Do opposites attract? My girlfriend loves travelling and opera, and has political leanings to the right. I think that travelling is OK, but I hate opera and have always been politically to the left. We get on really well, but will these differences matter in the longer term?

It's only when you're dealing with magnetic poles that opposites attract. Relationship research would say it's conclusively proven that like attracts like. The term 'assortative mating' refers to the idea, there's a systematic pattern in how people choose partners (and they seem to pick people like them).

Most research has rated the characteristics of one partner against the other. It's found that couples usually share religious and political beliefs, and are about the same age. They're fairly similar in their education, intelligence and what they think matters in life. Most people go for someone as good-looking or plain as they are (though this rule excludes rich people, who are all gorgeous).

Part of the explanation for who we choose lies in who we meet. At work, your gym or at a friend's party, you'll meet people quite similar to you. You may, however, be familiar with the saying 'love is blind', suggesting you can fall for anyone, should you get the chance to meet them. But psychologists argue it's temporary: after three months, you can see again.

There's a strong drive to see similarities in someone you're attracted to, even when they don't exist. A small and not very scientific study at the University of Maine in the 80s asked 60 men to rank on a questionnaire how similar a woman was to them. Those who found her attractive were nearly twice as likely to find her remarkably similar.

If you differ in some areas, even religion, you may still have a great relationship. Why your differences might not matter may be down to your personalities. A study at Iowa University of 291 newlywed couples who had dated for three and a half years found that in a committed relationship, it was similarities in personality (such as how open or caring someone is) that kept couples happy and helped them negotiate, for example, what music they played in the car. Having the same values and attitudes wasn't quite enough.

However, there's no evidence that 'assortative mating' goes on around personality traits. Couples seem to hook up on the basis of quite obvious similarities and see if it works out afterwards. You, on the other hand, may have chosen more wisely.