The field of psychology has been reeling because of problems with replicability, in that studies that claim to see certain effects have later had doubts cast upon them when efforts to replicate them failed to do so. Part of the problem is of course dealing with human subjects. But one of the theories that seemed to be pretty robust was based on a study by Roy Baumenister and Dianne Tice that suggested that people have a finite reservoir of will power and that when that is depleted by using it on some tasks, then we have reduced ability to overcome new challenges until that reservoir is replenished.
This article by Daniel Engber summarizes the original study.
Baumeister and Tice stacked their fresh-baked cookies on a plate, beside a bowl of red and white radishes, and brought in a parade of student volunteers. They told some of the students to hang out for a while unattended, eating only from the bowl of radishes, while another group ate only cookies. Afterward, each volunteer tried to solve a puzzle, one that was designed to be impossible to complete.
Baumeister and Tice timed the students in the puzzle task, to see how long it took them to give up. They found that the ones who’d eaten chocolate chip cookies kept working on the puzzle for 19 minutes, on average—about as long as people in a control condition who hadn’t snacked at all. The group of kids who noshed on radishes flubbed the puzzle test. They lasted just eight minutes before they quit in frustration.
The authors called this effect “ego depletion” and said it revealed a fundamental fact about the human mind: We all have a limited supply of willpower, and it decreases with overuse. Eating a radish when you’re surrounded by fresh-baked cookies represents an epic feat of self-denial, and one that really wears you out. Willpower, argued Baumeister and Tice, draws down mental energy—it’s a muscle that can be exercised to exhaustion.
Baumeister and others went on to suggest that the reservoir of will power was like a muscle and could be replenished and strengthened by time, sweet drinks, or mental exercises.
That paper spurred a lot of other studies that supported it and seemed to indicate that it was a robust effect applicable under a wide range of conditions. It also had the benefit of plausibility, a powerful factor in determining how easily people are persuaded by a new idea. We all know how tired we feel after we have been engaged in some task that requires the use of will power and how our resistance is reduced. When I was director of the teaching center, I used to advise faculty never to make an important decision just after finishing a lecture because it is at that time that one is mentally tired and thinking lazily, and can be tempted to opt for the easy fix that can cause problems later.
But Engber says that a researcher named Evan Carter looked more closely at all the studies and was not convinced that the effect was real.
A paper now in press, and due to publish next month in the journal Perspectives on Psychological Science, describes a massive effort to reproduce the main effect that underlies this work. Comprising more than 2,000 subjects tested at two-dozen different labs on several continents, the study found exactly nothing. A zero-effect for ego depletion: No sign that the human will works as it’s been described, or that these hundreds of studies amount to very much at all.
This is a big deal.
For scientists and science journalists, this back and forth is worrying. We’d like to think that a published study has more than even odds of being true. The new study of ego depletion has much higher stakes: Instead of warning us that any single piece of research might be unreliable, the new paper casts a shadow on a fully-formed research literature. Or, to put it another way: It takes aim not at the single paper but at the Big Idea.
It will be interesting to follow this issue. Baumeister is a very well-respected researcher and he and Tice did their original research while they were at my university. I got the chance to talk about this research in some detail when he returned a few years ago to give a talk on this. He is naturally is concerned that his major work is being called into question.
Baumeister, for his part, intends to launch his own replication effort, using methods that he thinks will work. “We try to do straight, honest work, and now we have to go to square one—just to make a point that was made 20 years ago. … It’s easier to publish stuff that tears something down than it is to build something up,” he told me wearily. “It’s not an enjoyable time. It’s not much fun.”
If it’s not much fun for the people whose life’s work has been called into question, neither does it hearten skeptics in the field. “I’m in a dark place,” Inzlicht wrote on his blog earlier this week. “I feel like the ground is moving from underneath me and I no longer know what is real and what is not.”
In researching my forthcoming book on the logic of science, I will be using this episode as an example of a common phenomenon in science, of a theory taking deep root in a field and then being questioned. How its supporters react to the challenge, and how a new consensus emerges is a fascinating process.