Can a person’s moral decisions on dilemmas of foreseen harm be traced back to one single gene? That’s what a new paper in the open access journal PLoS ON suggests. The authors write that “a serotonin transporter (5-HTTLPR) genotype predicts responses to moral dilemmas featuring foreseen harm to an innocent.”

Here’s a breakdown from Scientific American blogger Christie Wilcox:

[The researchers] took 65 healthy volunteers and tested their genes to see what versions of the [serotonin] promoter they had. Overall, 22 had two copies of the long form of the gene (LL), 30 had one of each (SL), and 13 had two copies of the short form of the gene (SS). They then asked these individuals to rate the overall morality of a variety of scenarios, including ones like the one above where one person is unintentionally harmed to save five others.

The results were clear: although the three groups showed no differences when presented with morally neutral scenarios or those where harm is intentionally caused to an individual, there were significant differences between groups when it came to scenarios of foreseen harm. Those with the long form of the promoter were much more willing to approve of harming one person to protect five. They felt that doing so was the better moral choice:

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