Like years past, this one has been a whopper for high-profile philanderers. Psychologists aren't surprised, as guys are wired to want sex, a lot, and are more likely than gals to cheat. The behavior may be particularly likely for men with power, researchers say, though they point out that despite the genetic propensity to sleep around, cheating remains a choice, not a DNA-bound destiny.

The list of powerful individuals whose marital transgressions came out this year includes Tiger Woods, David Letterman, former senator John Edwards and South Carolina Gov. Mark Sanford.

The obvious question, perhaps most perplexing when it comes to wealthy men who had beautiful wives and seemingly enviable lives: "What were they thinking?"

Turns out, they may not have been thinking consciously about the acts at all.

"I'm guessing these things don't happen at the forefront of their brain," said Scott Reynolds, assistant professor of business ethics at the University of Washington in Seattle. "They aren't things he sits down and calculates out. It's in the background."

Even if their brains did register the infidelities, high-profile philanderers have so much power and control over their lives they likely couldn't imagine getting caught, scientists say. And with past as their guide (wins on the links for Woods and the Hill for Edwards), even if they did get caught, they could control the fallout and stay on top.

Some indiscretions were more surprising than others, with Mr. Family Values — Edwards — coming to mind. The acts are not so surprising for scientists who study this stuff, however. They know that even the most upright, squeaky-clean person can have an extramarital affair, and perhaps they are more likely to do so.

"People don't necessarily practice what they preach," said Lawrence Josephs, a clinical psychologist at Adelphi University in New York. "It's not clear to what extent people's ethical values are actually running what they do or don't do."

Case in point: "The Playboy subscription rate is highest in the Bible Belt," Josephs told LiveScience.

Whatever the cause of each extramarital act, mistresses and multiple romantic partners are here to stay, scientists say.

Sowing seeds

From an evolutionary perspective, men are here to sow their seeds. They desire more sexual partners and even lower their standards when it comes to one-night stands, studies have shown. 

"Guys would naturally be more promiscuous if given the opportunity," said Daniel Kruger, a social and evolutionary psychologist at the University of Michigan's School of Public Health.

Add status and power to the mix and extramarital affairs are par for the course.

"These people are not only high in power, but also somebody like Tiger Woods is going to be traveling a lot and have a lot more opportunities to meet women," Kruger said. "Women fawn over these guys."

Guys can get a biochemical boost as levels of testosterone increase when they, say, win an election or a big tournament, Kruger said.

"It's like if they're put on top of the pedestal, they will feel these surges of power and higher levels of testosterone are associated with more promiscuous mating and with more success in attracting partners," Kruger said. "From the individual guy's perspective not only is he going to feel a greater urge, guys in general desire more sexual variety."

The illusion of control

Celebrities and big politicians can have an inflated sense of control over their lives and feelings of invincibility.

Tiger Woods "has an incredible sense of control in every aspect of his life," Reynolds said, including what tournaments he plays in, his schedule and sponsors. "Why shouldn't he be able to control who knows about his personal life and the reactions people have to it?"

This illusion of control, Reynolds added, mixed with lots of optimism can be a dangerous mix. "When he walks into a tournament he is fully optimistic that he is going to win, with his past as his cue," Reynolds said. "Why shouldn't he win this one." Reynolds said in the back of Woods' mind, he may have thought, "Of course I'm going to have a beautiful wife, and of course I'm going to be able to do these things on the side and nobody is going to find out."

Another word for this optimism might be "arrogance."

"A serious occupational hazard of being a celebrity is arrogance, to think you are better than the next guy, special, entitled, above common issues," said Joel Block, a psychologist specializing in love, relationships and sexuality. "How else to explain Tiger's reckless behavior? Did he really think that none of these women would talk about their liaisons? His fame and acclamation clouded his judgment."

Relationship trouble?

Generalizations about men and women only go so far when trying to explain unfaithful behavior. On the individual level, various other driving forces come into play, including specifics of the relationship and personalities involved.

For instance, narcissists — or those who are completely self-absorbed, relatively arrogant and have less empathy — are more likely to stray from spouses for a fling. "It's also possible that a lot of the rich and famous guys are not only high status, but they're probably fairly high on narcissism, so they basically feel entitled to affairs," Josephs said.

Some might wonder if the celebrities who got caught were having marital trouble and that motivated the cheating. Yes and no, say scientists. 

"Cheating occurs for many reasons, consequently it is difficult to make a blanket statement about a marriage based on infidelity," said Block, author of "Broken Promises, Mended Hearts: Maintaining Trust in Love Relationships" (McGraw-Hill, 2001). "For example, infidelity may be driven by a need for an ego boost or a distraction to avoid personal issues or sexual curiosity."

Some relationship reasons might include hostility toward a partner or as a means of diluting the intensity of intimacy with one's partner, Block said.

The woman's role

Like any affair, Woods and Edwards didn't go it solo. Even if the mistresses or romantic others weren't officially taken, they may have known these celebs were. So why did they jump into the sack with married men?

"If women are considering someone to have a sexual affair with — if he's not going to bring a long-term investment — it's high-quality genes," Kruger said. "Somebody like Tiger Woods, he's young and attractive and he's athletic and incredibly high status; it makes him the perfect candidate for a short-term affair."

And statistics suggest that while men do cheat more often than women, the ladies do cheat. It should be noted that the prevalence of marital infidelity and extramarital sex varies widely depending on the definition of infidelity used and the survey referenced, ranging from about 10 percent of couples to more than half. Josephs estimates that in the United States, 20 percent to 40 percent of married men cheat, and some 15 percent to 30 percent of women do the same.

But they do so for different reasons.

"When men cheat it is typically about sex," Block said in an e-mail interview. "When women cheat it is more likely a trade-off — sex in exchange for attention, emotional support and regaining the feeling of being special."

Block added, "This is not to imply that it's all about sex for men, or that it has nothing to do with sex for women, only that the drivers are usually different."

Women may have more reason not to cheat. "For women it might be even more risky to cheat, because guys are naturally suspicious. Guys have a higher tendency to be jealous and to suspect infidelity because they don't want to be cuckolded so they're going to be hypersensitive," Kruger said. Essentially, they don't want to put their resources into raising some other guy's progeny, at least from an evolutionary perspective.

High morals and hypocrisy

Cheating may seem particularly wrong when it involves someone like Edwards, who touted family values. But from what research has shown, morality doesn't preclude indiscretion. Power can make a person stricter in moral judgment of others while being less strict of their own behavior, new research suggests.

To simulate an experience of power, Joris Lammers of Tilburg University in The Netherlands and colleagues assigned roles of high-power, such as prime minister, and low-power positions, such as a civil servant, to participants. The participants were then presented with moral dilemmas. Results showed that compared with low-power individuals, high-power participants judged others more strictly for speeding, dodging taxes and keeping a stolen bike, while finding it more acceptable to engage in these behaviors themselves.

The underlying cause is three-pronged, according to the study team, which also included Tilburg University's Diederik Stapel and Adam Galinsky of the Kellogg School of Management at Northwestern University. Power makes people more egocentric, and so they focus on their own needs; power reduces a person's ability to take on the perspective of others; and power makes people feel psychologically invisible.

"They become unaware that their behavior can be observed by others," Galinsky said.

One example would be Gov. Sanford, who voted to impeach President Bill Clinton for his transgression, and then this year admitted to cheating on his wife with a woman from Argentina, Galinsky added.

The power must be legit, however. Another experiment in this study found that people who don't feel personally entitled to their power are actually harder on themselves than they are on others. The research will be published in a forthcoming issue of the journal Psychological Science.

Perhaps we don't think of extramarital affairs as moral transgressions.

"Humans are complicated," Kruger said. "For most people we don't say we're good or evil. We have these conflicting desires, because we always have all these different challenges based on differences on what would be best for our own reproductive success and that of our partners and families."

At the end of the day, it comes down to choice, Kruger says.

"As far as the personal decisions go it's not like we're forced to do this. It's not like our genes are steering the wheel. It's a choice Tiger and others have made," Kruger said.

He added, "Even though we're talking about evolutionary bases for psychology and we do have these aggregate differences I think there is what most people think of as free will. We have a choice in these matters and we aren't genetically determined to go one way or another."