Genetic and Environmental Influences on Personality: A Study of Twins Reared Together Using the Self- and Peer Report NEO-FFI Scales


  • Preliminary analyses of the data were presented at the seventh meeting of the International Society for the Study of Individual Differences, 66Warsaw. Poland, July 15–19, 1995. and in Angleitner, Riemann, Spinath, Hempel, Thiel, and Strelau (1995). This research was supported in part by funds from the Max-Planck Forschungspreis (awarded by the Alexander von Humboldt Stiftung and the Max-Planck Gesellschaft) to Alois Angleitner and Jan Strelau. We thank Peter Borkenau, Rainer Reisenzein. and Frank M. Spinath for helpful comments, and Wolfgang Thiel for his assistance in analyzing the data.

concerning this article should be addressed to Rainer Riemann, Department of Psychology, University of Bielefeld, Postfach 100131, 33501 Bielefeld, Germany. E-mail may be sent to


ABSTRACT Previous behavior-genetic research on personality has been almost exclusively based on self-report questionnaire measures. The purpose of this research was to measure personality constructs via self- and peer reports on the items of the NEO Five-Factor Inventory (Costa & McCrae, 1989). The sample included 660 monozygotic and 200 same sex and 104 opposite sex dizygotic twin pairs. We collected self- and two independent peer reports for each of the twins. Our analysis of self-report data replicates earlier findings of a substantial genetic influence on the Big Five (h2= .42 to .56). We also found this influence for peer reports. Our results validate findings based solely on self-reports. However, estimates of genetic contributions to phenotypic variance were substantially higher when based on peer reports (h2= .51 to .81) or self- and peer reports (h2= .66 to .79) because these data allowed us to separate error variance from variance due to nonshared environmental in-fluences. Correlations between self- and peer reports reflected the same genetic influences to a much higher extent than identical environmental effects.