It's an old cliche, but generally speaking opposites don't attract: we actually tend to be attracted to people who look like us. The big exception is when we get stressed out, as mounting tension pushes us towards different-looking prospective mates.
In a result that seems to be making lots of murky but trenchant points about love, narcissism, stress, and self-loathing, researchers at Germany's University of Trier found that our stress levels actually change who we're attracted to:
Although humans usually prefer mates that resemble themselves, mating preferences can vary with context. Stress has been shown to alter mating preferences in animals, but the effects of stress on human mating preferences are unknown. Here, we investigated whether stress alters men's preference for self-resembling mates. Participants first underwent a cold-pressor test (stress induction) or a control procedure. Then, participants viewed either neutral pictures or pictures of erotic female nudes whose facial characteristics were computer-modified to resemble either the participant or another participant, or were not modified, while startle eyeblink responses were elicited by noise probes.
Before we go any further, I feel it should be pointed out that this is one of the most wondrously demented experiments I've ever heard of. If NASA's work involved more erotic photoshopping, maybe we'd still be headed to Mars. In any event, you can see an example of this image manipulation up top. Just what did the researchers find?
Erotic pictures were rated as being pleasant, and reduced startle magnitude compared with neutral pictures. In the control group, startle magnitude was smaller during foreground presentation of photographs of self-resembling female nudes compared with other-resembling female nudes and non-manipulated female nudes, indicating a higher approach motivation to self-resembling mates. In the stress group, startle magnitude was larger during foreground presentation of self-resembling female nudes compared with other-resembling female nudes and non-manipulated female nudes, indicating a higher approach motivation to dissimilar mates. Our findings show that stress affects human mating preferences: unstressed individuals showed the expected preference for similar mates, but stressed individuals seem to prefer dissimilar mates.
I'm not quite sure what to make of this. One possible interpretation is that stress levels correlate broadly with our self-esteem - the less stressed you are the more happy with yourself you are, and vice versa. Perhaps you're more likely to be attracted to those who remind you of yourself under those circumstances. Like I said, this study is trenchant, but murky. If ever there was a time when we still needed Sigmund Freud around, I feel like this is probably it.
Via NCBI ROFL. Top image modified from illustration in original paper.