Women don't cheat for the same reasons as men. Here's why some women stray and what you can do.
We've yet to find out why Kristen Stewart cheated on R-Patz. But we do know that, while men still cheat more than women, the gap is closing. We also know that men and women often cheat for different reasons.
In fact, women rarely stray because they find someone better looking or more successful than the men they're with. In many cases it's what men do (or don't do) that drives their partners into the arms of other men.
Here are the mistakes men make that explain (though don't justify) why women cheat, so you can make sure you don't make them.
She's not necessarily bored of you or even your sex life. But she is bored of her day-to-day existence, and that can make her more prone to seeking excitement elsewhere.
In her book Daring Wives, clinical psychologist Frances Cohen Praver describes a woman called Debra who seems to have it all.
She has a handsome, successful husband, a lovely home and plenty of free time. But "she feels trapped, bored, powerless, and lonely." Her husband is too busy trying to become even more successful to notice Debra's increasing despondency.
So when the chance arises, she has an affair, for the excitement and the break from her mundane day-to-day existence.
So what does a bored partner have to do with you? Well, nothing, if you're offering her all the support you can. Being in a relationship means being there for the bad times, and women with supportive partners are unlikely to be driven to desperate measures. But if you've ignored her pleas for help, or treat her problems as an irrelevance, she may start looking for excitement elsewhere.
She's getting revenge
You cheated on her, so she exacts revenge. This one's not rocket science. Don't cheat and don't get cheated on.
She's in crisis mode
When things are looking down, some women might respond by seeking the temporary high of illicit love making. Not consciously, perhaps, but a crisis point can leave women (as well as men) more psychologically open to the possibility of infidelity.
That crisis can be turning 30 or 40. It can be losing a good job or a major falling out with a best friend. Your job is to be there for her during those dark times, and to keep reassuring her about her worth, beauty, competence or whatever it might be. During crisis times you ignore her pain at your peril.
She can't reach you
It may be work, or family, or your football team (it shouldn't really be your football team) but your misery can be infectious. Some men respond to their own problems - even if they have nothing to do with the relationship - by withdrawing, emotionally, from their partners. Metaphorically they find a cave and creep inside.
Don't pull up the emotional drawbridge. Whatever the root cause, her inability to reach you and to help will make her think you have a problem with her and with your relationship. If it carries on too long, she may subconsciously start to regard infidelity not as cheating but as moving on, and preparing for the inevitable break-up your behaviour seems to foretell.
Instead, keep her informed. Keep letting her know how you feel. Keep her in the loop and she will keep thinking that she's a valuable part of your life.
She wants out
Some women - like some men - can be pretty cowardly, especially when it comes to breaking up. So she may avoid 'The Conversation' and have an affair instead. She may even want to set another relationship up before she leaves the present one, to avoid the heartache of being alone.
At this stage, there isn't much you can do, and given her behaviour, you might be happy to put this one down to experience. It might be worth musing on how you got to this unhappy point though, just to make sure it doesn't happen again in the future.
What should we take away from this?
The point of all this is that she's unlikely to cheat because she just can't resist that hunk at the bar, or she wants better intercourse, or somebody's just a bit smoother than you. If your relationship was serious, it's probably down to communication, and her sense - justified or not - that she is no longer your priority. If that's the case, there's plenty you can do to make sure infidelity never strikes at the heart of your relationship.