It's getting huggy out there.

It requires ever less and less acquaintance with someone to be the recipient of an embrace. Among young people and certain gregarious and gestural adults, a hug has replaced the handshake as the new default greeting.

This can pose problems for the shy and the bodily circumspect. And it can blindside people who prefer to have a direct correlation between physical contact and their feelings for the other person. They were most comfortable back when the "My dance space, your dance space" rule from "Dirty Dancing" was in vogue.

These days, those guidelines have faded. The arms come at you, leaving no chance to object. Or duck. Or turn and run. All you can do is grit your teeth into a forced smile and ponder why things have changed.

According to Amy L. Best, chair of the Anthropology and Sociology Department at George Mason University, social norms have slowly been shifting the past few decades, and boundaries have fallen.

"People are much less likely to have to abide by norms of separation and distance," she said. "Think of the Emily Post 'Guide to Manners,' where there would be rules about who extends their hand first or who gets introduced first. There are still some folks who live and die by those rules. But we're much less likely to see that."

Social hierarchy has become less important. The boss no longer sits in the corner office; instead, she sits with her employees. Parents are more likely to negotiate with children rather than lay down the "because I said so" law. And when it comes to our best friends, they often serve double duty as our co-workers, making boundaries nonexistent. These changes have blurred the lines that often kept people apart.

Some observers think that the handshake has become outmoded by its overuse among the run-of-the-mill populace. Hugging, on the other hand, is a sign of being hip.

Jürgen Streeck, a professor of anthropology and communication studies at the University of Texas at Austin, said that in ages past, "whenever someone came up with a new, particularly expressive way to show respect, it would trickle down to society at large and gradually lose its expressive quality as it became more and more conventional."

Another theory comes from Mark McCormack, a British sociologist, who has suggested that our increased hugginess is attributable to declining homophobia. In March, McCormack and colleague Eric Anderson published in the journal Men and Masculinities a study of 40 college-age male heterosexual British athletes. Ninety-three percent of the young men said they were comfortable with hugging other men.

But what if the survey had been taken during cold and flu season? Some folks in the anti-hugging camp cite health risks involved with all the touching, pointing to a study published in August in the American Journal of Infection Control that found that fist bumping is the most hygienic greeting.

Hugging backlash
The aftershocks of an unwelcome hug can linger long after the embrace is over, said Peggy Drexler, a research psychologist at Cornell University.

"A male friend of mine was part of a project that he worked with a younger woman on," she said. "They got big news on the results, and there was a feeling of celebration. He went in for the hug, and she put both hands on his chest and, without saying a word, pushed him back. Every time he sees her now, it's the first thing he thinks about. The event just sits there between them like a large person in the middle airplane seat."

What can be done to reduce all this static? In an ideal world, all hug-happy people would have the self-knowledge that Aisha Tyler does. Tyler, the comedian and a host of "The Talk," knows that she is a serial hugger.

"I hug contextually inappropriately," she said. "They should hire me to go to death row to hug inmates because I'll hug anyone."

Aware of her penchant for random hugging, Tyler will sometimes pre-empt her magnanimity. "I'll say, 'I'm an inappropriate hugger, I'm coming in now.' So people can get prepared," she said.

It also would help if huggers understood the psychology of the hug-resistant. The 2009 book "Don't Be That Guy," by humorist Colin Nissan and illustrator Sean Farrell, provides a veritable Magna Carta of straight male hugging.

"When I get married, feel free to throw your arms around me," Nissan writes. "When I have a child, by all means, wrap me into your chest. These are milestones that warrant such a gesture of affection. When I come over for poker, however, don't. Don't you dare."

An accompanying chart has two columns. The column labeled Hug Me includes, "I return from combat. Someone dies. I earn a degree. I go into surgery." The Don't Hug Me column counters with, "I spring for lunch. I get hit in softball. I get over a cold. I get blackjack."

When Nissan was contacted recently to discuss the above passage, he was reluctant because of worries that the five-year-old material would sound stale today. He said that since he wrote his book, the exigencies of living in a hug-heavy world have softened him. He no longer lives in what he calls "the don't-hug-me bubble."

"I've done my time in the bubble," he said. "But the bubble has burst."
The Washington Post contributed to this report.