AUG 22, 2019 8:20 AM PDT

Do You Inherit Your Morals?

WRITTEN BY: Annie Lennon

Morality is usually a subject discussed by philosophers, not biologists. But is it really a purely philosophical issues? After all, what makes us more susceptible to adopting certain moral codes? Research shows that this susceptibility may not be completely environmental as otherwise thought, and that there may be something of a genetic component too. 

Research has found that people taking serotonin reuptake inhibitors (SSRIs) tend to make different moral decisions to those not under the drug’s effects. When asked to make a snap decision on whether they would allow a group of five people to live or just one person to live, given that the death of one party would be inevitable, they were overall less willing to say that killing one person was more morally justified than killing the group of 5.

This research inspired an investigation into the role of serotonin reuptake (or absorption) in making moral decisions. Due to alterations in the promoter for one of the serotonin transmitter genes, there is a natural variation in serotonin reuptake ability among the general population. People with the long form of the promoter (L) have normal serotonin reuptake, whereas those with a shorter variant (S), have a lower serotonin reuptake, similar to those taking SSRIs (PLOS: 2011). 

Knowing this, the researchers conducted a study with 65 people carrying different variants of these genes: 22 with two copies of the L gene, 30 with a copy of both L and S, and 13 with two copies of the S gene. They then asked each person questions to understand their attitudes towards morality, and measured their response times.

For neutral moral decisions, or decisions involving the harm of one person, the researchers found little variation in moral judgement between each group. However, significant differences were seen when they were faced with scenarios of looking at inevitable harm to be inflicted on varying numbers of people, as in the example requiring prioritization of the fate of one person or five people (Wilcox: 2011). 

Matching earlier findings on moral decision-making of people taking SSRSs, those with the S variant of the serotonin promoter found little moral difference between harming a group of 5 people, or one person- either way it was wrong. On the other hand however, those with the L variant of the gene felt that harming one to protect five was the correct moral choice. When looking at response times however, the researchers noted that those with the LL variants tended to take longer than those with S variants, suggesting that they felt more moral conflict in making decisions, and that those with S variants felt less (Marsh: 2011). 

For the researchers, the findings go some way in demonstrating previously studied effects of holding the S variant gene; being more inclined towards negativity and a higher sensitivity to perceived threats from more reactivity in the amygdala (leading to a heightened emotional response). The research shows that the output of these factors tends to affect moral decision-making; in this case, the carrier of the S variant has an increased emotional responsiveness to the plight of the innocent victim, making him/ her reluctant to condone harm of an innocent person in any circumstance, even with the possibility of utilitarian gains (the survival of five) (ibid.). 

To conclude, it seems that genes responsible for the absorption of serotonin impact our moral decision-making process by impacting the way we interpret emotional events. With one gene variant making us more emotionally-charged in the decision-making process, it seems that genetic factors could go some way to explaining disagreements and conflict between people when making moral decisions that involve foreseen harm and utilitarian gains. 





Wilcox, Christie: Scientific American 

Marsh, Abigail A. et al.: PLOS 


About the Author
  • Science writer with keen interests in technology and behavioral biology. Her current focus is on the interplay between these fields to create meaningful interactions, applications and environments.
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