The easy experimental answer to this question is 264 hours (about 11 days). In 1965, Randy Gardner, a 17-year-old high school student, set this apparent world-record for a science fair. Several other normal research subjects have remained awake for eight to 10 days in carefully monitored experiments. None of these individuals experienced serious medical, neurological, physiological or psychiatric problems. On the other hand, all of them showed progressive and significant deficits in concentration, motivation, perception and other higher mental processes as the duration of sleep deprivation increased. Nevertheless, all experimental subjects recovered to relative normality within one or two nights of recovery sleep. Other anecdotal reports describe soldiers staying awake for four days in battle, or unmedicated patients with mania going without sleep for three to four days.