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ERIC Number: EJ1168778
Record Type: Journal
Publication Date: 2018-Jan
Pages: 15
Abstractor: As Provided
ISSN: ISSN-1092-4388
Longitudinal Study of Language and Speech of Twins at 4 and 6 Years: Twinning Effects Decrease, Zygosity Effects Disappear, and Heritability Increases
Rice, Mabel L.; Zubrick, Stephen R.; Taylor, Catherine L.; Hoffman, Lesa; Gayán, Javier
Journal of Speech, Language, and Hearing Research, v61 n1 p79-93 Jan 2018
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 0.44-0.92 at 6 years. The highest estimate, 0.92, 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.
American Speech-Language-Hearing Association. 2200 Research Blvd #250, Rockville, MD 20850. Tel: 301-296-5700; Fax: 301-296-8580; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Research
Education Level: N/A
Audience: N/A
Language: English
Sponsor: National Institutes of Health (DHHS)
Authoring Institution: N/A
Identifiers - Location: Australia
Identifiers - Assessments and Surveys: Peabody Picture Vocabulary Test; Columbia Mental Maturity Scale; Goldman Fristoe Test of Articulation
Grant or Contract Numbers: R01DC005226; R01DC001803; NIHP30DC005803; R42DC013749; P30HD002528