Here is an excerpt from an article that appeared in The New York Times (September 2, 2011). It is Steven Pinker’s review of Roy F. Baumeister and John Tierney’s Willpower: Rediscovering the Greatest Human Strength, recently published by Penguin Press. To read the complete review, please click here.

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Ever since Adam and Eve ate the apple, Ulysses had himself tied to the mast, the grasshopper sang while the ant stored food and St. Augustine prayed “Lord make me chaste — but not yet,” individuals have struggled with self-control. In today’s world this virtue is all the more vital, because now that we have largely tamed the scourges of nature, most of our troubles are self-inflicted. We eat, drink, smoke and gamble too much, max out our credit cards, fall into dangerous liaisons and become addicted to heroin, cocaine and e-mail.

Nonetheless, the very idea of self-­control has acquired a musty Victorian odor. The Google Books Ngram Viewer shows that the phrase rose in popularity through the 19th century but began to free fall around 1920 and cratered in the 1960s, the era of doing your own thing, letting it all hang out and taking a walk on the wild side. Your problem was no longer that you were profligate or dissolute, but that you were uptight, repressed, neurotic, obsessive-compulsive or fixated at the anal stage of psychosexual development.

Then a remarkable finding came to light. In experiments beginning in the late 1960s, the psychologist Walter Mischel tormented preschoolers with the agonizing choice of one marshmallow now or two marshmallows 15 minutes from now. When he followed up decades later, he found that the 4-year-olds who waited for two marshmallows turned into adults who were better adjusted, were less likely to abuse drugs, had higher self-esteem, had better relationships, were better at handling stress, obtained higher degrees and earned more money.

What is this mysterious thing called self-control? When we fight an urge, it feels like a strenuous effort, as if there were a homunculus in the head that physically impinged on a persistent antagonist. We speak of exerting will power, of forcing ourselves to go to work, of restraining ourselves and of controlling our temper, as if it were an unruly dog. In recent years the psychologist Roy F. Baumeister has shown that the force metaphor has a kernel of neurobiological reality. In Willpower, he has teamed up with the irreverent New York Times science columnist John Tierney to explain this ingenious research and show how it can enhance our lives.

In experiments first reported in 1998, Baumeister and his collaborators discovered that the will, like a muscle, can be fatigued. Immediately after students engage in a task that requires them to control their impulses — resisting cookies while hungry, tracking a boring display while ignoring a comedy video, writing down their thoughts without thinking about a polar bear or suppressing their emotions while watching the scene in Terms of Endearment in which a dying Debra Winger says goodbye to her children — they show lapses in a subsequent task that also requires an exercise of willpower, like solving difficult puzzles, squeezing a handgrip, stifling sexual or violent thoughts and keeping their payment for participating in the study rather than immediately blowing it on Doritos. Baumeister tagged the effect “ego depletion,” using Freud’s sense of “ego” as the mental entity that controls the passions.

Baumeister then pushed the muscle metaphor even further by showing that a depleted ego can be invigorated by a sugary pick-me-up (though not an indistinguishable beverage containing diet sweetener). And he showed that self-control, though almost certainly heritable in part, can be toned up by exercising it. He enrolled students in regimens that required them to keep track of their eating, exercise regularly, use a mouse with their weaker hand or (one that really gave them a workout) speak in complete sentences and without swearing. After several weeks, the students were more resistant to ego depletion in the lab and showed greater self-control in their lives. They smoked, drank and snacked less, watched less television, studied more and washed more dishes.

Together with intelligence, self-control turns out to be the best predictor of a successful and satisfying life. But Baumeister and Tierney aren’t endorsing a return to a preachy puritanism in which people are enjoined to resist temptation by sheer force of will and condemned as morally irresolute when they fail. The “will” in willpower is not some mysterious “free will,” a ghost in the machine that can do as it pleases, but a part of the machine itself. Willpower consists of circuitry in the brain that runs on glucose, has a limited capacity and operates by rules that scientists can reverse-engineer — and, crucially, that can find work-arounds for its own shortcomings.

Willpower is filled with advice about what to do with your willpower. Build up its strength, the authors suggest, with small but regular exercises, like tidiness and good posture. Don’t try to tame every bad habit at once. Watch for symptoms of ego fatigue, because in that recovery period you are especially likely to blow your stack, your budget and your diet. For that matter, don’t diet in the first place, since it starves the very system that implements self-control. Learn from Ulysses and tie yourself to the mast or fill your ears with wax so temptations are blocked out or you are unable to act on them. The authors also recommend Web sites and software that can audit, broadcast, punish or pre-empt lapses of will — a godsend, in particular, to Internet junkies and other infomaniacs.

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To read the complete review, please click here.

Steven Pinker is Harvard College professor of psychology at Harvard University. His latest book, The Better Angels of Our Nature: Why Violence Has Declined, will be published next month.