The resilience of combinatorial structure at the word level: morphology in self-styled gesture systems

Combinatorial structure at both word and sentence levels is widely recognized as an important feature of language--one that sets it apart from other forms of communication. The purpose of these studies is to determine whether deaf children who were not exposed to an accessible model of a conventional language would nevertheless incorporate word-level combinatorial structure into their self styled communication systems. In previous work, we demonstrated that, despite their lack of conventional linguistic input, deaf children in these circumstances developed spontaneous gesture systems that were structured at the level of the sentence, with regularities identifiable across gestures in a sentence, akin to syntactic structure. The present study was undertaken to determine whether these gesture systems were structured at a second level, the level of the word or gesture--that is, were there regularities within a gesture, akin to morphological structure? Further, if intra-gesture regularities were found, how wide was the range of variability in their expression? Finally, from where did these intra-gesture regularities come? Specifically, were they derived from the gestures the hearing mothers produced in their attempt to interact with their deaf children? We found that all of the deaf children produced gestures that could be characterized by paradigms of handshape and motion combinations that formed a comprehensive matrix for virtually all of the spontaneous gestures for each child. Moreover, the morphological systems that the children developed, although similar in many respects, were sufficiently different to suggest that the children had introduced relatively arbitrary distinctions into their systems. These differences could not be traced to the spontaneous gestures their hearing mothers produced, but seemed to be shaped by the early gestures that the children themselves created. These findings suggest that combinatorial structure at more than one level is so fundamental to human language that it can be reinvented by children who do not have access to a culturally shared linguistic system. Apparently, combinatorial structure of this sort is not maintained as a universal property of language solely by historical tradition, but also by its centrality to the structure and function of language.