The experiment began with a large group of undergraduates performing a mentally taxing activity that involved watching a video while ignoring the text of random words scrolling on the bottom of the screen. (It takes conscious effort to not pay attention to salient stimuli.) The students were then offered some lemonade. Half of them got lemonade made with real sugar, and the other half got lemonade made with a sugar substitute. After giving the glucose time to enter the bloodstream and perfuse the brain (about fifteen minutes), Baumeister had the students make decisions about apartments. It turned out that the students who were given the drink without real sugar were significantly more likely to rely on instinct and intuition when choosing a place to live, even if that led them to choose the wrong places. [The experiments assessed this by looking at their vulnerability to the "attraction effect," which occurs when a difficult choice is swayed by the presence of an irrelevant decoy option.] The reason, according to Baumeister, is that the parts of the brain responsible for careful, rational deliberation were simply too exhausted to think. They’d needed a restorative sugar fix, and all they’d gotten was Splenda. This research can also help explain why we get cranky when we’re hungry and tired: the brain is less able to suppress the negative emotions sparked by small annoyances.
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