Samuelsson, Stefan

Byrne, Brian John

Olsen, Richard K.

Hulslander, Jacqueline

Wadsworth, Sally

Corley, Robin

Willcutt, Erik G.

DeFries, John C.

2008

Genetic and environmental influences on early reading and spelling at the end of kindergarten and Grade 1 were compared across three twin samples tested in the United States, Australia and Scandinavia. Proportions of variance due to genetic influences on kindergarten reading were estimated at .84 in Australia, .68 in the U.S., and .33 in Scandinavia. The effects of shared environment on kindergarten reading were estimated at .09 in Australia, .25 in the U.S., and .52 in Scandinavia. A similar pattern of genetic and environmental influence was obtained for kindergarten spelling. One year later when twins in all three samples had received formal literacy instruction for at least one full school year, heritability was similarly high across country, with estimated genetic influences varying between .79 and .83 for reading and between .62 and .79 for spelling. These findings indicate that the pattern of genetic and environmental influences on early reading and spelling development varies according to educational context, with genetic influence increasing as a function of increasing intensity of early instruction. Longitudinal analyses revealed genetic continuity for both reading and spelling between kindergarten and Grade 1 across country. However, a new genetic factor comes into play accounting for independent variance in reading at Grade 1 in the U.S. and Scandinavia, suggesting a change in genetic influences on reading. Implications for response-to-instruction are discussed.

Learning and Individual Differences, v.18, p. 289-295

1873-3425

1041-6080

https://hdl.handle.net/1959.11/2978

Elsevier Ltd

Response to early literacy instruction in the United States, Australia, and Scandinavia: A behavioral-genetic analysis

Journal Article

Publication