Why do some relationships look so promising, yet dissolve over time? And why do others, whose partners seem hopelessly mismatched, grow stronger?

Much research has tried to identify the individual characteristics that make for a successful relationship, including how couples deal with conflict or communicate. All shed some light on what may underlie relationship success.

But a new study of over 11,000 couples reveals a key ingredient that’s easily overlooked or ignored — and it’s the major predictor of relationship happiness, romantic intimacy, and connection.

It’s not how well two prospective partners matched up on a dating site. It’s not about personality features, personal history, or interests. These do play a role in predicting long-term relationship success, but the study found they play a much smaller role than one might think. 

What’s the “Secret?”   

Simply put, the research found that strongest predictor is the kind of relationship the partners create together, over time. That is, the quality of the relationship they experience transcends individual traits or characteristics in predicting the couple’s happiness over time.

The study, from Canada’s Western University, was based on a different kind of analysis of information from 43 studies of the 11,000 couples. As lead author Samantha Joel stated, “It suggests that the person we choose is not nearly as important as the relationship we build.” It's the overall way the partners relate to each other. The research shows, she adds, that "the dynamic that you build with someone — the shared norms, the in-jokes, the shared experiences — is so much more than the separate individuals who make up that relationship." 

The study looked at individual characteristics that you might assume to be the most important predictors of a happy relationship, like the individual partner’s feelings about their life situation, their tendency toward anxiety or depression, their attachment pattern, or whether their parents had a stable marriage or divorce. Those factors can have a negative impact on the relationship, of course. But the research found that they were much less significant for happiness than the actual pattern of the ongoing relationship — that is, how they interact, and how each feels about the interaction. The pleasure and enjoyment of just being together.

That core feature includes, for example:

• A mutual sense of strong commitment to each other; and responsiveness to each other’s needs: “I know he/she has my back.”
• A mutual level of enjoyment with their sex life.
• A sense that their partner was happy with their relationship, and an infrequent, low level of conflict with each other.

All of those findings from the empirical study match what we see clinically, as well, among couples that develop long-term, sustained pleasure in their relationships. The study was published in PNAS, the Proceedings of the National Academy of Sciences.

How Couples Build It

What the research can’t show, of course, is how such couples “grow” that kind bond of connection, trust, and pleasure. Here, both empirical and clinical research point to some of what they do to create a positive dynamic.

Overall, the most encompassing is their commitment to ongoing openness and exposure to each other – mutually revealing their hopes, fears, desires, and sense of where they want to go — as two separate individuals joined together in this journey through life. I described here how couples do that through a practice of “Radical Transparency."

There is some corroborating evidence from empirical research. For example:

• A willingness to forgo personal interests and knowing when to put your partner's needs ahead of your own. Letting go of self-interest in this way is directly linked to a long-lasting, happy relationship. Staying entrenched in your own ego won't do it, as I wrote about here, and is reflected in research by John Gottman and others.
• Feeling appreciated and valued by your partner. That tends to strengthen your marriage or committed relationship, and it increases your belief about how enduring your relationship will be over time. This was found in a University of Georgia study that I wrote about here.   
• A different study I cited in this post, conducted at Wake Forest University, found that your relationship is strengthened when your stressed-out partner feels really understood and listened to. It occurs not just through words of support, but through multiple forms of conveying empathy — eye contact, listening, and generally conveying understanding and caring, nonverbally. The key is tuning in to what your partner perceives as helpful. Inquire about that if you’re not sure — and don’t assume that you know.

Of course, knowing the key to couples' happiness and enjoyment with each other over the long term is one thing, That's the science part. Really practicing it? That's the art of the relationship.