Twin Research

Articles

Genetic Simplex Modeling of Eysenck's Dimensions of Personality in a Sample of Young Australian Twins

Nathan A. Gillespiea1 c1, David E. Evansa2, Margie. M. Wrighta3 and Nicholas G. Martina4

a1 Queensland Institute of Medical Research, Brisbane, Australia. nathanG@qimr.edu.au

a2 Queensland Institute of Medical Research, Brisbane, Australia.

a3 Queensland Institute of Medical Research, Brisbane, Australia.

a4 Queensland Institute of Medical Research, Brisbane, Australia.

Abstract

The relative stability and magnitude of genetic and environmental effects underlying major dimensions of adolescent personality across time were investigated. The Junior Eysenck Personality Questionnaire was administered to over 540 twin pairs at ages 12, 14 and 16 years. Their personality scores were analyzed using genetic simplex modeling which explicitly took into account the longitudinal nature of the data. With the exception of the dimension lie, multivariate model fitting results revealed that familial aggregation was entirely explained by additive genetic effects. Results from simplex model fitting suggest that large proportions of the additive genetic variance observed at ages 14 and 16 years could be explained by genetic effects present at the age of 12 years. There was also evidence for smaller but significant genetic innovations at 14 and 16 years of age for male and female neuroticism, at 14 years for male extraversion, at 14 and 16 years for female psychoticism, and at 14 years for male psychoticism.

(Received September 06 2004)

(Accepted September 22 2004)

Correspondence:

c1 Address for correspondence: Nathan Gillespie, Genetic Epidemiology Unit, Queensland Institute of Medical Research, Post Office Royal Brisbane Hospital, 300 Herston Road, Herston, Qld 4029, Australia.

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