The ‘incest taboo‘ is the aversion to being sexually attracted to our own family and evolutionary psychology has suggested it is an inherited adaptation to promote genetic diversity. A brilliant study just published in the journal Personality and Social Psychology Bulletin provides evidence that this is actually a cultural phenomenon, received wisdom if you like, because when awareness of the relationship is hidden, people find individuals who resemble their family more sexually attractive.
The debate about whether the incest taboo is an evolutionary adaptation or a cultural practice has quite a vintage as it became a point of contention between the followers of Edvard Westermarck, the Finnish anthropologist, and Sigmund Freud, the Austrian sex obsessive.
Westermarck believed the practice was an adaptation, based on the fact that it seems to occur universally, whereas Freud believed it was a cultural practice and that, actually, we all have incestuous desires that we typically repress – something now famous as the Oedipus complex.
More modern theories of incest avoidance have suggested that they rely on cognitive processes that judge how related someone might be based on our knowledge and our perception of similarity that may signify a genetic relationship.
However, the picture is a little muddied by the fact that recent psychology studies have shown that we are more likely to be attracted to people we are familiar with and that, to some extent, we are more attracted to people who are physically similar to us.
In an initial experiment, participants were asked to provide a photo of their parent to the researchers. During the study, they were asked to simply rate the attractiveness of strangers’ faces presented to them on a computer.
What they didn’t know was that just before they saw each face, half of the participants had the photo of their opposite-sex parent quickly flashed up on-screen – so quickly, in fact, that it was too fast to take in consciously. The other half, were given a subliminal image of someone else’s parent.
Those who were subliminally shown their opposite-sex parent rated the subsequent face as significantly more attractive, suggesting that their sexual interest had been slightly raised by subliminal exposure to their mother or father.
The researchers decided to go further by seeing how attraction would be affected if the person was exposed to images of themselves – after all, someone who shares 100% of their genetic material.
For this study this they used a technique called morphing to make images that had been digitally manipulated to be composites of two distinct faces – the person’s own and a stranger’s – to varying amounts. The participants were asked to rate the attractiveness of the faces, each of which ranged from being 0% their own face to a blend of 45% their face and 55% stranger.
The mix was never enough so the participants could tell that the faces were blended with their own, but they consistently rated faces that had more of themselves as more attractive.
A final experiment did exactly the same, but with an additional group who were told their own faces had been blended into the photos and that the study was investigating incest and attraction to faces that are designed to resemble genetic relatives.
The group who were aware what was happening showed exactly the opposite behaviour, they were less sexually attracted to faces that they more closely resembled.
In other words, the aversion to people we have a relation to may be based in conscious awareness, not an unconscious evolutionary adaptation.
This suggests is that Freud may have been right when he suggested that there may be an element of attraction to people in our own family.
The researchers doubt that we need to accept the full ‘Oedipus complex’ theory to make sense of this, but simply that the psychology of familiarity, bonding and attraction begins to develop in the family environment and so we retain an element of attraction to people we learnt about love with.
However, for sensible reasons, as a society we need to make sure we form new romantic relationships with people outside our immediate families, and so have instilled this knowledge in our culture.
Link to PubMed entry for study.