LONDON — It sounds like the stuff of science fiction: a new generation of drugs that make people more intelligent.

But they are precisely the kind of mind-altering substances that students and businessman could be taking in the future to pass exams and boost work performance.

Foresight, a British government think tank, believes that “cognitive enhancers” could be “as common as coffee” within a couple of decades to help a person think faster, relax, and sleep more efficiently.

The Department of Health has become so concerned about these drugs that it has asked the Academy of Medical Sciences to assess the potential impact of the substances, some of which are licensed in Britain to treat narcolepsy or acute tiredness.

They are already being bought illegally over the Internet in America by people who think the drugs will enhance their performance in the classroom and in the office.

Researchers at Cambridge University recently examined the effects of modafinil, a drug available in Britain for people who fall asleep involuntarily, and found that it dramatically improved performance.

Within two hours of taking the drug, healthy volunteers were better at remembering strings of numbers, were less impulsive, and had a better short-term memory.

AMS has already held a series of workshops across the country to gauge the public’s view. Apart from concerns over the possible long-term damage to health, it found people were generally uninformed. One woman wondered whether she would be putting her children at a disadvantage if she did not give them access to such drugs.

The AMS study, which will be published this year, follows research by the Foresight think tank published two years ago.

In addition to drugs that boost pleasure and sexual performance, the Foresight research raised the possibility of drugs that cause selective amnesia — of a bomb attack, for instance — after the discovery that drugs called beta-blockers can reduce memories of stressful situations.

The report stated: “In a world that is increasingly nonstop and competitive, the use of such substances may move from the fringe to the norm, with cognition enhancers used as coffee is today.” Other possibilities, it said, would be drug testing of children before they took exams to ensure that some did not cheat with cognitive enhancers, or “cogs.”

“The ethical debate about whether or not to use drugs to improve performance in normal schoolchildren and students will probably be resolved over the next 20 years,” said the report. “Similarly, there will be continued debate about the ethics of using cognition enhancers in the workplace.”

One problem raised by the report is that pharmaceutical industry may change its focus from drugs that treat mental health to cognitive enhancers.

Nick Hillier, an AMS spokesman, said: “We are looking at how these drugs will potentially impact on our society.

“For example, will students in the future be taking ‘smart pills’ before an exam to help them recall facts and retain information?”