Klaus Lieb, director of the clinic for psychiatry and psychotherapy at the University of Mainz, has found that around 20 percent of students and surgeons in Germany have experimented with so-called brain doping. But do these pills really help? And what about their side effects? For a study, Lieb made 40 chess players face off against a computer - with the help of ritalin, modafilin and a placebo.