Hierarchical structure in a self-created communication system: Building nominal constituents in homesign.

Deaf children whose hearing losses are so severe that they cannot acquire spoken language and whose hearing parents have not exposed them to sign language nevertheless use gestures, called homesigns, to communicate. Homesigners have been shown to refer to entities by pointing at that entity (a demonstrative, that). They also use iconic gestures and category points that refer, not to a particular entity, but to its class (a noun, bird). We used longitudinal data from a homesigner called David to test the hypothesis that these different types of gestures are combined to form larger, multi-gesture nominal constituents (that bird). We verified this hypothesis by showing that David's multi-gesture combinations served the same semantic and syntactic functions as demonstrative gestures or noun gestures used on their own. In other words, the larger unit substituted for the smaller units and, in this way, functioned as a nominal constituent. Children are thus able to refer to entities using multi-gesture units that contain both nouns and demonstratives, even when they do not have a conventional language to provide a model for this type of hierarchical constituent structure.