Twin study uncovers heritable roots of moral thinking

A study published in Personality & Individual Differences reports that our fundamental moral orientations may be significantly influenced by our genetics. Conducted by Timothy C. Bates, this research reveals that whether we lean toward utilitarian or Kantian ethical frameworks might be partially written in our DNA.

For centuries, moral philosophers have debated two competing ethical frameworks. Utilitarianism, championed by Jeremy Bentham, holds that the right action is whatever maximizes overall well-being. In contrast, Kantian ethics maintains that certain moral duties are absolute, regardless of consequences.

While these competing viewpoints were long thought to stem from psychological differences, the question remained: are these differences shaped primarily by our upbringing and environment, or do they have deeper biological roots?

To answer this question, Bates analyzed data from the Brisbane Adolescent Twin Study, examining 439 monozygotic (identical) twins, who share 100% of their genetic makeup, and 627 dizygotic (fraternal) twins, who share approximately 50% of their genes.

The participants, representative of the Australian population in terms of socioeconomic background and ethnicity, completed the Oxford Utilitarianism Scale (OUS), which measures two distinct dimensions of utilitarian thinking: Impartial Beneficence (the commitment to maximizing well-being impartially, without favoring any individual or group) and Instrumental Harm (the willingness to use coercion or harm to achieve a greater good).

Impartial Beneficence showed 58% heritability, while Instrumental Harm demonstrated 42% heritability. Overall utilitarian inclination had a heritability estimate of 52%. These two dimensions of utilitarian thinking were largely genetically independent. This means that someone genetically predisposed to care deeply about maximizing well-being for all isn’t necessarily inclined to support causing harm to achieve those goals.

The study found minimal evidence for shared environmental influences, suggesting that growing up in the same household had little impact on developing these moral perspectives. Instead, differences were primarily shaped by genetics and unique environmental experiences.

Bates acknowledges that the focus on Australian twins may limit the generalizability of these findings. Future studies could explore whether these genetic influences remain consistent across different cultural and socio-political contexts.

The study, “Genetic origins of Utilitarian versus Kantian moral philosophy in heritable motivations for egalitarian beneficence and coercive redistribution” was authored by Timothy C. Bates.