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New Study Finds First Links Between Genes and Moral Judgments

Brain Gene Image

Psychology professor Abigail Marsh and her team finds that people with a long allele of a particular gene rated unintentionally harming someone as more acceptable than did people with short allele carriers of the same gene.

October 5, 2011 – Psychology professor Abigail Marsh and her team of researchers today published the first evidence that a particular genotype can affect how people make life-or-death “utilitarian” moral judgments.

“Utilitarian moral judgments are those that save a bigger number of people even if it means an innocent person might be harmed in the process,” explains Marsh, the first author of the study published today in the online journal PLoS ONE.

Marsh and her team found that people with a long allele of a particular gene (a serotonin transporter) rated unintentionally harming someone as more acceptable than did people with short allele carriers of the same gene.

Study participants who carry the short allele version of the gene were reluctant to endorse actions resulting in foreseen harm to an innocent individual.

Abigail Marsh

Abigail Marsh

Emotional Responses

Marsh says this is the first time an association between a particular genotype and individual differences in moral judgments has been determined.

She collected the data while working at the National Institute of Mental Health and collaborated with colleagues from the National Institute on Alcohol Abuse and Alcoholism.

“What this study showed is that one variable that predicts how people’s moral judgments diverge when confronted with this kind of scenario is a gene,” says Marsh, who has worked on the study at Georgetown since 2008. “It’s a gene that controls how serotonin is transported in the brain, and it affects how people respond emotionally.”

She says people who have the short version of the gene tend to have stronger emotional responses to negative events.

Understanding Mechanisms

The researchers say that the way the shorter allele affects serotonin function in the brain makes people who carry this allele more emotionally reactive to aversive stimuli.

“This helps to extend our understanding of the mechanisms underlying moral judgments,” write the authors.

Marsh and her co-researchers asked more than 60 volunteers to judge a set of 30 scenarios and rate them on a scale of one to seven (one being the least acceptable, seven being the most acceptable).

Participants rated several scenarios, such as a choice to intentionally kill one person in order to save the lives of five other people or to let the five other people die. In another scenario, the person could save five people without harming anyone else or not save the people.

“I think this study is useful in helping to point out that maybe the way people arrive at their moral intuitions is just different for different people, in ways that are very deeply rooted,” Marsh says. “It helps to understand why maybe people can’t agree on what the right answer to certain moral problems is.”

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