I'm curious about language acquisition among twins. I've heard it said that they often develop their own language (of sorts) and I was wondering if anyone has done any studies of this phenomenon.
The invented languages of twins, sometimes called 'twinspeak' are also known as cryptophasia or idioglossia. Peter Bakker of Aarhus University (Denmark) has published on this topic (abstract available here). According to Bakker twin languages are very common, occurring in about 40% of all twins, but soon disappear.
Regarding the structure of these languages, Bakker writes:
In all cases known, the language consists of onomatopoeic expressions, some invented words, but for the greatest part of words from the adult language adopted to the constrained phonological possibilities of young children. These words being hardly recognizable, the language may turn out to be completely unintelligible to speakers of the model languages, but they resemble each other in that they lack morphology and that word order is based on pragmatic principles such as saliency and the semantic scope of words. Neither the structure of the languages nor its emergence can be explained by other than situational factors.
The Bakker article seems to be hard to obtain. Further reading may be found in the bibliography of the subject Bernard Comrie posted to LinguistList in 1998.
