The Heritability of Independent Reading, Shared Environmental Influences on Home Literacy, and Their Connections to Reading Ability

Purpose:
Reading ability is heritable. However, there is also a large literature suggesting that child-driven measures such as independent reading and caregiver-driven measures of the home literacy environment (HLE) are also important to literacy. The current study uses a longitudinal twin design to examine the etiology of these experiences as they relate to reading outcomes.
Method:
Same-sex twins from 436 families drawn from the Western Reserve Reading and Math Projects were assessed in multiple waves over six years, beginning in kindergarten or first grade. Participants were assessed on independent reading (the amount of time child spends reading alone, reading self efficacy, and willingness to take on difficult reading material), the home literacy environment (e.g. amount of time parents read to themselves, literacy materials in the home), as well as standardized measures of letter knowledge, word-level reading, and reading comprehension
Results:
Independent reading was highly heritable across all waves of assessment, and was associated with genetic influences related to reading. In contrast, the home literacy environment was mostly attributable to shared environment, and was associated with environmental factors, but only in early reading.
Conclusion:
The present study suggests that the probability of coming into contact with positive or negative environments, particularly when children gain control over their own reading, may be influenced by genetic influences associated with reading. One possibility is that the experience of independent reading may be more vulnerable to genetic risks for poor reading.