Longitudinal Study of Language and Speech of Twins at 4 and 6 Years: Twinning Effects Decrease, Zygosity Effects Disappear, and Heritability Increases.
J Speech Lang Hear Res
; 61(1): 79-93, 2018 01 22.
Article
in En
| MEDLINE
| ID: mdl-29255901
ABSTRACT
Purpose:
This study investigates the heritability of language, speech, and nonverbal cognitive development of twins at 4 and 6 years of age. Possible confounding effects of twinning and zygosity, evident at 2 years, were investigated among other possible predictors of outcomes.Method:
The population-based twin sample included 627 twin pairs and 1 twin without a co-twin (197 monozygotic and 431 dizygotic), 610 boys and 645 girls, 1,255 children in total. Nine phenotypes from the same comprehensive direct behavioral assessment protocol were investigated at 4 and 6 years of age. Twinning effects were estimated for each phenotype at each age using general linear mixed models using maximum likelihood.Results:
Twinning effects decreased from 4 to 6 years; zygosity effects disappeared by 6 years. Heritability increased from 4 to 6 years across all 9 phenotypes, and the heritability estimates were higher than reported previously, in the range of .44-.92 at 6 years. The highest estimate, .92, was for the clinical grammar marker.Conclusions:
Across multiple dimensions of speech, language, and nonverbal cognition, heritability estimates are robust. A finiteness marker of grammar shows the highest inherited influences in this early period of children's language acquisition.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Speech
/
Twins, Dizygotic
/
Twins, Monozygotic
/
Child Language
Type of study:
Guideline
/
Observational_studies
/
Prognostic_studies
/
Risk_factors_studies
Limits:
Child
/
Child, preschool
/
Female
/
Humans
/
Male
Language:
En
Journal:
J Speech Lang Hear Res
Journal subject:
AUDIOLOGIA
/
PATOLOGIA DA FALA E LINGUAGEM
Year:
2018
Document type:
Article