RENEE MONTAGNE, Host:
It's not surprising that people went to sleep earlier in the days before electric light. There's evidence that they also slept much differently than we do today. People may have slept in shifts, as most animals do.
STEVE INSKEEP, Host:
In the '90s he observed sleep patterns of adults. They were isolated in a room with 14-hour-long periods of darkness. That resembles a nighttime without electric lights.
MONTAGNE: Dr. Wehr discovered that participants began to sleep in two phases. First, they'd sleep for about four hours; then they'd be awake for one to three hours; then four more hours of sleep. Participants described the waking interval as a very tranquil time of quiet attentiveness.
INSKEEP: That's when they produced a morning program. Historians have found people referring to first sleep and second sleep as far back as Homer. Wehr suggests that the use of modern lighting has made us chronically sleep deprived.
MONTAGNE: Some of us need to be taught how to get a good night's sleep. If you're one of those people, we've got some lessons for you at npr.org/yourhealth.