A TWIN STUDY OF GENETIC INFLUENCES ON READING AND SPELLING ABILITY AND DISABILITY

TLDR

The study examined 285 pairs of 13‑year‑old twins using standardized intelligence, reading, and spelling tests, assessing genetic influence through MZ/DZ correlation and concordance analyses. Results indicated only moderate genetic effects on reading ability, whereas spelling showed substantial heritability (0.53, rising to 0.75 when controlling for intelligence) and strong genetic concordance for spelling disability.

Abstract

Abstract The reading skills of 285 pairs of 13‐year‐old twins drawn from the general population were studied. The twins were independently tested using standardized measures of intelligence, reading and spelling ability. The genetic contribution to reading ability was assessed by examination of correlations in monozygotk: (MZ) and student‐sex dizygotic (DZ) twins, and by analysing differences bi Mccen MZ and DZ twins in concordance of reading disability rates. The results suggested that, at this age, genetic factors play only a moderate role in general reading backwardness or specific reading retardation. However, when spelling ability was investigated, a heritability of 0.53 was obtained, increasing to 0.75 when intelligence was controlled. Strong genetic influences on spelling were also found when concordance rates for spelling disability were compared for MZ and DZ pairs.