With her youngest son, Nico, 3, hanging around her neck, Marina Bers greets guests in her back yard in Arlington, Mass., introducing strangers and shepherding people toward food and cider. The occasion is Sukkot, a Jewish holiday of harvest.

Bers (pronounced "Beers") and her husband, Josh, have invited people they don't know, fellow members of Temple Isaiah in Lexington, Mass.

"Isn't this great? I don't know any of these people," she says.

If there is one thing Bers, 37, likes to do, it is to create community. Typically, however, it is not the kind of community she can touch in the flesh. An assistant professor at Tufts University and an author whose new book, "Blocks to Robots," threatens to turn computer education upside down, Bers has set out to prove that computers can be our children's friends.

That flies in the face of current thinking in child development and education. For years we've been hearing that the computer detracts from young children's socialization because they don't learn to negotiate with real-live playmates; that it interferes with learning because it bypasses critical connections in the brain; and that it takes time away from physical exercise.

These concerns weigh heavily on Bers. They're why her three young children — in addition to Nico, there's Tali, 7, and Alan, 4 — each spend less than an hour a week on the computer.

The risks also are what drive Bers professionally. "Today's kids use computers so much, if we don't turn that use to a positive outcome, we are lost," she says.

Bers is pioneering technology that marries two independent disciplines — child development and computer technology. From the former, she brings the widely accepted tradition of Jean Piaget, which posits that children learn best by interacting with their world. From her mentor at Massachusetts Institute of Technology, Seymour Papert, comes the theory known as constructionism, that if children create their own technology they will learn more than if they simply swallow information technology spits out.

The software she created is called Zora. Children's Hospital Boston is using it in a pilot project where 22 transplant patients, ages 11 to 16, log on daily from around the country to build a virtual community.

Consider the population: They are at a stage of development where fitting in is all-important. As transplant patients, they must take medicines to stay alive. The medications can have side effects, including physical ones, so many of them eschew their drugs.

Zora provides common ground, an online city where each teen creates a three-dimensional house and fills it with items he loves, such as family photos, or items he covets, such as fancy cars. Some houses contain movies and audio clips.

A teen also chooses an avatar, a cartoon representation that wanders the virtual world. Visiting one another's houses and the public places they create together — a town hall, a pharmacy, a school, even Gillette Stadium — they post thoughts, hopes and fears on one another's walls.

Bers named Zora after a city in a story by Italo Calvino where people find their true identities.

Another pilot of Zora called the Computer Clubhouse launched this month, connecting 110 after-school programs around the world with the idea of discovering similarities across cultural divides.

With its social connections and avatars, Zora may sound like a cross between Facebook and Second Life. But Zora has a curriculum — and not math or science, the traditional bread-and-butter of technology education. "The curriculum of Zora is to explore issues of identity, values and community," says Bers.

It happens subtly. Bers' research students monitor the site. One afternoon, a student noticed teens chatting about their transplants. The student suggested creating a place for their stories, so they built the Transplant House. Stories now cover the walls.

Joe Gonzalez-Heydrich, a child and adolescent psychiatrist at Children's Hospital who has been involved in Zora, says the initial appeal of Zora was to get teens to support one another to take their medicines.

"These were kids who loved the computer, but all they were getting on it was shoot-'em-up games where all you learn is to be callous to human suffering and not care about people," he says. "Now, they're expressing themselves in ways they never did before to people who have come to matter to them."

To learn more about Zora, visit ase.tufts.edu/devtech/clubzora.html.