Charting the Shift: Age as a Moderator of the Genetic and Environmental Influences on Reading

Reading is influenced by genes and environments throughout life. Using a U.S. twin sample (N = 1086; 564 Male: 522 Female; Age M = 7.46 years, SD = 1.57, with 90% self-reported as White, 8% Black, 1% Asian, 1% Alaskan, Native American, or Native Pacific Islander, and 11% self-reported as Hispanic), we used a Gene-by-Environment model with age as a moderator to examine how the balance of genetic and environmental influences on reading differed by age. Reading was measured with the DIBELS Next Composite from the beginning of academic year 2018/19. We observed small increasing genetic influences and larger decreasing shared environmental influences on reading from ages 5 to 7 that began to plateau around age 8. Non-shared environmental influences on reading were low and relatively stable from ages 6 through 12 following an uptick between ages 5 and 6. Our results are consistent with the bioecological framework, the emerging gene-environment-time model, and theories of reading development.