I can guess how this sounds, but love relationships remind me of the Prisoner’s Dilemma.

Two conspirators are arrested and brought into separate interview rooms. They are both given the opportunity to turn state’s witness against the other. The one that takes the deal goes free, and the other gets ten years. If both confess, each gets six years. If they both refuse, they both get six months.

If I was in this situation, my answer would depend on the nature of the alliance I had developed with my partner in crime. In every relationship there are multiple opportunities in which we choose to either cooperate with the other or go our own way. Most of these occasions don’t have the consequence of being sentenced to prison for ten years, but you get the sense of a person’s loyalty if they pick up the check at the diner when you plan the crime, bring their own burglary tools, and take off in the getaway car before you get in. You also get an idea of the cost of betrayal when you scarf up the tip he left, bend his best lock pick, and arrive late because you couldn’t decide on a color for a ski mask.

Every one of these tests is a miniature prisoner’s dilemma and every one of these tests is found almost continuously in every kind of relationship. Temptations abound, no matter where you are, especially in love. Do you steal the blanket? Put the seat down for her? Do you give her the first piece of toast in the morning? Do the dishes? Get up to answer the phone even when you know it’s for her? When she tells you about that dress she’s going to buy do you really pay attention, or just nod and smile? When she’s not listening do you talk about her with respect? Do you flirt when she’s not looking? Are you adult enough to admit there’s adultery afoot?

We form alliances because we get a better reward when we both cooperate, but it’s inevitable that every alliance is going to be violated in some way. It is impossible to go along with every little thing your partner wants. How are these inevitable violations handled? When you tug the blanket, does she tug back? Does she go all ape shit when you pee on the seat? When you put the seat down for her, does she put it up for you? Does she put the flirting in perspective, forgive the adultery? If she does, does it make her a patsy? If she doesn’t, is she just being a bitch?

Scientists have studied the prisoner’s dilemma by having players adopt certain strategies to see which win most often. Some will always cooperate, no matter how strong the temptation. Those players end up exploited. Their partners have no reason to play along since there is no penalty for failing. Others never work together with their partners, they give in to temptation every time. No one ends up trusting them. They say the winning strategy is called Tit-for-Tat: cooperate every time until your partner fails to, then punish him by withholding cooperation at the next opportunity. This will teach him a thing or two.

There’s one problem with that, though. We believe we are much better at detecting when we lose our partner’s engagement than we really are. The next time you are having a conversation with someone, watch her and you will see there are moments that she does not appear to pay attention, a minor violation in the alliance that could really piss you off. The thing is, she might actually be paying attention, or she might be the kind that can pay attention to two things at once. Ask her what you just said and you might be surprised that she can repeat it word for word.

There are times, though, that she can’t. You lost her; she tuned out, spaced out, went blank. It happens. If you taped it, hit the rewind, and play it back, you might discover something. You were boring. You went on and on and were inattentive to non-verbal cues that she wanted to participate in the conversation. Or you made your point in such a way that she couldn’t follow. Each of these errors is a violation of the alliance. You broke faith before she did.

We have built in, exquisite instruments that detect betrayal so sensitively calibrated that we are always chasing false alarms. What’s more, the instrument does not work on the operator. You don’t know when you are doing it. There’s a moral to the story. When you believe that your partner is violating your alliance, look to see if maybe you did so first.