Beauty and its neural reward are in the eye of the crowd

Let's be honest, most of us do it, at least some of the time. We modify our own opinions in line with what other people think, especially our friends and peers.

A problem for psychologists investigating the effect of peer influence is that it can be tricky to tell whether people are simply acquiescing in public, for show, or if their attitudes really have changed. A new study by a team of psychologists at Harvard University has used an innovative mix of behavioural and brain-scan methods to show that peer influence really can change how people value something, in this case the attractiveness of a face.

Fourteen male participants performed a series of 'hot-or-not' style ratings of pictures of 180 women's faces. For the majority of the faces, after they'd made their own rating, the students were shown the average rating given to that face by hundreds of previous participants. This was actually fixed by the researchers and was sometimes higher than the participant's own rating and sometimes lower.

About half an hour later, the participants rated the same faces again, but this time had their brains scanned whilst they did so. The revelation here was that the effect of the faces on reward-related regions in the participants' brains depended on the feedback the participants had received earlier about how their peers had rated those faces.

Let's focus on those faces that a participant had earlier given equal attractiveness ratings to, and which you'd therefore think they'd find equally rewarding to look at. In fact, among these faces, those that they'd been told earlier were rated as more attractive by previous participants, triggered more reward-related brain activity (the participants also increased the attractiveness ratings they gave to these faces). In contrast, the faces they'd earlier been told were rated as less attractive by peers, triggered less reward activity, and were now rated as less attractive by the participants.

A financial game played during the same scanning session allowed the reearchers to pin-point the brain areas involved in receiving monetary reward - the orbitofrontal cortex and nucleus accumbens. It was these same brain regions that were more active when the participants looked at female faces which they'd earlier been told were rated as more attractive by other men.

This isn't the first time that brain imaging has been used to show how social factors can alter the value we place on things. For example, a wine-tasting study tricked participants into drinking the same wine twice, once thinking it was an expensive bottle and another time thinking it was a cheap one. The participants' reward pathways were activated more when they thought the wine was expensive. In a similar fashion this new study suggests that the pleasure we find in looking at a face is dependent not just on what we think of it, but on what we think other people think of it.

'Rather than the result of individual weakness and faulty character, conformity appears to arise from the same neural systems that guide behaviour towards highly-valued outcomes, including such basic needs as food, water, and opportunities for reproduction,' wrote the team, led by Jamil Zaki. 'This emerging understanding of the neural basis of social influence suggests that members of our species are not only remarkable in their willingness to adopt the opinions and norms of others, but equally remarkable in their fundamental motivation for doing so.'

ResearchBlogging.orgJamil Zeki, Jason Mitchell, and Jessica Schirmer (2011). Social influence modulates the neural computation of valuePsychological Science, In Press.