People with no medical problems should be allowed to take a drug used to calm hyperactive children in order to improve their own brain power, a medical expert has controversially suggested.
Professor John Harris even said that preventing healthy people from enhancing their mental performance by taking Ritalin, also known as methylphenidate, was unethical.
Writing in an article on bmj.com, the bioethics professor at the University of Manchester said: "It is not rational to be against human enhancement. Humans are creatures that result from an enhancement process called evolution and moreover are inveterate self-improvers in every conceivable way."
Children who exhibit symptoms of inattention, hyperactivity and impulsiveness - known as attention deficit hyperactivity disorder (ADHD) - are routinely prescribed Ritalin to help them function in "normal" society.
Students have also been known to take the drug, which enhances study skills and boosts attention focus, in order to improve their academic performance.
However, Professor Anjan Chatterjee, from the University of Pennsylvania, said there were too many risks in taking Ritalin unless people were actually ill.
He questioned whether children at top schools would take Ritalin in "epidemic proportions" and if people such as pilots, police officers and on-call doctors would be pressurised into taking the drug to perform better.