Twin language or phonological disorder?

The acquisition of language in the preschool years by multiple-birth children is often reported to be atypical. Some researchers have claimed that they use 'twin language', i.e. an autonomous language specific to a multiple-birth set. This claim was investigated by describing and comparing the phonological characteristics of the speech of 19 sets of two- to four-year-old multiple-birth children, and by measuring multiple-birth children's understanding of their twins' or triplets' context-free speech. The results indicated that multiple-birth children are prone to phonological disorder and consequently their speech is often unintelligible. Siblings' phonologies evidenced some similarities, although they were not identical. Multiple-birth children were better able to understand their siblings' mispronunciations than were other children of the same age, although that understanding was dependent on how closely the error form resembled the adult form. While these three factors conspire to give the impression that 'twin language' is common, none of these findings provided support for the claim that multiple-birth children use an autonomous language.