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Not like a Log. There is no single best position for falling asleep, though the Encyclopaedia Britannica says all humankind adopts an approximately horizontal position. This is in contrast with birds, which sleep standing on one leg, with beak tucked under wing. Most people sleep on their sides, spending more time on one than the other, and tend to bend the hips and draw up the knees a little, the better to relax. Sleeping supine is likely to cause snoring, which may wake the sleeper himself, besides disturbing others.
Though many people claim that once they fall asleep they don't move, Dr. Kleitman is emphatic: "No normal person sleeps 'like a log.' " Anyone gets uncomfortable from staying in one position while asleep, just as he would while awake. To check this, his University of Chicago researchers rigged up Rube Goldberg devices to bedsprings and got electrical recordings of sleepers' tossing and turning. The average: 20 to 60 major movements during a night's sleep.
Most people will settle gladly for a few hours a night. But how many are really necessary? For centuries there have been six, seven-and eight-hour schools. Healthy men with strong digestions, Robert Burton held, need less sleep than those with weak stomachs; sanguine and choleric men need less than the phlegmatic, and the melancholic need most of all. Thomas Edison claimed that a man needed only four or five hours of sleep a night—but he also took daytime naps. Among volunteers in scientific studies, the natural sleeping time has ranged from about six to more than nine hours, with an average of 71.
No Instant Dream. However long they sleep, many men and women have difficulty staying asleep for the desired number of hours. Mothers get the habit of sleeping "with one ear open," afraid they may miss a high-pitched cry from a child's bedroom. Men in their 40s and over are more likely to be waked by bladder pressure.
Though it has not yet been proved, it seems likely that most predawn awakenings result from dreaming. The tensions of the day that a man carries to bed with him may be damped by a nightcap or pill, only to be reactivated by dreams after the first couple of hours, when sleep is deepest. It is in the study and explanation of dreaming that sleep scientists have recently made their most dramatic progress. The stuff that has been written about dreams would fill a library, and most of it makes as much sense as "such stuff as dreams are made on." Dr. Kleitman's Chicago team determined to collect accurate data. Such brilliant students as Dr. William Dement (now at Stanford University) and Dr. Edward Wolpert (now at Chicago's Michael Reese Hospital) stuck a tiny electrode on each side of a volunteer's eye and carried the leads to a brain-wave machine (electroencephalograph) in the next room.