Are we are hardwired to cheat after 7 years?

"When something itches my dear sir, the natural tendency is to scratch."

That's what the character, Dr Brubaker told protagonist, Richard Sherman, in the iconic film, The Seven Year Itch. 

In the movie, Sherman — a middle-aged book editor — becomes tempted by a beautiful new neighbour (played by Marilyn Monroe), while his wife and son are away. 

As he slowly succumbs to elements of temptation, wining and dining Monroe's character, he's wracked with nerves and guilt as he desperately tries to control the growing urge to cheat on his wife. 

Watch: The Ashley Madison Affair Official Trailer. Post continues below.

Since the movie's release in 1955, the term 'seven-year itch' has become a commonly used idiom to describe the concept that couple's lose their spark at around the seven-year mark. 

At the same time, the propensity for infidelity also rises, according to the notion, which has since been backed, to a degree, by research. 

"There was some research in the late '90s that found that couples start noticing that they are increasingly restless and dissatisfied in their relationship at around the seven-year mark," says relationship counsellor Susan De Campo. 

"Subsequent research has found that dissatisfaction can occur at any time after about five years and particularly after the second child."

One study, published in the Journal of Sex Research, showed the likelihood of infidelity increased over time — the longer the term of the relationship, the greater the urge to cheat. When results were separated by gender, the findings differed slightly in that women's desire to cheat peaked in the middle of the relationship, then declined, whereas men's continued to increase.

Another study published in the Journal of Marriage and Family, showed women were most likely to cheat in the seventh year of marriage, but the likelihood decreased after that. While men also had a high rate of cheating at the seventh year, which also then decreased, their desire to stray increased again at the 18-year mark, peaking at the 30-year mark. 

Fascinating stuff, hey!

"All relationships change over time because we change over time," De Campo says. 

"We have career changes, family changes, physical changes, psychological changes, attitudinal changes, educational changes. All of these factors impact how our relationship changes."

If couples fail to acknowledge how these individual changes have impacted their relationship and, in particular, if the change has resulted in relationship dissatisfaction, then people can grow apart instead of growing together. That's when they might start to think about cheating. 

"Initially, the honeymoon phase means we are swept up by a cocktail of hormones like dopamine, oxytocin and endorphins... chemicals that help us to ignore any imperfections," says De Campo. 

"After a while we start to notice flaws or features that are incompatible with our own values. Couples decide to work on the differences and stay together or end the relationship. If they stay together and become deeply compatible, then they 'pay attention' to the relationship."

So, are we hardwired to chat? De Campo says, it's complicated. 

"Esther Perel says that cheating has occurred in every culture, in every period of recorded history, throughout every religion and every social structure," she says. 

But, she says, that fact shouldn't be considered a green light to cheat on your partner.

"I don't think this means we are hardwired to cheat. I believe it's more about values, familial modeling and knowing functional ways to get one's needs met. It's complicated.

"(But) infidelity can be so so destructive. It is incredibly hurtful — with the cost invariably being far greater than what could have been imagined. Even if there is some primal propensity that underpins infidelity, we all have free will — we can choose to be sexually monogamous."

Feature Image: Getty.