The genetic and environmental etiologies of the relations between cognitive skills and components of reading ability

Abstract

Although previous research has shown cognitive skills to be important predictors of reading ability in children, the respective roles for genetic and environmental influences on these relations is an open question. The present study explored the genetic and environmental etiologies underlying the relations between selected executive functions and cognitive abilities (working memory, inhibition, processing speed, and naming speed) with 3 components of reading ability (word reading, reading comprehension, and listening comprehension). Twin pairs drawn from the Colorado Front Range (n = 676; 224 monozygotic pairs; 452 dizygotic pairs) between the ages of 8 and 16 (M = 11.11) were assessed on multiple measures of each cognitive and reading-related skill. Each cognitive and reading-related skill was modeled as a latent variable, and behavioral genetic analyses estimated the portions of phenotypic variance on each latent variable due to genetic, shared environmental, and nonshared environmental influences. The covariance between the cognitive skills and reading-related skills was driven primarily by genetic influences. The cognitive skills also shared large amounts of genetic variance, as did the reading-related skills. The common cognitive genetic variance was highly correlated with the common reading genetic variance, suggesting that genetic influences involved in general cognitive processing are also important for reading ability. Skill-specific genetic variance in working memory and processing speed also predicted components of reading ability. Taken together, the present study supports a genetic association between children's cognitive ability and reading ability.

Figure 1

Behavioral Genetic Hierarchical Model of the Cognitive Latent Variables. All numbers on single headed arrows are standardized regression coefficients and are significant (i.e, 95% confidence intervals do not include zero). If shaded, variance is significant (also per 95% confidence intervals). A = additive genetic variance; E = non-shared environmental variance. Residual variance (i.e., variance in the manifest variables not captured by the latent variable) = 1 – factor loading²

Figure 2

Behavioral Genetic Hierarchical Model of the Reading Ability Latent Variables. All numbers on single headed arrows are standardized regression coefficients and are significant (i.e, 95% confidence intervals do not include zero). If shaded, variance is significant (also per 95% confidence intervals). A = additive genetic variance; E = non-shared environmental variance. Residual variance (i.e., variance in a manifest variable not captured by the latent variable) = 1 – factor loading²

Figure 3

Behavioral Genetic Nested Model of the Cognitive Latent Variables. All numbers on single headed arrows are standardized regression coefficients and are significant (i.e, 95% confidence intervals do not include zero). If shaded, variance is significant (also per 95% confidence intervals). A = additive genetic variance; E = non-shared environmental variance. Note that total variance percentages may not equal 100% due to rounding. Residual variance (i.e., variance in the manifest variables not captured by the latent variable) = 1 – (factor loading for common latent variable² + factor loading for unique latent variable²)

Figure 4

Behavioral Genetic Nested Model of the Reading Ability Latent Variables. All numbers on single headed arrows are standardized regression coefficients and are significant (i.e, 95% confidence intervals do not include zero). If shaded, variance is significant (also per 95% confidence intervals). A = additive genetic variance; E = non-shared environmental variance. Residual variance (i.e., variance in the manifest variables not captured by the latent variable) = 1 – (factor loading for common latent variable² + factor loading for unique latent variable²)