Dr. Greene, when does a child start to dream? And at what age do nightmares or night terrors begin?

The truth about dreams, nightmares, and night terrors will surprise you.

Dreams have been described since the beginning of human history, but it was only in 1953 that Aserinsky and Kleitman discovered the brain wave pattern we call REM (rapid-eye-movement) sleep. During sleep, we go through four progressively deeper stages of sleep (stages 1 to 4) in which the brain is quiet but the body may move or shift.

In a separate stage, called REM sleep, the brain is highly active, but the body seems paralyzed (except for the eyes, which dart back and forth). This REM sleep is what we know as dreaming. As adults, we spend about 20% of our sleep time in REM sleep.

A preschool-aged child patters down the hall in the middle of the night to appear at her parent's bedroom door. Tears streak her face. "Mom, I've had a bad dream!" she reports. "Robbers were chasing me!"

At age 3 or 4, most children begin remarking about their dreams. In their desire to imitate adult behavior, children at that age assert (with confidence) many things that aren't quite factual. Are they really having dreams? Or might they be using their fertile imaginations to describe what they've heard others talk about, perhaps as yet another way to try to maneuver into the parents' big bed?

"I can't sleep. Can I get in?"

Alternatively, might children begin dreaming even earlier, and only start talking about it as preschoolers?

To solve this mystery, Roffwarg and associates undertook a classic study in 1966 (the associates included Dement, whose popular new book The Promise of Sleep is getting rave reviews). The research team began by studying sleep waves in newborns. The investigators believed that infants do not have REM sleep because they do not dream, but the researchers intended to discover what newborn sleep waves looked like. The team would continue to measure sleep waves throughout infancy and toddlerhood to learn when and how dreaming begins.

The startling discovery was, not only do newborns dream -- even on the first day of life -- they actually dream more than the college students in the original studies (Science, 1966; 152:604).

This study has been repeated several times, confirming and expanding our knowledge. We dream more in the first 2 weeks of life than at any other time. The visual part of the brain is more active during newborn REM sleep than during adult sleep. They seem to have more vivid visual dreams.

Infants 3 to 5 months old dream much more than infants 6 to 12 months old do. 18-month-olds dream almost twice as much as 3-year-olds do. By age 3, the amount of time spent dreaming per night is in the same range as that of young adults. As the wheel of time turns throughout life, each year we dream a little less (Science, 1966; 152:604).

If children dream from the moment that they are born, might they dream before that time? We now know that they begin to sleep at as early as 4 weeks of gestation (Electroencephalography and Clinical Neurophysiology, 1975; 38:175).