As former IMF chief Dominique Strauss-Kahn and Arnold Schwarzenegger are involved in sex scandals, one can’t help asking: What drives alpha males to keep on having affairs?

Speaking to the Observer, Dr John Gray，the author of Men Are from Mars, Women Are from Venus, explained that powerful men have higher-than-average levels of testosterone, which they seek to "top up" when their reserves become depleted. One way they do that is to have affairs. Long-term relationships generate oxytocin, dubbed the "love hormone", which encourages bonding between couples and helps to lower female stress levels. But that benefit comes at a price for alpha male partners.

"With oxytocin and alpha men, as the women's stress level goes down when she gets oxytocin from a loving monogamous relationship, the man's testosterone level is going down, so he's getting more stressed and more inclined to seek out risky behavior to push it back up again. The concept is that intimacy can lower a man's sexual drive."

He believes that is why men like Schwarzenegger are driven to risky affairs, and why women will no longer tolerate it.

Gray also points out that compared with women in the past, modern women are getting more demanding, as they want romance, communication and domestic help. So while women are obsessing over help with the housework and men are obsessing over casual sex, their relationships are being riven apart.

Gray's theories are contested by scientists who insist society, not nature, shapes gender politics, but he insists he is not saying men are enslaved by their hormones and that divides can and should be bridged. "Men are basically wired up to be polygamous but they are also wired up to be violent. We learn to sublimate these urges and to civilize the experience. If I see an attractive woman, I use my brain to remember my wife, and my arousal goes back to my wife – you train yourself with that, you control your urges. That's why I've been married for 26 years."