TY - JOUR
T1 - Longitudinal study of language and speech of twins at 4 and 6 years
T2 - Twinning effects decrease, zygosity effects disappear, and heritability increases
AU - Rice, Mabel L.
AU - Zubrick, Stephen R.
AU - Taylor, Catherine L.
AU - Hoffman, Lesa
AU - Gayán, Javier
PY - 2018/1/1
Y1 - 2018/1/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85040938892&partnerID=8YFLogxK
U2 - 10.1044/2017_JSLHR-L-16-0366
DO - 10.1044/2017_JSLHR-L-16-0366
M3 - Article
C2 - 29255901
AN - SCOPUS:85040938892
SN - 1092-4388
VL - 61
SP - 79
EP - 93
JO - Journal of Speech, Language, and Hearing Research
JF - Journal of Speech, Language, and Hearing Research
IS - 1
ER -