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Genetics of Cognition: Outline of a Collaborative Twin Study

Published online by Cambridge University Press:  21 February 2012

Margie Wright*
Affiliation:
Genetic Epidemiology Laboratory, Queensland Institute of Medical Research, Brisbane, Australia. margieW@qimr.edu.au
Eco De Geus
Affiliation:
Department of Biological Psychology, Free University, Amsterdam, The Netherlands.
Juko Ando
Affiliation:
Faculty of Letters, Keio University, Tokyo, Japan.
Michelle Luciano
Affiliation:
Genetic Epidemiology Laboratory, Queensland Institute of Medical Research, Brisbane, Australia; Cognitive Psychophysiology Laboratory, School of Psychology and Department of Psychiatry, University of Queensland, Brisbane, Australia.
Danielle Posthuma
Affiliation:
Department of Biological Psychology, Free University, Amsterdam, The Netherlands.
Yutaka Ono
Affiliation:
Faculty of Letters, Keio University, Tokyo, Japan.
Narelle Hansell
Affiliation:
Genetic Epidemiology Laboratory, Queensland Institute of Medical Research, Brisbane, Australia; Cognitive Psychophysiology Laboratory, School of Psychology and Department of Psychiatry, University of Queensland, Brisbane, Australia.
Caroline Van Baal
Affiliation:
Department of Biological Psychology, Free University, Amsterdam, The Netherlands.
Kai Hiraishi
Affiliation:
Department of Life Sciences (Psychology), University of Tokyo, Tokyo, Japan.
Toshikazu Hasegawa
Affiliation:
Department of Life Sciences (Psychology), University of Tokyo, Tokyo, Japan.
Glen Smith
Affiliation:
School of Psychology, University of Queensland, Brisbane, Australia.
Gina Geffen
Affiliation:
Cognitive Psychophysiology Laboratory, School of Psychology and Department of Psychiatry, University of Queensland, Brisbane, Australia.
Laurie Geffen
Affiliation:
Cognitive Psychophysiology Laboratory, School of Psychology and Department of Psychiatry, University of Queensland, Brisbane, Australia.
Shigenobu Kanba
Affiliation:
Yamanashi Medical University, Tokyo, Japan.
Akira Miyake
Affiliation:
Department of Psychology, University of Colorado, Boulder, USA.
Nick Martin
Affiliation:
Genetic Epidemiology Laboratory, Queensland Institute of Medical Research, Brisbane, Australia.
Dorret Boomsma
Affiliation:
Department of Biological Psychology, Free University, Amsterdam, The Netherlands.
*
*Address for Correspondence: Margie Wright, Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Brisbane, QLD, 4029, Australia.

Abstract

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Amultidisciplinary collaborative study examining cognition in a large sample of twins is outlined. A common experimental protocol and design is used in The Netherlands, Australia and Japan to measure cognitive ability using traditional IQ measures (i.e., psychometric IQ), processing speed (e.g., reaction time [RT] and inspection time [IT]), and working memory (e.g., spatial span, delayed response [DR] performance). The main aim is to investigate the genetic covariation among these cognitive phenotypes in order to use the correlated biological markers in future linkage and association analyses to detect quantitativetrait loci (QTLs). We outline the study and methodology, and report results from our preliminary analyses that examines the heritability of processing speed and working memory indices, and their phenotypic correlation with IQ. Heritability of Full Scale IQ was 87% in the Netherlands, 83% in Australia, and 71% in Japan. Heritability estimates for processing speed and working memory indices ranged from 33–64%. Associations of IQ with RT and IT (−0.28 to −0.36) replicated previous findings with those of higher cognitive ability showing faster speed of processing. Similarly, significant correlations were indicated between IQ and the spatial span working memory task (storage [0.31], executive processing [0.37]) and the DR working memory task (0.25), with those of higher cognitive ability showing better memory performance. These analyses establish the heritability of the processing speed and working memory measures to be used in our collaborative twin study of cognition, and support the findings that individual differences in processing speed and working memory may underlie individual differences in psychometric IQ.

Type
Articles
Copyright
Copyright © Cambridge University Press 2001