Jonna Kuntsi1 & Jim Stevenson2
In an attempt to integrate the genetic and cognitive/motivational literatures on hyperactivity, we tested different psychological theories of the disorder within a genetically informative design. Pairs of twins with at least one pervasively hyperactive member and control pairs were identified from general population samples in schools in Southern England. Ratings obtained from teachers and parents of 131 monozygotic and 136 dizygotic twin pairs confirmed previous reports of high heritability for hyperactivity (e.g. J. Stevenson, 1992, Behavior Genetics, 22, 337-344). To investigate which aspects of psychological functioning might be carrying this genetic effect, we assessed a subsample of 46 MZ and 47 DZ pairs on tests related to three theories of hyperactivity: the inhibition deficit, executive function/working memory and delay aversion theories. Comparisons between hyperactive and control children provided little support for the inhibition or executive function theories, whereas the data were consistent with a more motivational account of hyperactivity. There were genetic effects only on some of the measures, however. The strongest candidate for carrying the genetic effect on hyperactivity at the level of psychological functioning relates to the variability in their speed of responding.
Address: Behavioural Sciences Unit, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK, Tel: + 44-171-8310975, Fax: + 44-171-8317050, email:, J.Kuntsi@ich.ucl.ac.uk.
1Institute of Child Health, University College London Medical School, UK 2University of Southampton, UK