"Surveys of married adults suggest that opposites attract when it comes to emotional reactions toward spending," Wharton's Scott Rick and Deborah Small and Northwestern's Eli Finkel said in the paper.

They found that people who generally spend less than they would ideally like to spend, and those who spend more than they would like to tend to marry each other.

George Loewenstein, a professor of economics and psychology at Carnegie Mellon University, in a separate study called "Tightwads and Spendthrifts" published last year, found that the degree people feel of a "pain of paying" determines if they are a "tightwad" or a "spendthrift."

Loewenstein's study, conducted with Wharton's Rick and Carnegie Mellon doctoral student Cynthia Cryder, found that the extent to which people said they found a pain of paying strongly predicted their savings and credit card debt, but were unrelated to income.

Participants were asked to rate their degree of happiness in their marriage from 1 to 7, with 7 being the happiest. They were also asked if they had difficulty falling asleep, staying asleep, or whether they woke early without being able to return to sleep.

The researchers looked at several other factors that might contribute to sleeplessness, such as a woman's social support network, depressive symptoms, economic hardship and employment status, alcohol and caffeine consumption, presence of children in the home, sexual activity, age, and hormonal status.

Even after taking these into account, the researchers found that women with higher reported levels of happiness in marriage had a lower risk of sleep disturbances, compared to women who report less happiness in their marriages.

Men with the 334 version of the AVPR1A gene earned lower scores from their partner/wife for strength of relationship bond. They were also less likely to be married.

If they were married, they were more likely to have experienced marital problems.

Having two copies of 334 doubled the chances that men would report having had a marital crisis in the past year.

It is thought that the gene, which was carried by 40% of the men, may affect the way the brain uses vasopressin.

The same gene has been linked with autism - a condition characterised by problems with social interaction.

But my original proposal was quiet and low-key. It was just some simple heart-felt words exchanged during a quiet night at home. And while Proposal 1.0 had plenty of sentiment, it was lacking in pizazz. So I did what any Silicon Valley geek would do: I decided to upgrade to "Proposal 2.0," a new improved online version. I proposed to Leslie from inside a Google Street View panorama. I dare say that it's the first time anyone in the history of mankind has proposed marriage in quite this way, and it went live on Google Maps on August 5, 2008:

Max Kiesler's sweet tweet at 3:13 a.m. Thursday: "To @emilychang - After fifteen years of blissful happiness I would like to ask for your hand in marriage?"

Emily Chang's reply, a minute later: "@maxkiesler - yes, i do."

The proposal: "@stefsull - ok. for the rest of the twitter-universe (and this is a first, folks) - WILL YOU MARRY ME?"

Sullivan's reply: "@garazi - OMG - Ummmmm... I guess in front of the whole twitter-verse I'll say -- I'd be happy to spend the rest of my geek life with you."

"People buy into this myth of the perfect mate and how once they find them, they won't have any interest in anyone else, and that's just wrong," says Barash. "If they're a normal healthy human mammal, they're likely to be attracted to someone else on occasion. It doesn't mean that their marriage or partnership is doomed. Nor does it mean they have to act on it."

Barash says being upfront with both yourself and your partner about the fact that "attraction happens" is the best way to deal with it - although that doesn't mean completely giving in to your inner wolf.

Another possibly new development? Shameless horndoggery.

"We've found pretty consistently that the extent to which people find their attention captured by attractive members of the opposite sex really depends upon personality characteristics," says Maner. "And people who are more sexually promiscuous are much more likely to have their attention captured by attractive members of the opposite sex."

Here's the good news: Having a secret mommy crush doesn't mean you're a bad person, about to have an affair, in a bad marriage and/or that you married the wrong guy. So why do these crushes happen?

Secret crushes can make a woman feel like a woman again. It's hard to feel like your sexy self when you're constantly cleaning up dirty laundry, dirty diapers, helping the kids with homework or cooking all the time. Sometimes being a mom and wife, although terrific in countless ways, can get a woman feeling more like a servant than a supermodel.

Having a crush is really less about the other person and more about us having the feelings we want to have, i.e., like feeling alive, excited, exciting and beautiful. Sometimes crushes are motivators to do something nice for yourself, like work out or buy something pretty and new, activities that some moms have a hard time doing for themselves. Secret crushes, when not acted on, are safe, sexy yet simultaneously ego-boosting. This intoxicating feeling often happens during transitional moments in a woman's life.

So the next time you find yourself having a secret crush, just enjoy it! All it really means is that you're still alive and remember what it's like to feel like an attractive woman. Then go and use that extra zest for life to enjoy your fabulous husband and wonderful kids. Happy fantasizing!

Researchers analyzed responses from two sets of married or cohabitating couples: one group was together for one to three years, the other for four to six years.

While the researchers could not pinpoint a precise turning point - the seven-year itch, as popularized in the play and film about errant husbands, was largely a theory - they found distinct differences between the groups.

"We know the earlier ones are happier," said Prof. Kelly Musick, a University of Southern California sociologist. "The initial boost that marriage seems to provide fades over time."

Research also showed that the median duration of first marriages that end in divorce remains a little more than seven years, which means that those couples will likely spend more than half their married lives less happy than they were when they cut the first slice of wedding cake.

"Some folks start getting less happy at the wedding reception," said Larry Bumpass, a professor at the University of Wisconsin-Madison, who wrote the study with Professor Musick.

The authors, Dr Diane Gehart and Dr Eric McCollum say it is a "myth that, with enough effort we can achieve a state without suffering."

And they say healthcare professionals may not be helping the situation.

"The field of mental health perpetuates this myth with the very concept of "mental health," which implies a state without suffering," they say.

But this belief can eventually cause people to believe that with enough effort they can eliminate suffering.

And experts say this is an unrealistic aim in relationships, and striving to achieve it can lead people to feel they have failed.

Jan Parker of the Association of Family Therapy said: "The authors are right to point out that the pursuit of relationship nirvana can be potentially damaging."