effort, so I go with the strategy that provides me with less feedback but also requires less focus, whereas for her the more rewarding strategy is to take her time, which may require more cognitive effort (though much less than it would for me) but also provides her with much richer feedback.


You might have just figured out an excellent tool to fight addictions and poor habits, at least until they become too strong. I am impressed. Quite literally this may save lives if systematized properly.

TylerJay's example is excellent, provided that it is REPL style dynamic exploratory programming, not entering 500 lines into C++ and then banging your head against a wall because why doesn't the damn thing compile. And it is no surprise that when I am bored at work that is what I do.

When I used to drive to work and back that was high feedback enough, driving is mostly fun in the short run, now commuting with the subway made my average alcohol intake worse, I down a beer or two even before starting out for home. Alcohol and drugs are addictive not simply because they make one feel good, but because they are also high feedback, every gulp, every hit has a predictable result. When I am at home, it is usual family stuff, and it is too predictable, we just talk about what happened today, play with our child etc. it is a bit boring, because there is nothing unexpected happening.

Unpredictability must be part of the equation. While dropping a nickel into a bubble gum vending machine and reliably getting a bubble gum is high feedback, it gets boring after 4. Too predictable.

Gambling research suggests that the most addictive are those processes that are less reliable - they provide a reward only in some of the time. Thus they cause excitement, that dopamine related "excited expectation and hope" thing that is so addictive.

Exploratory programming also sometimes doesn't work and that is what it makes it interesting. Without unexpected exceptions, bugs to fix it would be boring.

Basically it suggests one way to fight addictions would be to replace them with high feedback activities appropriate to the situation. Perhaps taking the subway home would be less bad if acquiring a phone of the kind games better than tetris can be played on (so some kind of a smartphone), or trying to discuss with the fam at home what happened today when nothing ever really happens, it was just a day at work / day at babycare should be replaced by taking turns in playing poker with each other and playing child games with the child when she becomes bigger and can.

Now I have found an easy way to snap out of it: simply switch the book/subject. Switching from math to biology/neuroscience works better than switching from math to math (e.g. algebra to topology, category theory to recursion theory, etc), but the latter can still recover some of the mental resistance built up. I don't see how this can fit in the framework of "have-to" and "want-to".

I do ('have-to' and 'want-to' are dynamically redefined things for a person, not statically defined things). I regard excessive repetition as dangerous*.. even on a subconscious level. So as I get into greater # of repetitions, I feel greater and greater unease, and it's an increasing struggle to keep my focus in the face of my fear. So my 'want-to' either reduces or is muted by fear. If you do not have this type of experience, obviously this does not apply.

* Burn out and overhabituation/compulsive behaviours being two notable possibilties.

Yes, so the exact definition of "have-to" and "want-to" already present some difficulties in pinpointing what exact the theory says.

In my personal experience, it's not so much "fear" than fatigue and frustration. I also don't feel that my desire to read reduces; it stays intense, but my brain just can't keep absorbing information, and I find myself keep rereading the same passages because I can't wrap my head around them.

It occurred to me that this might also be another mechanism in the "systems approach" that Scott Adams advocates. For instance, Adams writes:

In this case, my system is that I attempt to exercise five times a week around lunchtime. And I always allow myself the option of driving to the gym then turning around and going home. What I've discovered is that the routine of preparing to exercise usually inspires me to go through with it even if I didn't start out in the mood. This particular day, my body wasn't going to cooperate. No problem. The system of attempting to exercise worked as planned. I didn't have a trace of guilt about driving home. I've used this system for my entire adult life. I see exercise as a lifestyle, not an objective.

This might accomplish the task of moving things from the category of "things I ought to do" to the category of "things I want to do". If your system is that you have to go to the gym every day, but don't need to actually exercise there, then if you do exercise you're much more likely to think that you're doing it because you genuinely want to. Whereas if you did "I have to go to the gym and practice for an hour every day", it'd be much more likely that you experienced the whole thing as something that you were only doing because you had to - and thus you'd be much more likely to quit doing it.

It seems to me that it's definitely wrong to generalize from what ever was measured to self control in general.

It's also the case that things which do straightforwardly deplete (e.g. energy when you are doing physical work) tend to be compensated for (after some exercise you get better endurance).

Self-control also seems to replenish by things such as "watching a favorite television program, affirming some core value, or even praying", which would seem to conflict with the hypothesis inherent resource limitations. The resource-based model also seems evolutionarily implausible.

I think that depends on the resource. If the resource is something like entropy, then doing an activity like watching a favorite television program or praying makes sense to provide the brain and body time for deframentation.