The following started as a reply to a request for relationship advice (http://lesswrong.com/lw/zj/open_thread_june_2009/rxy) but is expected to be of enough general interest to justify a top-level post. Sometimes it is beneficial to have older men in the conversation, and this might be one of those times. (I am in my late 40s.)
I am pretty sure that most straight men strong in rationality are better off learning how the typical woman thinks than holding out for a long-term relationship with a women as strong in rationality as he is. If you hold out for a strong female rationalist, you drastically shrink the pool of women you have to choose from -- and people with a lot of experience with dating and relationships tend to consider that a bad move. A useful data point here is the fact (http://lesswrong.com/lw/fk/survey_results/cee) that 95%-97% of Less Wrongers are male. If on the other hand, women currently (*currently* -- not in some extrapolated future after you've sold your company and bought a big house in Woodside) find you extremely attractive or extremely desirable long-term-relationship material, well, then maybe you should hold out for a strong female rationalist if you are a strong male rationalist.
Here is some personal experience in support of the advice above to help you decide whether to follow the advice above.
My information is incomplete because I have never been in a long-term relationship with a really strong rationalist -- or even a scientist, programmer or engineer -- but I have been with a woman who has years of formal education in science (majored in anthropology, later took chem and bio for a nursing credential) and her knowledge of science did not contribute to the relationship in any way that I could tell. Moreover, that relationship was not any better than the one I am in now, with a woman with no college-level science classes at all.
The woman I have been with for the last 5 years is not particularly knowledgeable about science and is not particularly skilled in the art of rationality. Although she is curious about most areas of science, she tends to give up and to stop paying attention if a scientific explanation fails to satisfy her curiosity within 2 or 3 minutes. If there is a strong emotion driving her inquiry, though, she will focus longer. E.g., she sat still for at least 15 or 20 minutes on the evolutionary biology of zoonoses during the height of the public concern over swine flu about a month ago -- and was glad she did. (I know she was glad she did because she thanked me for the explanation, and it is not like her to make an insincere expression of gratitude out of, e.g., politeness.) (The strong emotion driving her inquiry was her fear of swine flu combined with her suspicion that perhaps the authorities were minimizing the severity of the situation to avoid panicking the public.)
Despite her having so much less knowledge of science and the art of rationality than I have, I consider my current relationship a resounding success: it is no exaggeration to say that I am more likely than not vastly better off than I would have been if I had chosen 5 years ago not to pursue this woman to hold out for someone more rational. She is rational enough to take care of herself and to be the most caring and the most helpful girlfriend I have ever had. (Moreover, nothing in my ordinary conversations and interactions with her draw my attention to her relative lack of scientific knowledge or her relative lack of advanced rationalist skills in a way that evokes any regret or sadness in me. Of course, if I had experienced a long-term relationship with a very strong female rationalist in the past, maybe I *would* experience episodes of regret or sadness towards the woman I am with now.)
Here are two more tips on mate selection for the straight men around here.
I have found that it is a very good sign if the woman either (1) assigns high social status to scientific ability or scientific achievement or finds scientific ability appealing in a man or (2) sees science as a positive force in the world. The woman I am with now clearly and decisively meets criterion (1) but does not meet criterion (2). Moreover, one of my most successful relationships was with a woman who finds science fiction very inspiring. (I do not BTW.) The salient thing about that was that she never revealed it to me, nor the fact that she definitely sees science as a positive force in the world. (I pieced those two facts together after we broke up.) The probable reason she never revealed them to me is that she thought they would clue me in to the fact that she found scientific ability appealing in a man, which in turn would have increased the probability that I would try to snow her by pretending to be better at science or more interested in science than I really was. (She'd probably been snowed that way by a man before she met me: male snowing of prospective female sexual partners is common.)
By posting on a topic of such direct consequence to normal straight adult male self-esteem, I am making myself more vulnerable than I would be if I were posting on, e.g., regulatory policy. Awareness of my vulnerability might cause someone to refrain from publicly contradicting what I just wrote. Do not refrain from publicly contradicting what I just wrote! The successful application of rationality and scientific knowledge to this domain has high expected global utility, and after considering the emotional and reputational risks to myself of having posted on this topic, I have concluded that I do not require any special consideration over and above what I would get if I had posted on regulatory policy.
And of course if you have advice to give about mate selection for the straight men around here, here is your chance.
(EDITED to avoid implying that all men are heterosexual.)