A veritable goldmine of relevant material in John Tierney’s “Do You Suffer From Decision Fatigue?” in The NY Times Magazine this past week. We’ve written about “ego depletion” a number of times before – the verified psychological phenomenon of self-control being a depletable resource – but Tierney does a fine job of drawing out the implications, both positive and negative. Of particular note is the way compassion so automatically flows out of an understanding of the human will as having (severe) limitations. It comes through loud and clear, especially when he talks about how trade-off-related decision fatigue informs the cycle of poverty in this country, a page taken almost directly from the Grace in Practice section on the bondage of the will. Self-righteousness being another casualty of these breakthroughs.

Of course, while Tierney focuses on how we can make the best of our limited stores of willpower, we might see this as further confirmation that the human agency operates under uncomfortably strict parameters, that the very idea of “counteracting it” seems a bit absurd (being “saved from it,” perhaps less so). Life, in other words, is not (and cannot be) a matter of making healthy decisions but of coming to terms with our inability to do so. The paragraphs describing the desire experiment are undeniably amusing:

Decision fatigue can make quarterbacks prone to dubious choices late in the game and C.F.O.’s prone to disastrous dalliances late in the evening. It routinely warps the judgment of everyone, executive and nonexecutive, rich and poor — in fact, it can take a special toll on the poor. Yet few people are even aware of it, and researchers are only beginning to understand why it happens and how to counteract it.

Decision fatigue helps explain why ordinarily sensible people get angry at colleagues and families, splurge on clothes, buy junk food at the supermarket and can’t resist the dealer’s offer to rustproof their new car. No matter how rational and high-minded you try to be, you can’t make decision after decision without paying a biological price. It’s different from ordinary physical fatigue — you’re not consciously aware of being tired — but you’re low on mental energy. The more choices you make throughout the day, the harder each one becomes for your brain, and eventually it looks for shortcuts, usually in either of two very different ways. One shortcut is to become reckless: to act impulsively instead of expending the energy to first think through the consequences. (Sure, tweet that photo! What could go wrong?) The other shortcut is the ultimate energy saver: do nothing. Instead of agonizing over decisions, avoid any choice. Ducking a decision often creates bigger problems in the long run, but for the moment, it eases the mental strain. You start to resist any change, any potentially risky move — like releasing a prisoner who might commit a crime. So the fatigued judge on a parole board takes the easy way out, and the prisoner keeps doing time.

Decision fatigue is the newest discovery involving a phenomenon called ego depletion, a term coined by the social psychologist Roy F. Baumeister in homage to a Freudian hypothesis. Freud speculated that the self, or ego, depended on mental activities involving the transfer of energy. He was vague about the details, though, and quite wrong about some of them (like his idea that artists “sublimate” sexual energy into their work, which would imply that adultery should be especially rare at artists’ colonies).

These experiments demonstrated that there is a finite store of mental energy for exerting self-control. When people fended off the temptation to scarf down M&M’s or freshly baked chocolate-chip cookies, they were then less able to resist other temptations. When they forced themselves to remain stoic during a tearjerker movie, afterward they gave up more quickly on lab tasks requiring self-discipline, like working on a geometry puzzle or squeezing a hand-grip exerciser. Willpower turned out to be more than a folk concept or a metaphor. It really was a form of mental energy that could be exhausted. The experiments confirmed the 19th-century notion of willpower being like a muscle that was fatigued with use, a force that could be conserved by avoiding temptation. To study the process of ego depletion, researchers concentrated initially on acts involving self-control ­— the kind of self-discipline popularly associated with willpower, like resisting a bowl of ice cream. They weren’t concerned with routine decision-making, like choosing between chocolate and vanilla, a mental process that they assumed was quite distinct and much less strenuous. Intuitively, the chocolate-vanilla choice didn’t appear to require willpower.

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.

Shopping can be especially tiring for the poor, who have to struggle continually with trade-offs. 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. Because they had more money, they didn’t have to spend as much effort weighing the merits of the soap versus, say, food or medicine.

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. It’s hard to know exactly how important this factor is, but there’s no doubt that willpower is a special problem for poor people. Study after study has shown that low self-control correlates with low income as well as with a host of other problems, including poor achievement in school, divorce, crime, alcoholism and poor health. Lapses in self-control have led to the notion of the “undeserving poor” — epitomized by the image of the welfare mom using food stamps to buy junk food — but Spears urges sympathy for someone who makes decisions all day on a tight budget. In one study, he found that when the poor and the rich go shopping, the poor are much more likely to eat during the shopping trip. This might seem like confirmation of their weak character — after all, they could presumably save money and improve their nutrition by eating meals at home instead of buying ready-to-eat snacks like Cinnabons, which contribute to the higher rate of obesity among the poor. But if a trip to the supermarket induces more decision fatigue in the poor than in the rich — because each purchase requires more mental trade-offs — by the time they reach the cash register, they’ll have less willpower left to resist the Mars bars and Skittles. Not for nothing are these items called impulse purchases.

The discoveries… help explain why dieting is a uniquely difficult test of self-control — and why even people with phenomenally strong willpower in the rest of their lives can have such a hard time losing weight. They start out the day with virtuous intentions, resisting croissants at breakfast and dessert at lunch, but each act of resistance further lowers their willpower. As their willpower weakens late in the day, they need to replenish it. But to resupply that energy, they need to give the body glucose. They’re trapped in a nutritional catch-22:

1. In order not to eat, a dieter needs willpower.

2. In order to have willpower, a dieter needs to eat.

Even if we could all afford to work half-days, we would still end up depleting our willpower all day long, as Baumeister and his colleagues found when they went into the field in Würzburg in central Germany. The psychologists gave preprogrammed BlackBerrys to more than 200 people going about their daily routines for a week. The phones went off at random intervals, prompting the people to report whether they were currently experiencing some sort of desire or had recently felt a desire. The painstaking study, led by Wilhelm Hofmann, then at the University of Würzburg, collected more than 10,000 momentary reports from morning until midnight.

Desire turned out to be the norm, not the exception. Half the people were feeling some desire when their phones went off — to snack, to goof off, to express their true feelings to their bosses — and another quarter said they had felt a desire in the past half-hour. Many of these desires were ones that the men and women were trying to resist, and the more willpower people expended, the more likely they became to yield to the next temptation that came along. When faced with a new desire that produced some I-want-to-but-I-really-shouldn’t sort of inner conflict, they gave in more readily if they had already fended off earlier temptations, particularly if the new temptation came soon after a previously reported one.

The results suggested that people spend between three and four hours a day resisting desire. Put another way, if you tapped four or five people at any random moment of the day, one of them would be using willpower to resist a desire. The most commonly resisted desires in the phone study were the urges to eat and sleep, followed by the urge for leisure, like taking a break from work by doing a puzzle or playing a game instead of writing a memo. Sexual urges were next on the list of most-resisted desires, a little ahead of urges for other kinds of interactions, like checking Facebook. To ward off temptation, people reported using various strategies. The most popular was to look for a distraction or to undertake a new activity, although sometimes they tried suppressing it directly or simply toughing theirway through it. Their success was decidedly mixed…

“The best decision makers,” Baumeister says, “are the ones who know when not to trust themselves.”

End-note: Tierney and Baumeister have written a book on the subject which comes out next month, the not-so-sympathetically titled Willpower: Rediscovering the Greatest Human Strength.