When Josh Adams sees other students at Manhattan’s School of Visual Arts each plugged into an iPod, he figures they’re being antisocial.

“I feel like they’re trying to shut people out, maybe even unintentionally,” says the 18-year-old Manhattan resident.

For New York University student Dante Lima, it’s entirely intentional.

With his ear buds in place, he’s never bothered by sidewalk hucksters.

“If you want to get away from them, just start listening to your iPod,” says Lima, 20. “They don’t approach people with headphones on.”

Wearing headphones has become the modern equivalent of wearing a “Do Not Disturb” sign around one’s neck.

Perhaps that’s no surprise. The MP3 player is only the latest in a number of gadgets — starting with the Sony Walkman, leading to the cellphone and now the iPod — that give people the ability to close off the outside world.

Shoppers chat on their cellphones, stopping only to talk briefly to a cashier.

Children watch films on the car’s DVD player instead of playing license-tag bingo.

Airline passengers watch movies on laptops or answer e-mail on BlackBerries rather than chatting with the person in the next seat.

But is tuning out the rest of the world good for us?

“We’re living in a world where technology is a huge part of our lives, but it can be a blessing and a curse,” says Jacqueline Whitmore, author of “Business Class: Etiquette Essentials for Success at Work” (St. Martin’s Press, 2005).

“Some people think this technology can make us more productive,” she says. “But it’s not helping us with social skills. It’s alienating us from other people.”

Adams, who has downloaded 2,300 songs into his own iPod, admits he used the device to duck conversation in high school.

These days, he says, he’s plugged in less often.

“Being in college promotes being more social,” he says. “Now I normally listen when I’m going to school or coming home, to make the time go by. But if someone asks me something, I always answer them. I don’t have it on so loud that I can’t hear the people around me.”

Many users of portable MP3 players say the devices help them relieve stress or, particularly at work, concentrate.

If MP3 players help you tune out noisy co-workers or help you relax while waiting for a doctor’s appointment, then what’s the harm in cocooning inside your own technological bubble?

The danger, says one sociologist, is that we start losing touch with the people in our lives — even if it’s just the cashier — because we won’t get off the phone or take off headphones to exchange pleasantries.

Studies show that these mini-conversations are important to our psychological well-being.