At what point are you crossing the line when you invade a partner’s privacy?

When Patricia Masterson’s boyfriend broke into her email account in search of evidence that she had been cheating, she was deeply offended by the violation of her privacy. The fact that she had, indeed, been cheating hardly seemed like a good excuse.

She changed her tune 10 years later, when, married and pregnant, Masterson innocently spotted a text message on her husband’s cellphone from a woman regarding a baby. Her husband said it must have been sent to him by mistake, and Masterson, sensitive to privacy, left it alone — until a few months later, when the woman contacted Masterson through Facebook to reveal she’d recently given birth to her husband’s child.

“I became a snooper,” said Masterson, now 39, a Defense Department contractor living in northern Virginia. She tore through cellphone records and installed software to recover deleted emails, gathering all the details she could. “It was so not me; up until that point I had believed in absolute privacy.”

When, if ever, is it OK to invade a romantic partner’s privacy? Masterson and others who have perpetrated or suffered betrayal (or both) say it’s often the only way to confirm suspicions of infidelity when all else fails.

But it can take much less for people to snoop.

Thirty-three percent of dating couples and 37 percent of spouses — slightly more women than men — say they have checked their partner’s email or call history on the sly, according to a survey last year by the gadget shopping site, which queried more than 1,000 people online. Among those under 25, almost half reported snooping. Just 9 percent discovered evidence of cheating. spokeswoman Jennifer Jacobson said she doesn’t think young couples are less trusting. “It’s just that technology has made everyone’s communications highly accessible and people probably don’t see it as a violation of trust, because of how easy it is to do.”

Larry Rosen, author of “iDisorder: Understanding Our Obsession With Technology and Overcoming Its Hold on Us” (Palgrave Macmillan), said millennials raised on a culture of Facebook stalking view privacy differently from baby boomers or Gen Xers (roughly people over 35).

“For older people, the lines are clear: Private is private, public is public,” said Rosen, a research psychologist and professor at California State University at Dominguez Hills. “For younger people it’s much more murky.”

Flirting with fire

If technology has made it easier to spy, it has also made it easier to cheat, muddying what is considered appropriate relationships. Facebook invites flirting with exes, and some people never know whom their partner is texting. Is that OK? Depends on the couple. But it can get out of hand.

The ping of a saucy text message stimulates the brain’s pleasure centers, as does cocaine, and people want more, Rosen said.

He recommends people abide by a five-minute “e-waiting period” before sending an electronic communication so that they can be more clear-headed about whether it’s a good idea.

“It’s an issue of higher-level thinking versus lower-order responding,” Rosen said. “We have turned into salivating dogs, and we have to back off a bit.”

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