The Willpower to Care About Academic Debates

Ego depletion made everyone dumber for having listened to it.

My former advisor, the late John Tooby, used to say something like, “No data will be accepted without underlying theory.”

Or something like that.¹ I don’t remember what he said exactly. But it was pretty close to that.

To academic psychologists, this idea might sound odd. Psychology is a very empirical field, which I mostly mean in a bad way. The field has historically been light on theory and obsessed with empirical observations.

Don’t get me wrong. Empirical observations are great and of course crucial to the accumulation of knowledge. But empirical observations are best used in conjunction with good theory, as philosophers like Lakatos (see footnote) have pointed out.

This post is about an academic debate in psychology which, in itself, is of interest to few. However, the debate illustrates some lessons about the field of psychology, which might be of interest to many.

Ok, here is an incredibly condensed timeline. In 1998, psychologist Roy Baumeister and colleagues published a paper that argued that when you do something effortful—eating radishes, suppressing an emotion—you subsequently become worse at another effortful task—such as solving an anagram—because some mysterious stuff gets used up in your brain when you did the first one. Thus was born “ego depletion,” as the explanation was dubbed.

In 2007, one Matthew Gailliot, in a paper co-authored with Roy Baumeister, claimed that this mysterious stuff was glucose. In response to this, I wrote a paper that came out in 2010. There, I reanalyzed the data that Gailliot sent me—he never did send me all the data, just some of it²—and I showed that his argument was undermined by his own data. A meta-analysis would later support this conclusion: “The results provided clear and consistent evidence against the glucose view of self-control...”

In 2013, I published a paper with some of my colleagues at Penn offering a different idea for how to think about the sense of effort and why it felt difficult to persist on certain tasks. Then in 2014, my friends Evan Carter and Mike McCullough, both psychologists, published a meta-analysis of the ego depletion effect, finding “an indication that the depletion effect is actually no different from zero.”

So, by 2014 it was pretty well established that ego depletion was not, in fact, a thing. But remember that scientists do not abandon a theory merely because facts contradict it. So, in 2015, the most important academic association in social psychology, the Society for Personality and Social Psychology, conferred a prestigious prize for work on… ego depletion. One of the winners, Michael Inzlicht, writes about this in a charming and self-effacing Substack post. This post is a response to his. I want to be clear that my intention isn’t to criticize. I view Mickey’s role in this as showing deep integrity and I encourage everyone to read his post and other contributions on his Substack.

In any case, as Inzlicht recounts, huge efforts to replicate the effect failed and after uncounted hundreds of studies and untold hours of time, the idea died.

Except, it didn’t. Inzlicht’s post was motivated by a paper just published, in December of 2024, by Baumeister and colleagues, celebrating the theory while conceding that “a highly vocal minority of psychologists remains skeptical of ego depletion.” (A highly vocal minority are skeptical of the geocentric model as well, I might add.) They conclude, however, that “[c]urrent evidence is sufficient to characterize ego depletion as undeniably real and indeed among the very best replicated phenomena in social psychology” (p. 4-5).

The idea refuses to die.

Theory or Methods, That is the Question

At the end of his post, Inzlicht concludes with “The Lessons We Should Learn.”

Ego depletion’s collapse isn’t just a story about one flawed theory—it’s a cautionary tale for all of science. The replication crisis has shown us how easy it is for compelling ideas to gain traction, even when the evidence is weak. Ego depletion was built on an elegant theory and many studies that appeared to work, but elegance isn’t evidence, and quantity isn’t quality…

The theory of ego depletion reminds us of the dangers of scientific overreach, the power of compelling narratives, and the importance of rigorous methods. If we’re serious about building a more robust science, we need to confront these failures head-on—and learn from them.

Here, with all due respect, I beg to differ.

Since I just quoted Inzlicht at length, I’ll quote myself. Here is what I wrote in that paper in 2010:³

From a computational perspective, a “resource” account is the wrong kind of explanation for performance decrements to begin with. No one whose computer is performing slowly would think that the fault lies in the power supply – or the fact that running Excel for five minutes drained the battery – even though no one would deny that electricity is necessary for computers. The correct explanation for changes in performance might well lie in the domain of computation.

In short, where Inzlicht sees an elegant theory, I could not disagree more. The idea that there was a mysterious élan vital that gets used up is medieval, evoking old metaphors such as those involving hydraulics. But the brain isn’t a series of pipes, and while it does need an energy source—glucose—the energy source is used the same way that energy is used in a computer: to compute. The right sort of explanation will be in the language of information-processing, not running out of stuff.

Here’s another way to think of it: when you want a computer that can do more, you don’t go out and get a bigger battery. You buy a computer with better chips. Our brains need glucose to function in the same way that a computer needs power, but the constraint on doing more stuff has to do with computational ability. Our brain does a ton of stuff, and all of it is fueled by glucose. But when we run low on sugar, why should radish-eating suffer when other systems, such as memory or vision, do not?

So my view is that the issue wasn’t really with the experiments. I mean, sure, all of the issues with experiments in psychology might well have been relevant. But that, to me, isn’t the core issue. It’s that the theory was just obviously wrong.

By 1998, the computational view of the mind was well established. (See Steven Pinker’s book, How the Mind Works, for an excellent treatment.) The human mind evolved to process information. That has been relatively uncontroversial for decades. So proposals that don’t rest on that very basic foundation should be viewed as immediately suspect. The ego depletion theory should have never made it to the experimental stage.

Again, as Tooby used to say, no data without underlying theory. One way that good theory is important is that it sharply limits your hypotheses. A huge benefit of Darwin’s theory of evolution by natural selection is that pretty much from Darwin’s time onward, any respectable hypothesis about some bit of the biological world—e.g., some trait—had to refer to how the trait led to the survival and reproduction of the individual with the trait.⁴ Right from the start, you could eliminate the idea that horses are shaped the way they are so humans can ride them. That idea might not seem like a lot now, but the fact that most people won’t even consider that possibility illustrates how pervasive the idea has become and how natural evolutionary thinking is for most of us. (Yes, most of us. Do you think the banana’s shape is good for humans, or good for banana genes?)

So, to me, the lesson isn’t about methods. Yes, there were problems as far as that goes. For all the reasons that contributed to the so-called replication crisis, we have to be very skeptical of published results in psychology, as well as in other fields. Fair enough.

But in my view, this train should never have left the station. I recall the moment that someone explained ego depletion to me. I thought that it was a joke, maybe even a way to poke fun at psychologists to show the breadth of ideas that they were willing to entertain seriously and publish in top journals. No one, I thought, really believed that you could explain willpower or a lack of willpower by referring to mysterious stuff that was not named and could not be measured that mysteriously got used up in some mysterious process. To me, the idea didn’t pass the five second test.

But social psychology didn’t just entertain the idea. It ran with it. The original paper has now been cited more than 3,500 times. The idea gave rise to a book that has 4.5 stars on 2,378 ratings on Amazon.

But the thing is, as Jerry Fodor would say, the mind doesn’t work that way. It could be that the alternative account I offered in 2013, the opportunity cost view, is wrong. It probably is. But at least it’s the right kind of explanation, referring to information processing.

From my perspective, every paper in psychology should begin by describing how the explanation offered in the paper is consistent with the theory of evolution by natural selection. Is the effect some sort of byproduct? Great, not everything has to be an adaptation. If it is a byproduct story, then what is the trait in question a byproduct of? Is the proposal adaptation? Great, there are good criteria for evaluating such claims. George Williams saw to that.

The real issue with psychology, at least the part that concerns itself with explaining decision making and social behavior, is that the field has resisted with all of its willpower the idea that explanations need to be disciplined by the evolutionary approach. I get it. I do. It’s much more fun to make stories without worrying about pesky facts. The willpower-as-reservoir was, in its own way, sort of fun. Wouldn’t it be cool if we just ran out of some sort of stuff when we ate radishes? And in other areas, ignoring the relevant facts can be useful if you’re really more interested in advocacy than science, whether from the right or from the left. For many social psychologists, their interest is in weaving stories, often of prejudice and discrimination, unburdened by what has been.

Yes, psychologists and others have used suspect methods to arrive at the conclusions they want. The ongoing remedies for these practices are very welcome and even more needed.

Having said that, to me, all of the last quarter century of work, including the massive efforts of replication and meta-analysis would have been completely unnecessary if, before publishing the original paper in 1998, the editors had stopped to ask themselves if ego depletion was consistent with what was known about the way the mind works.

If the reviewers of the original paper had just said, wait… this makes no sense, holding aside the quality of the data, twenty-five years or precious research time and research budgets could have been saved. Alas, it was not.

Sure, sometimes it makes sense to publish papers that present anomalous findings. Data that don’t fit with existing explanations can stimulate additional theory. So much the better.

But if your explanation relies on a disproven theory of the mind, well…

Or, as one might say: No extraordinary theory will be accepted without extraordinary evidence.

1. I think John was channeling the philosopher of science, Imre Lakatos, whose ideas run along these lines. In the context of this post, it’s worth mentioning this quote by Lakatos: “Scientists…do not abandon a theory merely because facts contradict it,” from "Falsification and the Methodology of Scientific Research Programmes," 1970).

2. Gailliot told me that some of the data was “corrupted.” In case you are wondering, as far as I know there was no investigation of the authors even though this would seem to be a serious broach of scientific ethics. Shrug emoji.

3. This post is not the first place that I have made this claim. For completeness, in the Edge post I linked to above, I wrote: In the 17th century, René Descartes proposed that the nervous system worked a bit like the nifty statues in the royal gardens of Saint-Germain, whose moving parts were animated by water that ran through pipes inside of them…Three centuries on, in the mid-1900's, the detritus of the hydraulic conception of behavior, now known to be luminously wrong, was strewn about here and there… indeed, Cartesian hydraulics has been revived in at least one incarnation in the scholarly literature,… the notion that there is a "reservoir" of willpower… Given how wrong Descartes was about how the mind works, it's pretty clear that this sort of idea just can't be right.

4. Yes, it’s more complex than that because of kin selection, multi-level selection, and other refinements to the theory.