ERIC Number: EJ1040557
Record Type: Journal
Publication Date: 2014-Jun
Abstractor: As Provided
Reference Count: N/A
Late Language Emergence in 24-Month-Old Twins: Heritable and Increased Risk for Late Language Emergence in Twins
Rice, Mabel L.; Zubrick, Stephen R.; Taylor, Catherine L.; Gayán, Javier; Bontempo, Daniel E.
Journal of Speech, Language, and Hearing Research, v57 n3 p917-928 Jun 2014
Purpose: This study investigated the etiology of late language emergence (LLE) in 24-month-old twins, considering possible twinning, zygosity, gender, and heritability effects for vocabulary and grammar phenotypes. Method: A population-based sample of 473 twin pairs participated. Multilevel modeling estimated means and variances of vocabulary and grammar phenotypes, controlling for familiality. Heritability was estimated with DeFries-Fulker regression and variance components models to determine effects of heritability, shared environment, and nonshared environment. Results: Twins had lower average language scores than norms for single-born children, with lower average performance for monozygotic than dizygotic twins and for boys than girls, although gender and zygosity did not interact. Gender did not predict LLE. Significant heritability was detected for vocabulary (0.26) and grammar phenotypes (0.52 and 0.43 for boys and girls, respectively) in the full sample and in the sample selected for LLE (0.42 and 0.44). LLE and the appearance of Word Combinations were also significantly heritable (0.22-0.23). Conclusions: The findings revealed an increased likelihood of LLE in twin toddlers compared with single-born children that is modulated by zygosity and gender differences. Heritability estimates are consistent with previous research for vocabulary and add further suggestion of heritable differences in early grammar acquisition.
Descriptors: Twins, Toddlers, Genetics, Risk, Etiology, Developmental Delays, Language Acquisition, Vocabulary, Grammar, Hierarchical Linear Modeling, Regression (Statistics), Gender Differences
American Speech-Language-Hearing Association (ASHA). 10801 Rockville Pike, Rockville, MD 20852. Tel: 800-638-8255; Fax: 301-571-0457; e-mail: email@example.com; Web site: http://jslhr.asha.org
Publication Type: Journal Articles; Reports - Research
Education Level: N/A
Sponsor: National Institutes of Health (DHHS)
Authoring Institution: N/A
IES Grant or Contract Numbers: RO1DC05226|P30DC005803|P30HD002528