Learning while sleeping may be a trick many students try in the classroom, especially in the back rows, but scientists have shown that babies can do it. A Finnish research team has demonstrated that newborns can learn to distinguish different spoken sounds while asleep.

Babies are remarkably quick learners. They have to be to absorb all the new information that bombards them as soon as they are born. Brain scientist Marie Cheour at the University of Turku in Finland says she is impressed, for example, by how many sounds and words children recognize and speak by age one. "I was wondering how this is possible because they sleep so much during the first year of life," she says. "That made me think that perhaps it is possible that they could learn also while they are sleeping."

So Ms. Cheour and colleagues tested this notion in babies less than one week old.

As they report in the journal "Nature," they divided 45 newborns into three groups of 15 with heads wired to measure brain waves. While the three groups slept, the scientists exposed them to one hour of continuous vowel sounds. :What they heard was like "OO-OO-OO-OO-EE-OO-OO-OO-EE," says Ms. Cheour.

After this short initial session, one newborn group continued to hear those sounds overnight while the second heard different vowels and the third got just peace and quiet.

An analysis of brain wave patterns showed that the first group, the one with most exposure to the "OO-EE" vowels, was able to distinguish between them in the morning and again the next evening, while the other groups could not.

Sleep-learning has never been shown in adults. Ms. Cheour believes babies accomplish this possibly because, unlike adults, their cerebral cortex remains active at night. "The cortex is very important for learning," she says. "What we adults do when we are sleeping is we block the connection between the cortex and areas below that, and infants are not able to do that. For infants, the areas below the cortex and the cortex are more open."

Infants are believed to be capable of distinguishing all sounds that humans can utter. In other words, they are prepared to speak any language. But after hearing only certain sounds repeatedly, they soon learn to recognize only the sounds of their native tongue. Rutgers University brain scientist Paula Tallal says the new research reveals that babies do not have to be awake to do this. "What's new in this study is to show that the babies' brains are being programmed even as they sleep so that environmental input doesn't require direct attention," she says.

With the new results, Marie Cheour in Finland says it is possible that sleep training could be applied soon after birth in clinical or educational situations. "My interest is not to build some superbabies who can speak eight languages or so," she says. "I'm hoping more that in the future, we could pick up children who are at risk for learning problems and begin to train them while they are still infants before we can see any problems later on."

But Paula Tallal at Rutgers warns that this might have unintended consequences by interfering with other brain activities. Studies in adults have shown that sleep is a time when the brain processes what it has taken in during the day. "If you've got something playing constantly during the night, it might interrupt the baby's ability to integrate what it has learned the rest of the day," she says. "So I don't think we want to start jumping to conclusions that it would be good to have speech playing during the night or whatever."

Then again, the highly adaptable infant brain may be versatile enough to accomplish both processes. But it will require more research to know for sure.