Should You Trust a Partner Who Cheated Before?

If you’ve ever had a messy breakup, you know that it’s never just over and done. There are dramatic fights, sweet reconciliations, doubt, betrayal, heartbreak … all the best of 90’s rom coms. But what happens when the movie has a sequel? How do you decide if you can give a relationship another try? What if there is a history of trust issues?

A Savvy Psychologist listener named Amy reached out recently to ask about a ghost from a relationship past. She wrote:

“I had a fiancé about 20 years ago who left me for another woman. We never really lost touch and now have rekindled. We have some great chemistry but I’ve always heard, ‘Once a cheater, always a cheater.’ I’m afraid the past will keep haunting me and holding me back from giving my all and completely trusting him again.”

Amy, I want you to know, first and foremost, that anyone in your situation would be having a hard time with this dilemma. There are many feelings here -- fear, hope, doubt, perhaps a touch of resentment. And many of us can relate to the uncertainty of balancing these feelings when love and betrayal are involved.

As usual, the answer is complicated. And today, I’m not going to sugar-coat anything. We’re going to be brutally evidence-based in considering this dilemma.

First, let’s boil down the question to three things we need to consider:

• How true is the age old adage, “Once a cheater, always a cheater”? What predicts whether a person will cheat again?
• How does past infidelity affect the quality of your relationship going forward?
• What else should we consider when trying to decide to rekindle a past relationship?

Now, let’s look at what psychological research has to say about these topics:

1. Infidelity is a mixed bag

In the movies, people fall into affairs by accident. A chance encounter. An irresistible glance. A touch of the fingertips. A whirlwind romance ensues -- one that nobody saw coming. If it’s the type of story with a happy ending, they either follow their heart and end up happily ever after with the new partner, or they feel terrible about their one-time mistake and it ends up strengthening their marriage.

In real life, infidelity is more predictable. About 2-4% of married people have had extramarital sex in the past 12 months. Who’s more likely to have done it is not totally random. There are actually some consistent predictors.

For example,...

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