Why We Stopped Cooperating: What Game Theory Taught Me About Love, Loss, and Choosing Who You Want to Be

I have spent years trying to answer a question that has no clean answer:

How do two people fall in love, build a life, have children together — and still lose each other?

Not through one dramatic moment. Not because of a single betrayal. But slowly. Quietly. Through a thousand small choices that, over time, built a system neither person intended to create.

I recently started reading Game Theory: A Simple Introduction by K.H. Erickson, and something clicked. Game theory is the study of strategic decision-making — how people make choices when the outcome depends not just on what they decide, but on what others decide too. It is most often applied to economics, politics, and business.

But marriage? Marriage might be the most complex game any of us ever play.

Marriage Is Not a Moment. It Is a Repeated Game.

In game theory, a repeated game is one where the same players interact over and over again, across time. The choices made in round one shape round two. Round two shapes round three. And so on.

Marriage is exactly that. It is not a single decision made at an altar. It is thousands of decisions made across years — some enormous, most ordinary. How you respond when your partner is struggling. Whether you reach toward or pull away after conflict. Whether you choose to repair quickly or let things sit and quietly harden.

In repeated games, trust compounds. One act of generosity changes the next interaction. One act of repair changes the safety of the one after. Over time, the pattern matters far more than any single moment.

That is both the hope and the heartbreak of it.

When Cooperation Fails: The Prisoner's Dilemma at Home

Game theory describes a scenario called the Prisoner's Dilemma. Two players each face a choice: cooperate or defect. If both cooperate, both benefit. If one defects while the other cooperates, the defector gains and the cooperator loses. If both defect, both lose — but neither feels as exposed.

Here is what makes this so painfully relevant to marriage:

When trust is low, defection starts to feel rational.

"If I fully invest and they don't, I lose." "Why should I try if they aren't?" "I need proof before I soften."

So both people protect themselves. And ironically, that self-protection creates the very distance they were afraid of.

The marriage becomes transactional. Tit for tat. Every gesture calculated. Every act of kindness viewed with suspicion. The system starts rewarding defensiveness instead of connection — not because either person is bad, but because the structure of the game has shifted.

I watched this in my own marriage. Words like competition, rebellion, distrust — those were the textures of it. We were rarely in a state of cooperation and when we were, it didn't last because the foundation underneath it kept shifting. We weren't building toward something. We were managing against loss.

Game theory even has a name for the stable but losing outcome that emerges when two players both protect themselves indefinitely: the Nash Equilibrium. Both people locked in a pattern that is rational given what they expect from each other — and deeply unsatisfying for both.

That is not love failing. That is a system failing. And those are very different things.

The Information Problem Nobody Talks About

Here is something game theory surfaces that most relationship conversations miss: we never fully know each other's payoff structure.

No one fully knows another person's hidden fears, unspoken resentments, private narratives, or imagined futures. Early in love, we assume alignment — we want the same things. But over time, differences in incentives emerge. And often, people are not even fully conscious of their own.

One person may be driven by a deep need for security. Another by a need for freedom. One may prioritize feeling admired. Another, emotional safety. One may want closeness. Another may want, without ever saying it aloud, a way out.

When people stop feeling safe enough to reveal their real motives, the game shifts into hidden positioning. Affection becomes strategic. Silence becomes strategic. Even kindness can become a move.

And this is where things get truly painful: some of those hidden payoffs are not even real. They are imagined. Rooted in childhood wounds, betrayal trauma, old abandonment fears. Two people can be playing entirely different games while believing they are in the same marriage.

One may think: We are building a life together.

While the other is operating, unconsciously, from: I must never become powerless or unseen again.

That mismatch can erode a marriage even when love is genuinely present. Even when neither person intends harm.

When One Person Runs a Campaign

Here is where game theory gets uncomfortable — and important.

Erickson's book describes a dynamic in buyer-seller relationships where the seller's most powerful move is not to promote themselves directly. It is to convince the buyer that they are in pain without the product — that something is missing, that they cannot survive without it, that the seller is the only solution.

As long as the buyer believes that, the seller holds all the power. The outcome is locked in. And the buyer cooperates not from trust or genuine desire — but from manufactured fear.

Read that again through the lens of a marriage.

A dominant partner who needs control does not always say "I am in charge here." Instead, the campaign sounds more like:

"You wouldn't make it without me." "No one else would put up with you." "You should be grateful." "After everything I've done."

Over time, that campaign works. The other partner stops asking whether the relationship is good for them. They start asking how to survive it. They are no longer cooperating freely — they are cooperating from fear. And fear-based cooperation looks a lot like love from the outside, which is part of what makes it so hard to name and so hard to leave.

This is asymmetric information weaponized. One person knows the full picture — including that the fear is manufactured. The other only knows what they've been shown.

And here is the painful thread that connects it to everything else: you cannot choose who you want to be when someone has convinced you that you don't exist without them. The first act of courage, in those situations, is not fixing the relationship. It is recognizing the campaign for what it is.

Contempt Is Where Cooperation Collapses

Researcher John Gottman spent decades studying couples in his "Love Lab" at the University of Washington — observing more than 3,000 couples, tracking heart rates, facial expressions, and the specific words used during conflict. What he found was striking: four communication patterns predict divorce with over 90% accuracy. Criticism. Defensiveness. Stonewalling. And the most destructive of all — contempt.

Contempt is what happens when one partner stops believing the other is acting in good faith. It shows up as sarcasm, eye-rolling, mockery, moral superiority. And once contempt enters the room, game theory tells us exactly what happens: the entire strategic environment shifts.

Every action gets interpreted defensively. Acts of kindness are viewed with suspicion. The fundamental assumption — we are on the same side — collapses. And from that point forward, cooperation requires heroic effort because the system itself is working against it.

This is not a character flaw. It is a systems problem.

My Parents, My Marriage, and the Question I Kept Asking

My parents divorced when I was three and a half. They were young — early twenties — with two children and the grief of having lost a newborn. They both came from homes where marriages survived but did not necessarily thrive. They had never really been shown what sustained cooperation looks like from the inside.

So in a way, they were playing a game they had never been taught the rules to.

And then I grew up. And I got divorced. And looking back through this game theory lens, I can see it clearly now: we never built the cooperative infrastructure that a long marriage requires. We were in competition more than in collaboration. We retaliated more than we repaired. The tit-for-tat escalated rather than resolved.

I used to struggle to explain how that happens — how two people who loved each other could end up there. Now I understand it differently.

Love does not automatically override system dynamics.

Two people can genuinely love each other and still create a relational structure that continually punishes vulnerability and rewards defensiveness. The system can fail the love. And when that happens, it is not always visible until the damage has compounded across years of small choices.

"But People Don't Think That Way"

Some critics of game theory argue that it doesn't apply to real human relationships — that people are not strategic calculators, that love and habit and emotion drive our choices, not rational self-interest.

They're right that we're not calculators. But I think they're wrong that we don't think this way.

We do it all the time. We just call it something else.

Have you ever softened during an argument because you were thinking about the trip you're taking together next week? Have you chosen patience in a hard moment because you wanted to be the kind of person your kids see handling things well? Have you held your tongue not because you calculated the odds, but because you knew — ahead of time — that kindness was who you wanted to be?

That is backwards induction. That is game theory in the most human form imaginable.

The critics assume game theory means cold, selfish strategy. But the theory itself doesn't require that. It simply says: choices are shaped by the outcomes we anticipate. And those outcomes can be love, peace, a good vacation, a relationship worth having — not just individual gain.

The question is not whether we think ahead. We do. The question is: what future are we working backwards from?

The Question That Changes the Game

Game theory includes a concept called backwards induction. You start with the outcome you want — the end of the game — and work backwards to determine what choices, made today, lead there.

My mother taught me something I have carried with me for many years: Choose who you're going to be ahead of time. Don't wait until you walk into the room.

Not as a rigid script. Not as armor. But as a choice made from clarity rather than reaction. She didn't mean: don't let experience shape you. Life is supposed to shape us. What she meant was: don't let the heat of a moment take away your power to decide who you are. Go in knowing. Choose ahead of time.

I want to be kind. I want to be cooperative. I want to be forgiving. I want to be at peace.

Now work backwards. What do I have to choose today — in this conversation, in this conflict, in this moment of hurt — to be that person?

This is backwards induction as a life philosophy. And it changes the game entirely.

Many of us don't play our relationships reactively by accident — we choose to react rather than respond. Not always consciously. But when we haven't done the inner work of deciding ahead of time who we are, the moment decides for us. We hand our power over to whatever is loudest in the room — the hurt, the fear, the old wound. Because we haven't cultivated that centeredness intentionally, we default to reaction instead of returning to ourselves.

But what if we decided first?

Not naively. Not without discernment. But from a place of genuine intention:

I want to be someone who assumes goodwill. I want to be someone who repairs quickly. I want to be someone who brings warmth into hard conversations. I want to be someone who cooperates not because I'm guaranteed a return — but because that is who I choose to be.

That reframe shifts the question from "How do I protect myself?" to "Who do I want to be in this relationship?"

And it opens up a different kind of game — one where your choices are grounded in your own character, not just in calculated response to the other person's moves.

There is something powerful in that. Because even if the system around you is broken, even if the other person is not cooperating, even if trust has eroded — you still get to decide who you are. That is the one payoff no one can take from you.

The Best-Friend Marriage as Cooperative Game

Game theory tells us that in repeated games, sustained cooperation produces the greatest long-term return. And the marriages that do this well — the ones built on genuine friendship — tend to share a set of instincts that look very much like good game theory:

• They assume goodwill, even after conflict

• They repair quickly rather than let resentment compound

• They think long-term instead of optimizing for the moment

• They protect the relationship itself, not just their individual position

• They can tolerate temporary imbalance without panic, because they trust the long-term pattern

These couples are not perfect. They are not conflict-free. They are not perfectly matched.

But they have — consciously or not — chosen a cooperative orientation. And they return to it, again and again, even when it would be easier not to.

That is the real foundation of a lasting marriage. Not compatibility. Not chemistry. Not even love, on its own.

Repeated choices toward cooperation, honesty, repair, and friendship.

And underneath all of it: the decision — made ahead of time — about who you want to be.

A Few Questions to Sit With

Whether you are in a marriage, a long-term partnership, a friendship, or a team — these questions are worth slowing down for:

• What kind of game are you currently playing in your most important relationships — cooperative or competitive?

• When conflict rises, do you respond from who you want to be — or from who the moment pulls you to be?

• If you worked backwards from the relationship you want to have in ten years, what would you choose differently today?

• Is there a place where self-protection has become more costly than the vulnerability it was meant to prevent?

• Is there anywhere in your life where you might be cooperating from fear rather than from genuine choice?

• What does it mean to you to cooperate not for what you'll receive — but because of who you've decided to be?

Coach Kell is a trained coach and founder of The Human Coach. She works with people navigating transition, identity, and what comes next. Learn more at krhcoaching.com.

Further Reading & Sources:

• Game Theory: A Simple Introduction — K.H. Erickson

• Gottman, J. — Research on the Four Horsemen and marital stability (gottman.com)

• MIT News: Using Evolutionary Dynamics and Game Theory to Understand Personal Relations (2017)

A wedding, a marriage, and intention to make it last.