A surprisingly good New York Times essay on willpower / ego depletion:
Do You Suffer From Decision Fatigue?

As it turns out, the essay is based on an upcoming Roy F. Baumeister book, "Willpower: Rediscovering the Greatest Human Strength", which will be available from Amazon in a couple of weeks (September 1, 2011) both as a hardcover and a Kindle edition.

Some quotes from the essay (italics and headings mine):


You spend the most willpower when you have to make AND implement your decisions:

which phase of the decision-making process was most fatiguing? To find out, Kathleen Vohs, a former colleague of Baumeister’s now at the University of Minnesota, performed an experiment using the self-service Web site of Dell Computers. One group in the experiment carefully studied the advantages and disadvantages of various features available for a computer — the type of screen, the size of the hard drive, etc. — without actually making a final decision on which ones to choose. A second group was given a list of predetermined specifications and told to configure a computer by going through the laborious, step-by-step process of locating the specified features among the arrays of options and then clicking on the right ones. The purpose of this was to duplicate everything that happens in the postdecisional phase, when the choice is implemented. The third group had to figure out for themselves which features they wanted on their computers and go through the process of choosing them; they didn’t simply ponder options (like the first group) or implement others’ choices (like the second group). They had to cast the die, and that turned out to be the most fatiguing task of all. When self-control was measured, they were the one who were most depleted, by far.


Willpower depletion makes you reluctant to make trade-offs:

Once you’re mentally depleted, you become reluctant to make trade-offs, which involve a particularly advanced and taxing form of decision making. In the rest of the animal kingdom, there aren’t a lot of protracted negotiations between predators and prey. To compromise is a complex human ability and therefore one of the first to decline when willpower is depleted. You become what researchers call a cognitive miser, hoarding your energy. If you’re shopping, you’re liable to look at only one dimension, like price: just give me the cheapest. Or you indulge yourself by looking at quality: I want the very best (an especially easy strategy if someone else is paying). Decision fatigue leaves you vulnerable to marketers who know how to time their sales, as Jonathan Levav, the Stanford professor, demonstrated in experiments involving tailored suits and new cars.


Willpower depletion makes you more likely to take the path of least resistance:

As they started picking features, customers would carefully weigh the choices, but as decision fatigue set in, they would start settling for whatever the default option was. And the more tough choices they encountered early in the process — like going through those 56 colors to choose the precise shade of gray or brown — the quicker people became fatigued and settled for the path of least resistance by taking the default option. By manipulating the order of the car buyers’ choices, the researchers found that the customers would end up settling for different kinds of options, and the average difference totaled more than 1,500 euros per car (about $2,000 at the time).


Testing willpower depletion in rural Indian villages:

Most of us in America won’t spend a lot of time agonizing over whether we can afford to buy soap, but it can be a depleting choice in rural India. Dean Spears, an economist at Princeton, offered people in 20 villages in Rajasthan in northwestern India the chance to buy a couple of bars of brand-name soap for the equivalent of less than 20 cents. It was a steep discount off the regular price, yet even that sum was a strain for the people in the 10 poorest villages. Whether or not they bought the soap, the act of making the decision left them with less willpower, as measured afterward in a test of how long they could squeeze a hand grip. In the slightly more affluent villages, people’s willpower wasn’t affected significantly.


Decision fatigue can be a factor in trapping people in poverty:

Spears and other researchers argue that this sort of decision fatigue is a major — and hitherto ignored — factor in trapping people in poverty. Because their financial situation forces them to make so many trade-offs, they have less willpower to devote to school, work and other activities that might get them into the middle class.


Glucose restores willpower in humans and dogs:

To establish cause and effect, researchers at Baumeister’s lab tried refueling the brain in a series of experiments involving lemonade mixed either with sugar or with a diet sweetener. The sugary lemonade provided a burst of glucose, the effects of which could be observed right away in the lab; the sugarless variety tasted quite similar without providing the same burst of glucose. Again and again, the sugar restored willpower, but the artificial sweetener had no effect. The glucose would at least mitigate the ego depletion and sometimes completely reverse it. The restored willpower improved people’s self-control as well as the quality of their decisions: they resisted irrational bias when making choices, and when asked to make financial decisions, they were more likely to choose the better long-term strategy instead of going for a quick payoff. The ego-depletion effect was even demonstrated with dogs in two studies by Holly Miller and Nathan DeWall at the University of Kentucky. After obeying sit and stay commands for 10 minutes, the dogs performed worse on self-control tests and were also more likely to make the dangerous decision to challenge another dog’s turf. But a dose of glucose restored their willpower.


Ego depletion causes activity to rise in some parts of the brain and to decline in others:

The results of the experiment were announced in January, during Heatherton’s speech accepting the leadership of the Society for Personality and Social Psychology, the world’s largest group of social psychologists. In his presidential address at the annual meeting in San Antonio, Heatherton reported that administering glucose completely reversed the brain changes wrought by depletion — a finding, he said, that thoroughly surprised him. Heatherton’s results did much more than provide additional confirmation that glucose is a vital part of willpower; they helped solve the puzzle over how glucose could work without global changes in the brain’s total energy use. Apparently ego depletion causes activity to rise in some parts of the brain and to decline in others. Your brain does not stop working when glucose is low. It stops doing some things and starts doing others. It responds more strongly to immediate rewards and pays less attention to long-term prospects.


Good decision makers structure their lives so as to conserve willpower:

“Good decision making is not a trait of the person, in the sense that it’s always there,” Baumeister says. “It’s a state that fluctuates.” His studies show that people with the best self-control are the ones who structure their lives so as to conserve willpower. They don’t schedule endless back-to-back meetings. They avoid temptations like all-you-can-eat buffets, and they establish habits that eliminate the mental effort of making choices. Instead of deciding every morning whether or not to force themselves to exercise, they set up regular appointments to work out with a friend. Instead of counting on willpower to remain robust all day, they conserve it so that it’s available for emergencies and important decisions.

“Even the wisest people won’t make good choices when they’re not rested and their glucose is low,” Baumeister points out. That’s why the truly wise don’t restructure the company at 4 p.m. They don’t make major commitments during the cocktail hour. And if a decision must be made late in the day, they know not to do it on an empty stomach. “The best decision makers,” Baumeister says, “are the ones who know when not to trust themselves.”

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the act of making the decision left them with less willpower, as measured afterward in a test of how long they could squeeze a hand grip.

Again and again, the sugar restored willpower, but the artificial sweetener had no effect.

You can see a difference in grip strength following arduous decision making, and consuming glucose restores willpower?

I am aware that cognition is not magic, but I still find these results pretty amazing!

If people's willpower is influenced by glucose levels, I wonder what willpower is like in ketosis...

Interesting question. People doing ketogenic diets tend to report a mental fog for the first two weeks. I'd like to see some of these studies repeated on ketogenic dieters who've stuck with it long enough to get past that initial fog. I wonder to what degree diets are inherently difficult to stick with, sense they both tax willpower and reduce the amount available.

Also, if I ever become a salesman, I'll make sure to do the reciprocity trick from Cialdini--but only bring diet sodas for the customer.

If I understand correctly, ketogenic diets tend to be easier to follow because you're less hungry. This squares up pretty well with my observations of my current high-fat diet.

I should chemically test whether or not I'm in ketosis though, I remember a haze, but I had assumed that it was the results of travelling, drinking, and barely sleeping (two days of bussing + ferry through the Balkans, drinking and staying up late at a wedding (and taking notes on the experience), then a sleep-free transatlantic flight before a car trip from Maryland to North Carolina...) Lots of confounding variables there.

I'd be interested to hear the results of a keto stick test, and perhaps a willpower/glucosepower test.

I'm pretty convinced that this is just a result of glucose shifting the time discounting curve. No "expendable resource" required.

I know there's at least one study that purports to show otherwise, but this explanation is so much more elegant than any other I've yet seen proposed that right now I'm defying the data until this whole area is better understood.

Is there a connection between the time discounting curve and hand grip duration?

Trading off pain/effort while gripping for...well, whatever it was that made people want to grip the handgrip in the first place. The feeling of having been helpful in the study? Personal pride at believing yourself to have high willpower?

In any case, I think the most important finding is that glucose restores willpower. When making an important decision, pop a soda. How much can this help with akrasia?

And the more tough choices they encountered early in the process — like going through those 56 colors to choose the precise shade of gray or brown — the quicker people became fatigued and settled for the path of least resistance by taking the default option.

This suggests a model of why the RPG genre is the way it is. The character customization and resource management metagame fatigues willpower, so that you take the default action of grinding rather than the non-default action of quitting the game.

Similarly, Minecraft fatigues with creative decisions such as about architectural design, and offers the default of digging for ores.

(Random drops probably also contribute to the decision to keep grinding.)

The last pair of quotes feed into an idea I've been wondering about: is sunk cost bias a useful bias? That is, it seems to me humans frequently underinvest in long-term actions; if we do so, and we are often under the control of desires or blood sugar problems, then it would make sense to continue with long-term projects - 'engage in the sunk cost bias' - if we choose to start the project while rich in willpower but then have to continue the project under less optimal conditions. A good heuristic would be to be stubborn and continue projects even if they seem bad at that moment.

Two other bits of the article are interesting in the light of sunk cost bias. Sunk cost bias, oddly enough, does not seem to appear outside humans/primates. The article points out that choosing trade-offs are the hardest decisions and ones most often engaged in by humans and the very first kind of decisions to degrade in humans; and also that the sugar seems to act not by increasing total sugar but by affecting whether short-term or long-term decision-making areas are activated. This suggests a possibility: the normal brain decision-making structures begin to break down in humans for fundamental metabolic reasons, leading to suboptimal decisions... in the absence of a 'bias' in the opposite direction.

(Baroque or adhoc? Maybe. On the other hand, a lot of mental and biological processes seem to be regulated just by making an opposing process, rather than simply reducing the over-active process.)