Why Do Children Differ in Their Development of Reading and Related Skills?

Abstract

Modern behavior-genetic studies of twins in the United States, Australia, Scandinavia, and the United Kingdom show that genes account for most of the variance in children's reading ability by the end of the 1st year of formal reading instruction. Strong genetic influence continues across the grades, though the relevant genes vary for reading words and comprehending text, and some of the genetic influence comes through a gene–environment correlation. Strong genetic influences do not diminish the importance of the environment for reading development in the population and for helping struggling readers, but they question setting the same minimal performance criterion for all children.

ACKNOWLEDGMENTS

Funding was provided by the National Institutes of Health, grant numbers P50 HD027802 for the Colorado Learning Disabilities Research Center, and R01 HD038526 for the Colorado component of the International Longitudinal Twin Study (ILTS). The Australian component of the ILTS was supported by the Australian Research Council, A79906201, DP0663498, DP0770805. The Scandinavian component of the ILTS was supported by the Research Council of Norway 154715/330, the Swedish Research Council grants 345-2002-3701, PDOKJ028/2006:1, and 2011-1905, and the Swedish Council for Working Life and Social Research (2011-0177). We thank the twins and their families who participated in our research. The Australian Twin Registry is supported by an enabling grant from the National Health and Medical Research Council.