Genetic and environmental origins of verbal and performance components of cognitive delay in 2-year-olds

Citation
Tc. Eley et al., Genetic and environmental origins of verbal and performance components of cognitive delay in 2-year-olds, DEVEL PSYCH, 35(4), 1999, pp. 1122-1131
Citations number
36
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Psycology
Journal title
DEVELOPMENTAL PSYCHOLOGY
ISSN journal
0012-1649 → ACNP
Volume
35
Issue
4
Year of publication
1999
Pages
1122 - 1131
Database
ISI
SICI code
0012-1649(199907)35:4<1122:GAEOOV>2.0.ZU;2-W
Abstract
The authors investigated the etiology of several measures of cognitive dela y. Verbal (V) and performance (P) abilities were assessed in over 3,000 pai rs of 2-year-old twins. Group-differences heritability for general delay (t he lowest 5% of the V and P composite) was 35%. However, V and P delays con sidered independently showed large differences in group heritability (77% f or V vs. 40% for P). Specific delays with comorbid cases eliminated showed an even greater difference in group heritability (78% vs. 22%, respectively ). The small sample comorbid for both V and P delay also yielded high group heritability for bath V (77% ) and P (93%) scores. Shared environmental fa ctors also differed in magnitude for V (20%) and P (41%) delays. Because th e genetic and environmental origins of V and P delays in infancy differ, th ey are better considered separately rather than combined into a composite m easure of general cognitive delay.