An admitted affair has crumbled the career of CIA Director David Petraeus, prompting the evergreen question: Why do people with so much to lose risk it all for sex?
In the last few years alone, several public figures, from former Rep. Anthony Weiner to action star and former California Gov. Arnold Schwarzenegger, have admitted to straying from their marital vows.
In Petraeus' case, a miscalculation of risk may have contributed to the decision to cheat, psychologists say.
"People tend to underestimate how quickly small risks mount up" because of repeated exposure to those risks, said Baruch Fischhoff, a professor of social and decision science at Carnegie Mellon University.
"You do something once and you get away with it — certain things you're probably going to get away with — but you keep doing them often enough, eventually the risk gets pretty high."
Even so, men can become blind to risk at the sight of an attractive woman, and from an evolutionary perspective, cheating can be a positive mechanism for ensuring gene survival, regardless of risk, scientists say.
Military affairs
Petraeus, a retired four-star general, resigned his post as CIA Director on Friday (Nov. 9), admitting to an affair with Paula Broadwell, his biographer. Twenty years the general's junior, Broadwell had close access to Petraeus for several years, but their affair reportedly did not start until after he left the military in 2011.
A West Point graduate, Broadwell is a lieutenant colonel in the U.S. Army Reserves. She reportedly bonded with Petraeus over physical activity, going on runs with him and remaining a close confidant after Petraeus' military career ended.
That time together likely contributed to the intimacy between Petraeus and Broadwell, said Frank Farley, a Temple University psychologist, just as many people begin affairs after getting close in the workplace.
Petraeus is not the first high-ranking military man to have an affair, said Farley, who is also a past president of the American Psychological Association. Famously gruff World War II general George Patton had an affair with his wife's step-niece. General Douglas MacArthur had a mistress named Isabel Rosario Cooper, whom he met in the Philippines.
And General Dwight D. Eisenhower, later president, may have had an affair with his World War II chauffeur, Kay Summersby, according to the woman's memoirs and some suggestive letters left behind after both parties died.
"The nation should not be surprised at Petraeus having an affair," Farley told LiveScience.
Leaders like Petraeus tend to be bold risk-takers, Farley said, a personality trait that is very helpful when leading soldiers into battle. The same trait may make these leaders more likely to take risks in their personal lives, as well. [10 Easy Paths to Self Destruction]
Broadwell may have some of the same risk-taking traits as the former director. In a January interview with The Charlotte Observer, Broadwell, who is also married, called herself and her husband "adventure junkies."
Risk versus reward
Still, Petraeus' 38-year marriage and his career were at stake in his decision to pursue an affair. Extramarital liaisons are especially risky for CIA employees with access to classified information, because an affair can leave the person open to blackmail.
There are also concerns that Broadwell could have gotten classified information from Petraeus. For example, in a speech in Denver in October, Broadwell brought up details about the U.S. Consulate attack in Benghazi that may not have been public knowledge, according to The Daily Beast.
With risks like that on the line, could an extramarital affair be worth it? As it turns out, men may become blind to risk when an attractive woman enters the picture. One 2008 study found that men who played blackjack after seeing beautiful female faces took more risks than men who played the game after seeing unattractive faces.
This was true if the men were highly motivated in seeking new sexual partners. The blackjack risks seemed calculated to impress potential mates, study researcher Michael Baker, now a professor at Eastern Carolina University, told LiveScience. [The Sex Quiz: Myths, Taboos & Bizarre Facts]
More germane to high-profile affairs, Baker said, the risk of losing one's career or reputation is nothing compared with the evolutionary drive to reproduce. In that sense, while embarking on an affair may seem dumb, it actually shows something called "mating intelligence."
"These individuals have these very high-status, high-power positions, and the whole idea behind why people might be motivated to get these positions is because it gives them better access to resources that could be used to increase their reproductive success and attract more mates," Baker said.
Until the last few decades, extramarital affairs wouldn't have put a crimp in the careers of high-profile men, Baker said. It's only recently that men have been subject to the consequences of infidelity. And, of course, monogamy is often a lofty ideal.
"The human race has had thousands of years of problems with monogamy," Farley said. "The problems have not been resolved."