Late language emergence means that a child's language is below age and gender expectations in the number of words they speak and combining two or more words into sentences. In this study 71 percent of two-year-old twins were not combining words compared to 17 percent of single-born children.
While previous behavioral genetics studies of toddlers have largely focused on vocabulary, the researchers introduced an innovative measure of early grammatical ability on the correct use of the past tense and the "to be" and "to do" verbs. The measure was inspired by the Rice/Wexler Test of Early Grammar Impairment, developed by Rice and Massachusetts Institute of Technology Professor Kenneth Wexler in 2001. It was the first test to detect the subtle but common language disorder, Specific Language Impairment.
Rice's collaborators in the international longitudinal project that began in 2002 are Professors Cate Taylor and Stephen Zubrick from the Telethon Kids Institute in Perth, Western Australia, and Professor Shelley Smith at the University of Nebraska Medical Center.
The study population is located in the vicinity of Perth, Western Australia, because it is demographically practically identical to Kansas City and several other U.S. Midwestern states. But in Australia health records are available and the Western Australia Twin Registry is a unique resource for researchers since it is a record of all multiple births, said Rice.
The research group has followed the development of 1000 sets of Western Australian twins from their first words. In 2012, the group was granted $2.8 million by the National Institute for Deafness and Other Communication Disorders for a fourth five-year-cycle that will enable researchers to continue to monitor the twins as they develop through adolescence. In addition to formal language test
|Contact: Karen Salisbury Henry|
University of Kansas