The 8-month-old wasn't fooled when the stopwatch that had looked so interesting was covered with a cloth. He yanked the cloth away.

But research under way around the country suggests he might not have been so savvy if he hadn't yet begun to crawl.Parents know that children experience all kinds of new things once they begin to crawl: the taste of the cat's food, the allure of their sister's room.

But psychologists say crawling also seems to trigger a variety of developmental milestones babies reach between the ages of six and nine months. They learn that toys still exist even when hidden, heights can be dangerous and objects exist that have nothing to do with themselves.

Psychologists have attributed such advances to maturation of the nervous system. But the new research is finding that developmental changes don't occur before babies are mobile, even if crawling is delayed several months.

"It's nothing short of a psychological revolution," said Rosanne Kermoian, assistant professor of psychology at Reed College. "We're finding that not only are the changes very dramatic, they're also very broad.

"We think it's not crawling itself . . . but the experiences that are associated with crawling. They have to pay attention to where they are located in space so when they go room to room they don't get lost."

The research has implications for babies delayed in crawling by handicaps or injuries, Kermoian said. They don't display the developmental changes until they begin to crawl, even if that occurs several months later than average.

Infants who aren't yet crawling but get around in a walker show more of the developmental advances than those who aren't mobile at all, and those who never crawl, but go directly to walking, display the changes when they begin to walk.

"There are certain very specific areas where they are developmentally delayed," she said. ". . . If we can show where, the better we will be able to develop appropriate therapeutic intervention."

The research shows that crawling also seems to trigger babies' understanding that they aren't the center of the universe, she said.

Mobility also seems to teach babies wariness of heights and relationships between objects, Kermoian said.