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This Feb. 2, 2012 file photo shows CIA Director David Petraeus testifying on Capitol Hill in Washington. (Cliff Owen/AP)
This Feb. 2, 2012 file photo shows CIA Director David Petraeus testifying on Capitol Hill in Washington. (Cliff Owen/AP)

Infidelity 101: Why do people cheat? Add to ...

As tales go, it’s so typically tawdry that if The Petraeus Affair were a movie there would be no need for spoiler alerts in the reviews. A powerful man fools around with a pretty woman. Inevitably, the affair is discovered. Spouses are betrayed. A contrite resignation/tearful divorce follows.

There are more prequels to this script than James Bond incarnations: Arnold, Eliot, Tiger – pick your favourite famous philandering husband. How then, could David Petraeus, commander of armies, head of the CIA, be so foolish to become the star in one more reputation-razing scandal?

That’s love for you. Or sex, to put a less romantic point on it. Mix with power, and watch a career explode with more precision than a military drone.

“We’re talking about the most powerful brain systems that humanity has ever evolved,” says Dr. Helen Fisher, a biological anthropologist at Rutgers University, who studies the science of how humans love and why they cheat. In her brain-scan research, she found that romantic love sparked activity in the same part of the brain linked to addiction. “When you are romantically in love with someone you crave them, you are highly motivated to win them, you obsessively think about them – the same traits of an addiction. People distort reality and they are willing to do dangerous things.”

Of course, Fisher is only speculating about the nature of the relationship between the retired general and his biographer, Paula Broadwell, an army reservist and anti-terrorism advisor 20 years his junior. But it’s hard to believe that Petraeus, 60, was rationally weighing the risks to his 38-year-old marriage or the potential damage to his career. His attempts to hide e-mails lacked the imagination of a besotted, tech-savvy 16-year-old. (They wrote drafts in a jointly accessible e-mail account.) And only a woman in love, Fisher observes, sends harassing e-mails to a potential competitor, as Broadwell is alleged to have done.

Heady storylines aside, infidelity is usually subject to more down-to-earth supply-and-demand constraints. Power, and not money, creates adulterers, says Dr. Marina Adshade, a UBC economist and the author of the upcoming book Dollars and Sex.

There’s no evidence to suggest that rich men cheat more than poor men – although women married to poor husbands are more likely to stray than wives of the wealthy.

A recent Dutch study of executives and managers found that 26 per cent had cheated on their partners at least once, had more affairs the higher up the ladder they rose and were more likely to say they would cheat again. Powerful people enjoy (and are tempted by) the key ingredients for infidelity: They travel a lot, they collect yes-people who look the other way, and they are more likely to assume (often accurately) that their overtures will be warmly received. They cheat, therefore, because they can. The study found the pattern to be true for both genders. As Adshade suggests, women may cheat less often then men not because they are more faithful, but because they have been traditionally less likely to hold positions of power.

To achieve power, it helps to be a risk-taker. While that’s far from a guarantee of faithlessness, a 2010 study led by researchers at Binghamton University linked a variation in the dopamine receptor gene to higher levels of promiscuity among risk-taking university students. But that’s still a long way from an adulterer’s “my-brain-made-me-do-it” defence. (Fisher has also declined requests by criminal lawyers to testify to a science-supported love addiction that might absolve a defendant of a crime of passion.)

“We are not prisoners to our biology,” says Dr. Justin Garcia, lead author of the 2010 study. But if love and lust is comparable to a snort of cocaine it does suggest a neurological factor behind the repeat pattern of prestigious men taking amazingly destructive risks for late-night pillow talk.

“I am never entirely surprised when people make what seem like really bizarre decisions in these cases,” says Garcia. “No one makes it out of love and sex alive.”

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