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Are Moral Intuitions Heritable?

Abstract

Two prominent theoretical frameworks in moral psychology, Moral Foundations and Dual Process Theory, share a broad foundational assumption that individual differences in human morality are dispositional and in part due to genetic variation. The only published direct test of heritability, however, found little evidence of genetic influences on moral judgments using instrumentation approaches associated with Moral Foundations Theory. This raised questions about one of the core assumptions underpinning intuitionist theories of moral psychology. Here we examine the heritability of moral psychology using the moral dilemmas approach commonly used in Dual Process Theory research. Using such measures, we find consistent and significant evidence of heritability. These findings have important implications not only for understanding which measures do, or do not, tap into the genetically influenced aspects of moral decision-making, but in better establishing the utility and validity of different intuitionist theoretical frameworks and the source of why people differ in those frameworks.

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Data Availability

https://doi.org/10.7910/DVN/2NUL5A

Notes

  1. These findings have attracted substantial attention. We therefore provide a detailed reanalysis of the heritability of MFQ’s in the supplementary information accompanying this article (ESM §4). In these reanalyses we deliberately attempt to inflate the heritability of moral foundations by ignoring the proposed five-factor structure of the data, removing items for which DZ co-twin correlations are at least as large as the MZ co-twins (this ensures finding at least some heritability), and ignoring sex differences. After these heroic modifications to MFT and sidestepping standard methodical guidelines, we find at best genetic influences of .12 to .14 in the 10-item MFQ, and .23–.24 in the 20-item MFQ. Even then, tests in all cases find that models without genetic influences fit just as well as including them does.

  2. Kahane et al. (2015) also report that there is little relationship between DPT’s sacrificial hypothetical and other externally valid utilitarian beliefs.

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Acknowledgments

We thank Soad Hancock and Anjali Henders for project coordination, and David Smyth for database management. We thank John Hibbing, John Alford, and Nicholas Martin for their assistance in protocol development and data collection. Most of all, we thank the twins and their family members for participation in the study.

Funding

This work was supported by the US National Science Foundation (0729493,0721707).

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Correspondence to Peter K. Hatemi.

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Data collection and analysis was approved and conducted within the guidelines set forth by the Queensland Institute of Medical Research human research ethics committee and with the Helsinki Declaration of 1975, as revised in 2008.

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Informed consent was obtained from all participants before data collection.

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Analyses were conducted in the free package Mx and in SAS 9.4.

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Supplementary Information

ESM 1

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Smith, K., Hatemi, P.K. Are Moral Intuitions Heritable?. Hum Nat 31, 406–420 (2020). https://doi.org/10.1007/s12110-020-09380-7

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Keywords

  • Dual process theory
  • Genetics
  • Moral foundations theory
  • Moral intuitions