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

Abstract

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.

Figure 1

The black bars in both graphs display the number of multi-unit sentences containing nominal constituents that David would be expected to produce based on the multi-unit sentences he produced that did not contain nominal constituents (Expected). The gray bars display the number of multi-unit sentences containing nominal constituents that David actually produced (Observed) under the assumption: (1) that the nominal constituent functions as a single unit and contributes 1 unit to the sentence length count no matter how many gestures it contains (1a, top graph); and (2) that the nominal constituent contributes as many gestures as it contains to the sentence length count (1b, bottom graph). The Observed data fit the Expected values better in 1a. (X²=4.5, df = 6, ns) than 1b. (X²=55.6, df =6, p<.0001), suggesting that David's nominal constituents are functioning as a single unit in his sentences.

Figure 2

The proportion of gesture sentences in which the argument is conveyed by a single gesture (n=559, left bars) vs. sentences with the argument conveyed by a multi-gesture nominal constituent (n=35, right bars), categorized according to whether the sentences adhered to (black bars) or violated (gray bars) David's dominant word order.