根据以下材料，回答问题。
People often complained about not getting "a good night's sleep", but sleeppattems differ from person to person. Most adults require six to eight hours ofsleep to function well, while others survive on only a few hours. Still, mostpeople today think of sleep as one continuous period of downtime. This is notthe way people used to sleep. According to researchers in earlier times, peopledivided sleep by first sleep a few hours, waking up, then going back to sleep.
Beforethe 18th century, people had no gas or electricity in their homes. Fire,candles, or oil lamps were the common forms of lighting. This lack ofartificial lighting in homes contributed to people's sleep patterns. It madesense for people to go to bed early. If you live in this time period,you mightbe a hard-working farmer, and you would come home, eat and quickly fall intobed exhausted. You would probably go to sleep at 9:00 or 10:00 P.M. In thisfirst period of sleep---called
firstsleep--you would typically sleep until midnight or shortly afterwards. Halfwaythrough the night during a period some call the watch, or watching period. Whenyou came out of first sleep, you would stay in bed and relax quietly. You mighttalk with a bedfellow,meditate on the day's events or the meaning of a dream,or just let your mind wander. If you enjoyed writing or drawing, you might getout of bed to write a poem or story or draw a picture.
Then youwould start to feel sleepy, so would return to bed and fall asleep again foryour second sleep. This period would continue until early morning when daylightarrived. Again, with no artificial lighting in homes, people naturally woke upearly to take advantage of sunlight.
Today,human may consider divided sleep a strange habit, but sleep researchers saythat it is actually a more natural sleep pattem. Dr. Thomas Wehr of the U.S.National Institute of Mental Health has studied human sleep. He thinks thatmodem sleep problems occur because the orderly,natural way of sleep is breakingthrough the more recent continuous sleep pattem. Wehr and other scientistsbelieve that artificial lighting has altered the way people sleep. In aresearch study, he
asked 15adults to rest and sleep in darkness for 14 hours (from 6:00 P.M. to 8:00A.M.). At first,the subjects took a few hours to get to sleep, and then slept11 hours a night. Then overtime, they switched to divided sleep. They fellasleep for about 3 or 5 hours in the evening, stay awake for an
hour oftwo, and then slept again for four hours till early morning.
Unlikethe people in the study, we modem humans generally do not practice dividedsleep.However, many of us have the experience of waking up in the middle of thenight. We usually consider this a sleeping "problem", but perhaps weshould look at it as natural behavior. Divided sleep may be the way we shouldall be sleeping. A first sleep followed by a relaxation period and a secondperiod of sleep could help all of us to beat the stress of our fast-pacedlives.