Twin Research and Human Genetics

Articles

Multivariate Genetic Analysis of Academic Skills of the Queensland Core Skills Test and IQ Highlight the Importance of Genetic g

Mark A. Wainwrighta1 c1, Margaret J. Wrighta2, Michelle Lucianoa3, Gina M. Geffena4 and Nicholas G. Martina5

a1 Queensland Institute of Medical Research, Brisbane, Australia; Cognitive Psychophysiology Laboratory, School of Psychology, University of Queensland, Brisbane, Australia. Mark.Wainwright@qimr.edu.au

a2 Queensland Institute of Medical Research, Brisbane, Australia.

a3 Queensland Institute of Medical Research, Brisbane, Australia.

a4 Cognitive Psychophysiology Laboratory, School of Psychology, University of Queensland, Brisbane, Australia.

a5 Queensland Institute of Medical Research, Brisbane, Australia.

Abstract

This study examined the genetic and environmental relationships among 5 academic achievement skills of a standardized test of academic achievement, the Queensland Core Skills Test (QCST; Queensland Studies Authority, 2003a). QCST participants included 182 monozygotic pairs and 208 dizygotic pairs (mean 17 years ± 0.4 standard deviation). IQ data were included in the analysis to correct for ascertainment bias. A genetic general factor explained virtually all genetic variance in the component academic skills scores, and accounted for 32% to 73% of their phenotypic variances. It also explained 56% and 42% of variation in Verbal IQ and Performance IQ respectively, suggesting that this factor is genetic g. Modest specific genetic effects were evident for achievement in mathematical problem solving and written expression. A single common factor adequately explained common environmental effects, which were also modest, and possibly due to assortative mating. The results suggest that general academic ability, derived from genetic influences and to a lesser extent common environmental influences, is the primary source of variation in component skills of the QCST.

(Received August 29 2005)

(Accepted September 27 2005)

Correspondence:

c1 Address for correspondence: Mark A. Wainwright, Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Brisbane, QLD, 4029, Australia.

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