At the height of the Cold War, I remember visiting a researcher who had been commissioned by the Pentagon to study vigilance levels during sleep deprivation lasting three to five days—about how long it estimated the military officers deep in some bunker would need to stay awake during World War III. Fortunately his experiment never had to be tested against hard reality, although his encouraging finding was that even after three or more sleepless nights people could pay keen attention if their motivation was high enough (but if they didn’t care, they would nod off immediately).
