“…Three subjects, kept awake 90 hr, reportedly did not show any remarkable performance decrements until about the 72nd hour, at which V time they began falling into involuntary micro-sleep periods after which their performance wild immediately improve. Still, many early studies on sleep deprivation failed to find significant performance decline, until a minimum of 36 hr of sleep deprivation, and often a maximum [60][61][62][63][64][65][66][67][68][69][70][71][72] In 1937, Warren and Clark (208) used addition and subtraction and colornaming tests (similar to those of Bills) to measure blo:ks, latency, and accuracy during 65 hr of sleep deprivation. Blocking was found to increase greatly after a period of prolonged sleeplessness, but the usually employed measures of error scores and RT showed no relationship to sleep loss.…”