Cognitive modelling and the behaviour genetics of reading

While it is well known that reading is highly heritable, less has been understood about the bases of these genetic influences. In this paper, we review the research that we have been conducting in recent years to examine genetic and environmental influences on the particular reading processes specified in the dual-route cognitive model of reading. We argue that a detailed understanding of the role of genetic factors in reading acquisition requires the delineation and measurement of precise phenotypes, derived from well-articulated models of the reading process. We report evidence for independent genetic influences on the lexical and nonlexical reading processes represented in the dual-route model, based on studies of children with particular subtypes of dyslexia, and on univariate and multivariate genetic modelling of reading performance in the normally reading population. It is well established that the skill of reading has a strong genetic basis. Heritability data from behaviour genetic studies indicate that at least half of the variance in reading ability is genetic (DeFries, Fulker & LaBuda, 1987; Olson, Wise, Conners & Rack, 1989). These data suggest that an enhanced understanding of the nature of these genetic influences o