Sleep stage and personality characteristics of "natural" long and short sleepers.

A group of college freshmen that typically slept 5(1/2) hours or less per night and a group that typically slept 9(1/2) hours or more did not differ significantly on a battery of personality, scholastic, and medical measures. Compared with control subjects not selected on a sleep length criterion, electroencephalograph recordings of the short sleepers contained reduced amounts of stage 2 and rapid eye movement sleep.