The rate of language delay among twins is almost twice as compared to the single-born children, reveals a recent study.
Distinguished Professor Mabel Rice from University of Kansas, who studied 473 sets of twins since their birth, revealed that compared to single-born children, 47 percent of 24-month-old identical twins had language delay compared to 31 percent of non-identical twins, and overall, twins had twice the rate of late language emergence of single-born children.
Rice said that the 'twinning effect', a lower level of language performance for twins than single-born children, was expected to be comparable for both kinds of twins, but was greater for identical twins, which strengthened the case for the heritability of language development.
He further added that all of the language traits analyzed in the study, namely vocabulary, combining words and grammar, were significantly heritable with genes accounting for about 43 percent of the overall twins' deficit.
Prematurity and birth complications were found to be more common in identical twins, and could also affect their higher rates of language delay, said Rice.
He concluded that the findings dispute the hypotheses that mothers whose attention was reduced due to the demands of caring for two toddlers, was a major attribute for delay in early language acquisition of twins, and this should reassure busy parents who worry about giving sufficient individual attention to each child.
The research is published in Journal of Speech, Language, and Hearing Research.