Do different academic skills and IQ share the same genetic factor?

Abstract

Research has shown that general intelligence and academic attainment are highly heritable. One important question that remains unresolved is to what extent the same genes influence IQ and different academic skills like reading and mathematics. A total of 202 pairs of Chinese twins (with 92 pairs identical, and 110 pairs non-identical) were recruited from Hong Kong. The participants were first to fourth grade Chinese-English bilingual readers. Four measures, Chinese word reading, English word reading, Mathematics, Raven’s Standard Progressive Matrices, were included in the present analyses. To adjust for age effects, the standardized residual scores regressing on age were used in the analyses. Results of univariate genetic analyses show that about one-third of the variance of Chinese word reading and mathematics were affected by genetic factors, while English word reading was more affected by common environmental factors. It was also found that the genetic correlation between Chinese and English reading was very high (.90), while that between reading and mathematics were moderate (.48 to .53). The environmental correlation between reading and mathematics was around .35, suggesting some shared home and school factors influencing general academic learning. We further tested two multivariate models to examine whether the three academic skills and IQ were affected by the same or different genetic factors. Results show that the best fitted model was having one common genetic factor. The present findings appear to support the generalist gene hypothesis for academic skills and general intelligence. Those who are born smarter tend to perform better academically in different school subjects. However, home and school education also plays some role on academic learning, especially on second language learning.