There are great plays and bad ones, but the playwright’s actual text is only one aspect of a production. The very same words can take on radically different meanings depending on the whims of the director, the abilities of the actors and the setting of the stage. The same is true of our genes and our environments. In cases where genes affect our behaviour, the same stretch of DNA can lead to very different deeds, depending on individual circumstances. Just as a production defines a play, environments and cultures alter the effects of certain genes.

Heejung Kim from the University of California has discovered a great example of this effect by studying a gene called OXTR (or the ‘oxytocin receptor’, in full). The gene creates a docking station for a hormone called oxytocin, which is involved in all sorts of emotions and social behaviours, from trust to sexual arousal to empathy.

Kim looked at a specific version of the OXTR gene, whose carriers are allegedly more social and sensitive. But this link between gene and behaviour depends on culture; it exists among American people, who tend to look for support in troubled times, but not in Korean cultures, where such support is less socially acceptable. Culture sets the stage on which the OXTR gene expresses itself.

OXTR varies from person to person, and the DNA ‘letters’ at particular spots can affect the way we behave. According to previous studies, people with a ‘G’ at one specific site tend to be more sensitive parents, more empathetic and less lonely than those with an ‘A’. But most of these studies have been done with white, Western people who are hardly representative of the world at large – in fact, they’re positively W.E.I.R.D.

To looked outside this “thin and rather unusual slice of humanity”, Kim compared 134 Korean students with 140 American ones, all with comparable splits of age, gender and background. Using a questionnaire, she measured how stressed each volunteer was feeling at that point in their lives, and how they cope with stress. As with previous studies, Kim found that Koreans are less likely than Americans to turn to their social circle for support and they get less out of doing so; they are more concerned about burdening their friends and straining their relationships.

The OXTR gene exerts its influence against the background of these contrasting cultural conventions. Distressed Americans with one or more copies of the G version were more likely to seek emotional support from their friends, compared to those with two copies of the A version. But for the Koreans, the opposite was true – G carriers were less likely to look for support among their peers in times of need (although this particular trend was not statistically significant). In both cases, the G carriers were more sensitive to the social conventions of their own cultures. But the differences between these conventions led to different behaviour.

And in a further example of the influence of the environment, Kim only found this pattern among people who were experiencing a lot of stress. In the low stress group, she found that Americans were indeed more likely to seek emotional support than Koreans, but their OXTR gene had no bearing on their choices.

Of course, Koreans and Americans differ not just in their cultures, but in their genes (including many others beyond OXTR). To account for that, Kim also worked with a small group of 32 Korean-Americans who were born and raised in the US, but were genetically Korean. Kim found that the link between OXTR and emotional support among these volunteers was much closer to the culturally similar Americans than the genetically similar Koreans.

Richard Ebstein, who has worked on OXTR before, says, “Overall, I would say it’s a very interesting finding… These types of studies are needed to help us get a better understanding of how it’s not just nature or nurture but rather the interplay between the two that contributes to how we deal with the social environment.” However, he’s not convinced (and nor am I) that Kim looked at enough people, particularly in the extra experiment with the Korean-Americans. Ebstein wants to see them repeat the results in a much larger group.

Even so, Kim’s results are compelling. They’re also unusual in looking for an interaction between genes and culture. Many studies have looked at how nature and nurture work together but in most cases, the “nurture” bit involves something social that’s either harsh or kind, such as loving or abusive parenting. In one of the most famous examples, people with the ‘low-activity’ version of the MAOA gene tend to be more aggressive than those with the ‘high-activity’ one, but only if they’ve been abused or neglected as children. Kim’s study stands out because it looks as cultural conventions instead, and Ebstein says that it “provides an interesting new avenue for researching gene-environment interactions.”

Kim also hopes that her work will encourage more scientists to investigate the ways in which genes and culture evolve together. She notes that the G version of OXTR is more common among white Americans than Korea. It’s tantalisingly possible that American culture has come to emphasise social support partly because more people have genes that skew them towards social behaviour. So genes constrain culture, while culture creates the stage on which genes exact their influence.

Reference: PNAS http://dx.doi.org/10.1073/pnas.1010830107

More on genes and environment:

• Good teachers help students to realise their genetic potential at reading
• The MAOA guide to misusing genetics
• Ask an IVF baby: does smoking while pregnant lead to antisocial behaviour?
• Saucy study reveals a gene that affects aggression after provocation
• Making sense of obesity genes

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