Moral psychology
Does a serotonin gene variant shape moral attitudes and choices?
Open access · cc by · source: Europe PMC
People carrying two short copies of a serotonin transporter gene variant showed weaker implicit moral attitudes and were less willing to accept harming someone even when that harm was unavoidable.
Study at a glance
- Design
- Cross-sectional — Genotyped Han Chinese adults from cheek swabs and compared S/S, L/S and L/L groups on justice sensitivity, a moral IAT, moral dilemmas and state anxiety.
- N
- N=114 · 114 genotyped adults (L/L 13, L/S 39, S/S 62), drawn from a larger project that evaluated 567 adults.
- Population
- Right-handed Han Chinese adults from the general population in Taiwan, screened for major psychiatric illness.
- Outcome
- Implicit moral attitude (IAT D score), permissibility ratings for personal, impersonal and non-moral dilemmas, justice sensitivity, state anxiety.
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Key findings
Genotype groups did not differ in justice sensitivity, but implicit moral attitude scores were lower for people with two short copies than for those with two long copies, falling by about 0.117 per extra short copy. Short-short carriers were also less willing to endorse harm in personal dilemmas where the victim's harm was inevitable, with willingness dropping about 9.27% per short copy; genotype did not matter for the other dilemma types. State anxiety related to harm permissibility in opposite directions depending on the dilemma type.
Methodology
The researchers genotyped 114 adults for the 5-HTTLPR serotonin transporter polymorphism and grouped them as having two long, one of each, or two short versions. Participants completed a justice sensitivity questionnaire, an anxiety inventory, an Implicit Association Test pairing animated moral and immoral actions with positive and negative words, and a set of moral dilemmas including impersonal, personal-avoidable and personal-unavoidable harm.
Limitations
The long-long group was very small (13 people), which the authors flag as a reason for replication. Many outcomes were tested and several effects were marginal; the dilemma effect became non-significant in a multivariate test controlling for age and gender. Candidate-gene associations in small samples often fail to replicate, the sample is one ethnic group, and the design cannot show that the gene causes the moral differences rather than being linked through unmeasured factors.
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