Willpower

the less fortunate subjects in other groups had to spend the interval reading dull, out-of-date magazines or drinking a large, tasteless concoction of low-fat dairy glop that was rated even less enjoyable than the old magazines.
    Just as predicted by the Mardi Gras theory, the ice cream did seem to strengthen willpower by helping people perform better than expected on the next task. Fortified by the milkshake, they had more self-control than did the unlucky subjects who’d been stuck reading the old magazines. So far, so good. But it turned out that the joyless drink of glop worked just as well, which meant that building willpower didn’t require happy self-indulgence. The Mardi Gras theory looked wrong. Besides tragically removing an excuse for romping through the streets of New Orleans, the result was embarrassing for the researchers. Matthew Gailliot, the graduate student who had run the study, stood looking glumly at his shoes as he told Baumeister about the fiasco.
    Baumeister tried to be optimistic. Maybe the study wasn’t a failure. Something had happened, after all. They’d succeeded in eliminating the ego-depletion effect. The problem was that they’d succeeded too well. Even the tasteless milkshake had done the job, but how? The researchers began to consider another possible explanation for the boost in self-control. If it wasn’t the pleasure, could it be the calories?
    At first the idea seemed a bit daft. Why should drinking some low-fat dairy concoction improve performance on a lab task? For decades, psychologists had been studying performance on mental tasks without worrying about its being affected by a glass of milk. They liked to envision the human mind as a computer, focusing on the way it processed information. In their eagerness to chart the human equivalent of the computer’s chips and circuits, most psychologists neglected one mundane but essential part of the machine: the power cord.
    Chips and circuit boards are useless without a source of energy. So is the brain. It took psychologists a while to realize this, and the realization came not from computer models but from biology. The transformation of psychology based on ideas from biology was one of the major developments of the late twentieth century. Some researchers found that genes had important effects on personality and intelligence. Others began to show that sexual and romantic behavior conformed to predictions from evolutionary theory and resembled aspects of behavior in many animal species. Neuroscientists began to map out brain processes. Others found out how hormones altered behavior. Psychologists were reminded over and over that the human mind exists in a biological body.
    This newly emerging emphasis on biology made the milkshake experimenters think twice before dismissing their results. Before writing off that dairy glop, they figured, maybe they should take a look at its ingredients, and start paying attention to stories from people like Jim Turner.

Brain Fuel
    The comedian Jim Turner has played dozens of roles in films and television series, like the football-star-turned-sports-agent on HBO’s Arliss series, but his most dramatic performance was reserved for his wife. It occurred the night he had a dream in which he was responsible for righting all the world’s wrongs. It was an exhausting duty, even in a dream, but then he discovered teleportation. To travel anywhere, all he had to do was think of the place, and he’d magically appear there. He went back to his old home in Iowa, to New York, to Greece, even to the moon. When he woke up, he was convinced he still possessed this power. He generously tried to teach it to his wife by shouting over and over, “You think it, you go there and you be there!”
    His wife had a better plan. Knowing he was diabetic, she tried to get him to drink some fruit juice. He was still so crazed that he poured some of it over his face, got up, and then demonstrated his power by doing a somersault in the air and landing back on the bed. Finally, much to her relief, the juice kicked in, and he calmed down—or at least that was how it looked to his wife, as if the manic frenzy had subsided. But in fact he hadn’t been sedated. Quite the reverse: The juice’s sugar had given him extra energy.
    More precisely, the energy in the juice was converted to glucose, the simple sugar manufactured in the body from all kinds of foods, not just sweet ones. The glucose produced by digestion goes into