Personality similarity in twins reared apart and together.

Abstract

We administered the Multidimensional Personality Questionnaire (MPQ) to 217 monozygotic and 114 dizygotic reared-together adult twin pairs and 44 monozygotic and 27 dizygotic reared-apart adult twin pairs. A four-parameter biometric model (incorporating genetic, additive versus nonadditive, shared family-environment, and unshared environment components) and five reduced models were fitted through maximum-likelihood techniques to data obtained with the 11 primary MPQ scales and its 3 higher order scales. Solely environmental models did not fit any of the scales. Although the other reduced models, including the simple additive model, did fit many of the scales, only the full model provided a satisfactory fit for all scales. Heritabilities estimated by the full model ranged from .39 to .58. Consistent with previous reports, but contrary to widely held beliefs, the overall contribution of a common family-environment component was small and negligible for all but 2 of the 14 personality measures. Evidence of significant nonadditive genetic effects, possibly emergenic (epistatic) in nature, was obtained for 3 of the measures.Until recently, almost all knowledge regarding environmental and genetic causal influences on stable personality traits has come from studies of twins reared together. The findings have been both remarkable and puzzling. On the genetic side, regardless of the trait studied, the intraclass correlation for fraternal, or dizygotic (DZ), twins has approached .25; that for identical, or monozygotic (MZ), twins has approached .50 (Goldsmith, 1983;Nichols, 1978). Application of the simplest genetic model, the Falconer (1960) formula for heritability, [h 2 = 2(R M z -RDZ)], to those results yields a heritability of about .50. This leaves 50% of the variance to systematic environmental influences, measurement error, and temporal instability.Particularly puzzling, and contrary to what many psychologists would predict, is the finding that almost none of the enviThis research has been supported by grants from the University of Minnesota Graduate School, the Koch Charitable Foundation, the Spencer Foundation, the National Science Foundation (BNS-7926654), the Pioneer Fund, and the Harcourt Brace Jovanovich Publishing Company.We thank the following people for the time and effort they have given to testing the twins: Margaret Keyes, Jeff McHenry, Elizabeth Rengel, Susan Resnick, Joy Fisher, Jan Englander, and Ann Riggs. We are indebted to our colleagues and collaborators on the Minnesota Study of Twins Reared Apart project, Elke Eckert and Leonard Heston for their help and advice. We owe special thanks to our colleagues, Greg Carey and Matt McGue, for their valuable biometric advice and assistance. We also thank Jack Darley for his resolute and dedicated support and the Minneapolis War Memorial Blood Bank, Herbert Polesky, Director, for the blood testing.Correspondence concerning this article should be addressed to Auke Tellegen, Department of Psychology, Elliott Hall, University of Minnesota, 75 East River Road...

Felicidade: uma revisão

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A Five-Factor Theory Perspective

“…Funder, 1989). But the success of trait psychology in predicting real life outcomes (Barrick & Mount, 1991) and the convergence of personality scores across observers (Funder, Kolar, & Blackman, 1995) and separated twins (Tellegen et al, 1988) provide ample evidence that they do.…”

Steps to a neurochemistry of personality

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