"Rationality" -- or, really, just a thoughtful attitude -- has some major advantages in relationships, I've found. Some important relationship skills that require rationality:

• Being able to consider hypotheticals without bumping into ugh fields.

"If I ever cheated on you -- not that I would -- I would use a condom." You need a rational person to say this, and a rational person to hear it. An irrational person would never want to consider the possibility of cheating, and so wouldn't want to think of contingency plans; such a person might be offended by the very suggestion that a bad situation might happen. In the same vein, rational couples can discuss things like "if my business fails," "if we break up," "if this crazy feeling of limerence fades," and so on. You can't deal with bad contingencies well if you can't think about them or discuss them at all.

• Being able to suspend the Typical Mind Fallacy.

People are different. Something could matter a lot to your partner that doesn't matter at all to you. Or vice versa. You can make each other happier if you can put effort into the things that the other person is passionate about even when you can't imagine feeling that way yourself. This is also a great way to diffuse fights before they even start; before you assume your partner has a nasty thought or attitude, find out what he's actually thinking. It can be surprising.

• Learning from experience.

It's a rationalist skill just to be able to notice what your significant other does and predict that he'll keep doing it. So many relationship problems stem from the failure to notice patterns. Notice a behavioral pattern and you can learn to trust someone, learn his strengths and weaknesses, or learn to do what consistently makes him happier.

• Understanding that statistics predict but don't control our behavior.

Some stereotypes are roughly true in a statistical sense -- people like high status and attractiveness in their mates, for example. If you want to keep a relationship going well, you should try to do things that statistically make relationships go well. On the other hand, people are individuals, and if it's a good idea to modify yourself to be different from the statistical majority in some way, you can and should. Statistics are evidence, but not destiny.

• Curiosity.

Rationalists tend to have the attitude that the world is interesting. This means you will never be boring company. It also means you'll be willing to seek out new experiences with your partner.

• Not being a moron.

I never hear "judgment" among the top-ten qualities people desire in their partners, but I think it's more important than people realize. You really want to be with someone whose judgment you can trust and whose opinions you can respect. That doesn't mean "sober and boring," it means that you could trust your partner to be responsible for a choice that would affect your life profoundly (and that often happens in long-term relationships). Rationalists, if they're doing it right at all, have better judgment.