People who are deprived from sleep lose energy and become quick-tempered. After two days without sleep, a person find that lengthy concentration becomes difficult. He can force himself to perform tasks well for short periods, he is easily distracted. He makes many mistakes, especially at routine tasks, and his attention slips at times. Every sleepless person experiences periods in which he dozes off for a few seconds or more. He falls completely asleep unless he is kept active continuously
People who go without sleep for more than three days have great difficulty thinking, seeing and hearing clearly. They have periods of hallucinations, during which they see things that do not really exist. They also confuse daydream with real life and lose track of their thoughts in the middle of a sentence