No man wakes up one morning and suddenly decides that he's going to cheat on his wife. Or vice versa. It's just one of those things that happens because we spend more time at work with our colleagues, clients or business associates than with our spouses.

Often we dress up more attractively and give our best at our workplace. By the time we get home, we're so drained that there's little left to offer our better halves.

There are enough movies and books on infidelity to alert you to the signs. The lipstick on the collar, the higher credit card and phone bills, frequently staying back at work ... you cringe when you watch these predictable, age-old plots. Yet, when it happens to you, it still hits you like a tonne of bricks.

When gossip tabloids went to town with news of the brewing Brad Pitt and Angelina Jolie affair, Jennifer Aniston was either blissfully ignorant or in denial. We all know how that ended.

The most recent scandal involved the TV confession of one-time US presidential candidate John Edwards who admitted to an extra-marital affair with actress Rielle Hunter. His wife, Elizabeth, who has breast cancer, was furious but said that their marriage would survive.

But then again, they say the wife is always the last to know.

Nurse Jean Tho, 45, never saw the writing on the wall until it was too late.

"When I look back, the signs were all there. He was "going out with the boys" a lot more and talking more on the phone. He went on a diet and was tired all the time. I didn't think much of it as he was always on a diet anyway. It was also not unusual for him to come back the next morning after a drinking session," says the mother-of-four.

"He had given up drinking when our eldest son was born nine years ago. I was too busy with the kids to keep up with the socialising so I thought he was just bored. It was not until I stumbled upon a love letter from his mistress that I put the pieces together."

By which time, Tho reckons he was hankering to be caught anyway.

Love letters

She checked his e-mail and found love messages from the other woman along with numerous SMSes. Her maid reported that tuan (Sir) was always having long conversations on the phone, and Tho found stationery and matchboxes from hotels in his car boot.

"You think you would never want to be the kind of woman who goes through her husband's things. But when you're in such a situation, you do a lot of crazy stuff and put up with more than you normally would ... all in the hope that he would come back to you," says Tho, adding that she finally snapped out of her helpless stupor when he slapped her during an argument.

"I knew then he had crossed the line. That I wouldn't take him back even if he came begging," exclaims Tho, who's in the midst of divorce proceedings.

In a 1994 study by sociologist Edward Lauman, about 18 per cent of women and 24 per cent of men reported an extra-marital affair over a lifetime (livescience.com/health/080314-spitzer-follow.html).

"Men tend to focus on the sexual aspects of infidelity; women on the emotional aspects," says David Buss, professor of psychology at the University of Texas in Austin.

The most upsetting acts of infidelity from a female perspective involve the emotional ties their husbands may have formed with the significant or insignificant others. They are more likely to forgive their husbands if the affair "meant nothing" and involved no emotional intimacy, states the study.

"You notice when the husband starts wanting to have more space, time alone, spends longer hours at the office or outstation," says consultant psychologist Dr Alvin Ng.

"He becomes less interested in the wife and picks on her negative qualities. Or suddenly, he encourages her to be different, for example, "Maybe you should go out more," or "You should try a different hairstyle"."

Having said that, he maintains that you can't tar every man with the same brush as there are many hard-working men who spend long hours away from home but are faithful.

"From a clinical point of view, sometimes it could be due to immaturity on the man's part. Guys are not always clued in to the emotions of their wives. Some would rather watch football than spend time with their spouse.

"I know of a patient who told his wife, while at the altar, to speed up the ceremony as he wanted to finish his Playstation game!"

Sadly, Dr Ng feels the male stereotype still holds true in today's society - that it's all right for the man to cheat, forgivable even, but not for the woman. But then, women who do have affairs are often better at covering their tracks and are much better liars.

"It would appear that men and women have progressed differently. Men are still uni-dimensional, afraid to get in touch with their feminine side, but women have become more aggressive and masculine. They are on the prowl and unafraid to go after what they want.

"I know women (in Malaysia) who have not one, but a few affairs simultaneously. The husbands are usually older, more domesticated, and no longer into the clubbing scene. It?s like Sex in the City in real life and in this case, it's not about fulfilling emotional needs, it's for want of sexual variety and excitement," adds Dr Ng.

"It depends on the dynamics of the couples, of course, but most people are not comfortable talking about sex, and that?s another reason why people seek to whet their appetite elsewhere."

Some men get tired of having rice for dinner every night and occasionally want sushi. The same goes for a woman when it comes to sex. That's why men don't necessarily always cheat with women who are more attractive than their partners, according to infidelity expert Stephany Alexander.

Sounds like the case of Bill Clinton and his White House intern, Monica Lewinsky. The question that played on everyone's mind: didn't Hillary have an inkling of what was going on?

Woman's intuition

Shaqira, a 37-year-old sports event co-ordinator, says a wife is intuitive about such things. After being married for 13 years, it's not hard to tell when a husband has a change of heart.

"I knew something was amiss when he became very possessive about his handphone. It used to be that he would get me to reply his messages when he was busy. At the height of the affair, the calls would come at all hours, even when he was bathing, during dinner or prayer time," she says, adding that he would scold her for "interrupting" his work when she sometimes dropped by the office to surprise him for lunch.

"He took better care of his appearance, even encouraged me to go out with my own friends more, and had many meetings with "clients". He was especially nice to me and bought me branded handbags. Once, he even offered me an air-ticket to Switzerland, to "de-stress", he says. Now, why would I want to travel by myself, without my husband or children?" says Shaqira, who has three children, aged five to 10.

The last straw was when he finally brought his "client" home one evening and introduced her to Shaqira. "I knew instantly who she was even before he said anything. There was no huge row or shouting. I believe he was quietly hoping that I would accept her as the second wife," explains Shaqira, who obtained a divorce two years ago.

When a husband plays the "It's not you, it's me," card, that's when alarm bells start going off in the wife's head.

"One day, my husband dropped a bombshell and announced that he didn't love me any more. That he'd changed and our relationship was going in a different direction," says Charmaine Te, 35. "I blamed myself for spending too much time at work. Eventually, it turned out he was seeing someone else. We've worked things out since, and the whole affair was never mentioned again."

Bob, 40, who had an affair 10 years ago, confessed that he didn't think his infidelity would affect his entire family, just his wife. When she became suspicious, he denied profusely and even accused her of wrongfully accusing him. "I was so emotionally connected to the other woman. With her, I felt appreciated," he says in retrospect.

Now, thanks to cyberspace, there's a whole new aspect to adultery. Some may argue that cyber sex is not the same as having a full-fledged affair. Where do you draw the line?

Just be careful with whom you hook up with, lest you end up like Beijinger Wang Fei, whose life has been a living hell since his wife (who committed suicide) wrote about his infidelity in her online diary.