“I think the analogy with sports doping is really misleading, because in sports it’s all about competition, only about who’s the best runner or home run hitter,” said Martha Farah, director of the Center for Cognitive Neuroscience at the University of Pennsylvania. “In academics, whether you’re a student or a researcher, there is an element of competition, but it’s secondary. The main purpose is to try to learn things, to get experience, to write papers, to do experiments. So in that case if you can do it better because you’ve got some drug on board, that would on the face of things seem like a plus.”

She and other midcareer scientists interviewed said that, as far as they knew, very few of their colleagues used brain-boosting drugs regularly. Many have used Provigil for jet lag, or even to stay vertical for late events. But most agreed that the next generation of scientists, now in graduate school and college, were more likely to use the drugs as study aids and bring along those habits as they moved up the ladder.

Surveys of college students have found that from 4 percent to 16 percent say they have used stimulants or other prescription drugs to improve their academic performance  usually getting the pills from other students.

“Suppose you’re preparing for the SAT, or going for a job interview  in those situations where you have to perform on that day, these drugs will be very attractive,” said Dr. Barbara Sahakian of Cambridge, a co-author with Sharon Morein-Zamir of the recent essay in Nature. “The desire for cognitive enhancement is very strong, maybe stronger than for beauty, or athletic ability.”

Jeffrey White, a graduate student in cell biology who has attended several institutions, said that those numbers sounded about right. “You can usually tell who’s using them because they can be angry, testy, hyperfocused, they don’t want to be bothered,” he said.

Mr. White said he did not use the drugs himself, considering them an artificial shortcut that could set people up for problems later on. “What happens if you’re in a fast-paced surgical situation and they’re not available?” he asked. “Will you be able to function at the same level?”

Yet such objections  and philosophical concerns  can vaporize when students and junior faculty members face other questions: What happens if I don’t make the cut? What if I’m derailed by a bad test score, or a mangled chemistry course?