Cracking the Code: What’s the Key to a Long-Lasting Relationship?

A stylized computer terminal screen showing the message “cracking the code” with a small heart

Relationship science isn’t easy. In forming any close bond — whether a friendship or romantic partnership — each party brings their strengths and weaknesses, their faults and foibles, and their unique needs and desires to the table. Fitting the puzzle pieces together is often harder than it looks (just ask Marriage Pact’s Relationship Science team).

Luckily, almost every relationship can be distilled down to two key components. The first, of course, is attraction. It’s hard to date or befriend someone without any affinity or admiration for them. But the second aspect — and arguably more important one — is longevity. You can like someone as much as you want, but if you aren’t compatible in the long run, it’s a matter of time before rifts start to form.

Sounds simple enough. But how do each of these factors play out in real life?

To learn more, I spoke to two relationship experts about the recipe for a long-lasting relationship. I first met with Dr. Douglas Rait, a Clinical Professor of Psychiatry and Behavioral Sciences at Stanford University who specializes in couples and family therapy.

Dr. Rait notes that proximity and propinquity are two of the most essential components when it comes to attraction. What does this mean? Essentially, the person you’re seeking a relationship with needs to be close to you, and you need to encounter them fairly frequently. This one might seem obvious, but continuous exposure to someone is important in order to develop a liking for them (and vice versa).

But nearnness doesn’t facilitate attraction on its own. Now that you’re in close proximity with another person, what draws you further towards them?

We’ll start with the age old question: does physical attractiveness really matter? The answer: kind of.

Dr. Rait: It seems kind of uncool at this point to say, “Yeah, it matters.” But it’s kind of part of the handshake. You need to feel that this is somebody you could have a potential connection with and that you’re drawn to in some way.

But it does obviously vary greatly between people, based on their preferences and their personal characteristics. It depends a lot on the degree to which people feel open to learning about another person and seeing what’s possible.

Ömercan Erol, a Relationship Psychologist on Marriage Pact’s Questionnaire Team, suggests that similarity in the way of attractiveness is a more important factor.

Ömercan: The research says that people aren’t necessarily attracted to things that are considered “universally attractive.” People are attracted to people who are similar to themselves, so they are drawn to people with similar levels of attractiveness.

As it turns out, similarity plays a crucial role when it comes to the deeper stuff, too. “People are drawn to those who are in some way like them,” Dr. Rait explains. Whether it be a unique personality trait, niche hobby, or life philosophy, some sort of common ground is essential for establishing a relationship.

Ömercan notes, however, that similarity in values plays a bigger role than similarity in personality.

Ömercan: When we meet someone, values are more easily communicated than personalities. For example, you might find a person who is punctual to be very attractive. But in order to be attracted to that trait, you need to observe it in a pattern. You’d want to see the behavioral manifestation of that person being punctual over time.

But values can be communicated right away. For example: “I can’t stand when people are late.” That’s more of a value statement, and the other person can easily determine whether they share that value. Values are more readily absorbed because they’re spoken through words. This allows you to evaluate a person more easily, which can facilitate attraction.

This doesn’t mean, of course, that we should only develop relationships with those identical to us. Complementarity plays an important role in long term compatibility, which we’ll explore shortly. But slight differences in personality can also foster attraction by providing “opportunities for learning and balance,” according to Dr. Rait. Ömercan expands upon this idea.

Ömercan: Complementarity is a tricky territory. We don’t have an exact answer for when differences in relationships are actually beneficial or not. But there’s a theory called self-expansion theory, which basically says that people develop relationships with those who expand the self. Meeting people who are different from you might help you improve and enhance yourself and gain new perspectives.

It’s important to note that attraction is not a guarantee that a relationship will be healthy. Ömercan describes a concept known as trauma coupling — which describes why people might be drawn to destructive or dangerous relationships.

Ömercan: People may find themselves stuck in patterns in their relationships — not because those are healthy relationships for them, but because those patterns are familiar to them. For example, if you’re abused as a kid, you could unknowingly seek others that are going to abuse you, and actually be attracted to those people because of the complementarity they might offer. Just because it’s familiar doesn’t mean it’s good for you.

Attraction might also depend on our own beliefs about ourselves and about the world. Those who validate our worldviews are more comforting than those who don’t, even if our beliefs are toxic or self-negative.

Ömercan: For those with an anxious attachment style, it’s actually a trend for them to seek out those with avoidant attachment styles, because they validate what they think about themselves. If you have an anxious attachment, you might think, “Men never respond to my texts, they’re never available, I must be unworthy.” And if you have those beliefs and those views of yourself, you’re actually more likely to seek out people who validate the way you see the world. It’s a kind of a confirmation bias.

Now that we’ve explored attraction, how do these concepts play out in the long-run?

We’ll start with physical attractiveness, which understandably matters less once you get past the initial stages.

Dr. Rait: If you look at dating apps, they started out almost entirely focused on physical appearance. Now there are many more questions that help people try to gauge whether they’re a fit in terms of values, or their basic attitudes towards how they walk through the world. Those are the features that end up having a lot to do with potential longevity.

Aside from shared values, there are some universal qualities that enable relationships to thrive long-term. Ömercan notes a distinction between two different kinds of traits: horizontal and vertical.

Horizontal traits are those which aren’t necessarily positive or negative: extraversion, spontaneity, ambition. In these cases, it depends on what each person desires in a partner and which values they hope to share in the long run. Vertical traits, on the other hand, are important to have in a relationship regardless.

Ömercan: Is there an objective good in a trait? If there is, it’s a vertical trait. Being kind is better than being not kind, for example, because that’s something we are generally attracted to.

When it comes to traits like flexibility and being generally easy-going, it’s best if both people possess the trait. However, it’s better to match someone easy-going with an inflexible person than it is to match two inflexible people together. Flexibility is just a good trait to have in a relationship in general, because it helps you adapt to change and conflict. There are some traits that depend less on similarity in the long run, because everyone should be striving for those traits in order to have a good relationship.

Dr. Rait describes some other key aspects of relationships that can predict longevity.

Dr. Rait: If you look at the research, there are a couple of elements that seem to recur. One is the affective climate in the relationship: closeness, warmth, connection. Establishing a positive emotional atmosphere where people feel that there’s trust, emotional safety, where they can truly be themselves.

Another is how people deal with conflict. There’s a difference between the couples that turn towards each other instead of away from each other, and the degree to which people allow their partner to influence them. Letting things go and having a forgiving attitude towards differences and conflict also matters. A sense of being on the same team is really important.

Complementarity also matters in the long term. Similarities on every front can be exhausting and frustrating; two partners who both struggle with planning and taking initiative might not be a good match, for example. When it comes to sexual compatiblity, two people who are both seeking dominance from their partner may quickly be disappointed. And like Ömercan described, it’s often a good thing if one partner possesses a trait like flexibility — especially if the other partner does not.

Nonetheless, there are some differences in relationships that might lead to conflict later down the line.

Dr. Rait: In some cases, two people may be drawn to each other for the same reason that they are eventually repelled by the other. You can imagine a person who is vibrant and has a lot of vitality, who is initially drawn to someone dependable and reliable, because they offer a nice balance.

But over time, the vibrant ones, the ones seeking novelty, might find a dependable person a little unexciting, whereas the dependable ones may become exasperated and not have their needs met either. The things that bring two people together may carry the seeds of what will eventually lead to a gap or a rupture in the relationship.

To sum things up, Ömercan offers a helpful overarching model for understanding the way relationships form and last. He touches on curiosity as an important aspect of a relationship — in other words, valuing the complexity and depth of the person you plan to share your life with.

Ömercan: One of the primary motivations when forming a relationship is to validate your understanding of the world and align on similar values and life goals. It’s a prerequisite — you have to be aligned on something in order to have that initial attraction.

Later, finding a bit of difference is natural and healthy, and helps you stay curious about the other person in the relationship. Curiosity is a very important part of a long-term relationship. If you’re 100 percent similar, it might be hard to invoke that.

But even if you have that initial attraction — maybe because you’re anxiously attached and you subconsciously want an avoidant person, or you don’t take good care of yourself and are drawn to someone super nurturing — that doesn’t mean it’s healthy. And that’s because those are differences that lead to problems later on.

There you have it, folks. While this may not make the search for love any less complicated, we hope it sheds some light on what you should be looking for.