Measuring IQ Points by the Cupful

I'm sitting in Small World Coffee, the place in Princeton, N.J., where locals go when they want to avoid the sterile trendiness of Starbucks, just around the corner. The place is packed with students and professors. Nobel prizewinners drop in frequently (John Nash, the mathematician hero of A Beautiful Mind, is a regular). But I'm not here for intellectual-celebrity watching. I'm here because my editor has ordered up a story on the question of whether caffeine makes you smarter. And without a latte—with three shots of espresso today instead of the regular two—I wouldn't feel equal to the task. Experience tells me that a strong dose of caffeine inevitably makes me more alert, focused, quick-witted, clever. As far as I'm concerned, the case is already closed.

That's a purely subjective assessment, but placebo-controlled laboratory experiments say exactly the same thing. Just last month Austrian scientists reported on a study showing that the equivalent of two cups of coffee boosts short-term memory significantly. And that's just the latest in a long line of tests proving that caffeine can enhance mental performance.

Indeed, there has been lots of surprisingly good news in general about caffeine and coffee. You would naturally assume that an addictive drug like caffeine—the most widely consumed psychoactive drug on the planet—must surely be bad for you, and initial studies suggested it might lead to bladder cancer, high blood pressure and other ills. More recent research has not only refuted most of those claims but also come up with some significant benefits. Caffeine appears to have some protective effect against liver damage, Parkinson's disease, diabetes, Alzheimer's, gallstones, depression and maybe even some forms of cancer. The only proven medical downside appears to be a temporary elevation in blood pressure, which is a problem only if you already suffer from hypertension. Some studies have also suggested a higher risk of miscarriage in pregnant women and of benign breast cysts, but those results are highly controversial.

While most of the findings about the effects of caffeine remain open to further testing, caffeine's boosting your brainpower has been proved beyond any reasonable doubt "As a research psychologist," says Harris Lieberman, who works in the Military Nutrition Division of the U.S. Army Research Institute of Environmental Medicine in Natick, Mass., "I use the word intelligence as an inherent trait, something permanently part of your makeup." Caffeine can't change that, Lieberman says. But what it can do, he says, is heighten your mental performance. If you're well rested, it tends to improve rudimentary brain functions, like keeping your attention focused on boring, repetitive tasks for long periods. "It also tends to improve mood," he says, "and makes people feel more energetic, generally better overall." Observes Dr. Peter Martin, professor of psychiatry and pharmacology and director of the Addiction Center at Vanderbilt University: "Attention and mood are both elements of how we focus our intellectual resources on a problem at hand."