Nearly 40% of men and 53% of women who play online games said their virtual friends were equal to or better than their real-life friends, according to a survey of 30,000 gamers conducted by Nick Yee, a recent Ph.D. graduate from Stanford University.

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On a scorching July afternoon, as the temperature creeps toward 118 degrees in a quiet suburb east of Phoenix, Ric Hoogestraat sits at his computer with the blinds drawn, smoking a cigarette. While his wife, Sue, watches television in the living room, Mr. Hoogestraat chats online with what appears on the screen to be a tall, slim redhead.

He’s never met the woman outside of the computer world of Second Life, a well-chronicled digital fantasyland with more than eight million registered "residents" who get jobs, attend concerts and date other users. He’s never so much as spoken to her on the telephone. But their relationship has taken on curiously real dimensions. They own two dogs, pay a mortgage together and spend hours shopping at the mall and taking long motorcycle rides. This May, when Mr. Hoogestraat, 53, needed real-life surgery, the redhead cheered him up with a private island that cost her $120,000 in the virtual world’s currency, or about $480 in real-world dollars. Their bond is so strong that three months ago, Mr. Hoogestraat asked Janet Spielman, the 38-year-old Canadian woman who controls the redhead, to become his virtual wife.

The woman he’s legally wed to is not amused. "It’s really devastating," says Sue Hoogestraat, 58, an export agent for a shipping company, who has been married to Mr. Hoogestraat for seven months. "You try to talk to someone or bring them a drink, and they’ll be having sex with a cartoon."

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Mr. Hoogestraat plays down his online relationship, assuring his wife that it’s only a game. While many busy people can’t fathom the idea of taking on another set of commitments, especially imaginary ones, Second Life and other multiplayer games are moving into the mainstream. With some 30 million people now involved world-wide, there is mounting concern that some are squandering, even damaging their real lives by obsessing over their "second" ones. That’s always been a concern with videogames, but a field of study suggests that the boundary between virtual worlds and reality may be more porous than experts previously imagined.