David Petraeus is not yourrun-of-the-mill husband with a wandering eye. He's not just anotherphilandering politician or celebrity cheater, like so many others whoseindiscretions have come to light in recent years.

He's a retiredArmy general who designed and led the military surge in Iraq and was topcommander in Afghanistan. He had been deployed much of his career untilhe was named CIA director last year. His abrupt resignation amid newsof his extramarital affair with a married Army Reserve officer brings anew wrinkle into an old story of why yet another powerful man risks somuch for a woman.

Yes, Petraeus joins the list of wayward sons:Arnold Schwarzenegger, John Edwards, Mark Sanford and Eliot Spitzer -just to name a few.

Petraeus is another, says Frank Farley, a psychologist at Temple University who studies such behavior.

Risktakers "tend to believe they control their destiny or fate," Farleysays. "The risk-taking personality has a bold quality. It's at the heartof great leadership, and sometimes it overrides what many Americanswould call common sense."

Add in a dose of entitlement, suggestsMira Kirshenbaum, clinical director of the Chestnut Hill Institute inBoston who has written books about infidelity.

"Power andsuccess give people a sense of invulnerability," she says. "A lot ofguys like Petraeus have worked awfully hard, and yes, they have a lot toshow for it, but day-to-day mostly what they face is more hard work.Where's the big reward? An affair can seem like a long-deserved perk."

Butwhat's different in the Petraeus scandal are the greater questions hisaffair raises, including national security and the potential forblackmail.

Petraeus' resignation letter, which cites "very poorjudgment," is particularly troubling to Dan Crum, a former CIA polygraphexaminer and now consultant in Fairfax, Va.

"When he said heshowed poor judgment, it minimizes the affair and characterizes it moreas a one time poor decision than an extended period of decisions tomaintain and continue the affair," he says. "It's almost like a 'Howdare you?' response. It's part of that almost arrogance - 'Who are youto question me? I'm the one giving the orders here.' "

Crum says the fact that there was an e-mail trail "demonstrates a level of arrogance and a feeling that you're above the law."

"Anybodywith even the most minimal training in covering things up or keepingthings secret would never have e-mails that can directly link back toyou. Anybody who has a concern over being caught is going to take morecaution in maintaining the secret."

But John Caughlin, aprofessor of communication at the University of Illinois atUrbana-Champaign who focuses his research on disclosure and secrecy,says there's a flip side to that argument.

"There is a sense thatif somebody goes out of their way to take extreme measures to guardinformation - in some ways that indicates a sense of shame," Caughlinsays. "He probably knew it was wrong, but maybe not that wrong."

Newresearch by sociologist Andrew London, a senior fellow at the Institutefor Veterans and Military Families at Syracuse University in New York,has found increased risk for extramarital sex among veterans. One studyonline now in the Journal of Family Issues used 1992 data from2,308 ever-married people to find that more than 32% of veteransreported extramarital sex -- about twice the rate among ever-marriednon-veterans.

A follow-up that includes data from 2010 finds"elevated odds for extramarital sex were higher among both male andfemale veterans," he says. London, the lead author, also finds thatthose who served in the military four years or longer had a particularlyhigh risk.

"We argue there could be things that predatemilitary service - like being a risk taker - that might lead someoneinto the military but also increase his likelihood of taking a riskwhile married and having an extramarital affair," he says.

Cregg Chandler of Sumter, S.C., has seen it firsthand. He retiredin 2007 after 29 years in the Air Force, including the last nine as achaplain at bases in the USA as well as overseas in Korea and Spain. Hesays infidelity appears to have escalated in recent years. That's whyhe wrote A Separation Survival Guide for Military Couples, out earlier this year. He says military life often brings stress, isolation and frustration, which can lead to infidelity.

Military separations, which are recurring and often long-term, create loneliness without the family support system.

"They have a saying in the military: 'What happens TDY(temporary duty assignment) stays TDY.' I'm not saying it's an overallmentality, but they have that saying."