SILENCE IS LIBERATING - REMOVING THE HANDCUFFS ON GRAMMATICAL EXPRESSION IN THE MANUAL MODALITY

Grammatical properties are found in conventional sign languages of the deaf and in unconventional gesture systems created by deaf children l acking language models. However, they do not arise in spontaneous gest ures produced along with speech. The authors propose a model explainin g when the manual modality will assume grammatical properties and when it will not. The model argues that two grammatical features, segmenta tion and hierarchical combination, appear in all settings in which one human communicates symbolically with another. These properties are pr eferentially assumed by speech whenever words are spoken, constraining the manual modality to a global form. However, when the manual modali ty must carry the full burden of communication, it is freed from the g lobal form it assumes when integrated with speech-only to be constrain ed by the task of symbolic communication to take on the grammatical pr operties of segmentation and hierarchical combination.