Twin Research


Intrinsic and extrinsic religiousness: genetic and environmental influences and personality correlates

Thomas J Bouchard Jra1 c1, Matt McGuea2, David Lykkena3 and Auke Tellegena4

a1 University of Minnesota, Minneapolis, USA.

a2 University of Minnesota, Minneapolis, USA.

a3 University of Minnesota, Minneapolis, USA.

a4 University of Minnesota, Minneapolis, USA.


This report presents findings for the Intrinsic (IR) and Extrinsic (ER) religiousness scales from the Minnesota Study of Twins Reared Apart. The scales were shown to be internally consistent, sufficiently distinct from the scales of the California Psychological Inventory and the Multidimensional Personality Questionnaire and unrelated to a number of measures of response style to justify treating them as distinct traits. The I scales also showed considerable evidence of construct validity in its correlations with religious fundamentalism and authoritarianism as assessed by the MMPI and Altemeyer's Right-Wing Authoritarianism scale. Data on IR and ER from 35 pairs of monozygotic twins reared apart (MZA) and 37 pairs of dizygotic twins reared apart (DZA) were fitted to a biometric model and demonstrated significant heritability (0.43 and 0.39), with a model containing genetic plus environmental factors fitting significantly better than a model containing only an environmental component. Twin similarity could not be explained by placement on a self-reported measure of family Moral Religious Emphasis as measured by the Family Environment Scale.

(Received April 29 1999)

(Accepted May 04 1999)


  • twins;
  • religiousness;
  • personality


c1 Correspondence: Thomas J Bouchard Jr, Department of Psychology, Elliott Hall, University of Minnesota, 75 East River Road, Minneapolis, Minnesota 55455, USA. Fax: 612 6262079;