Selecting, developing and supporting key word sign vocabularies for children with developmental disabilities

There are many potential foci that warrant intervention and support in children with developmental disabilities (Beukelman & Mirenda, 2013). Arguably, one of the most fundamental is the development of language to enable a child to learn about and participate in their world. Of all the relevant domains, it is vocabulary development that receives considerable attention and input, particularly in the early years. Vocabulary is considered to be all the words existing within a given language which a person has the potential to learn and use. An individual vocabulary, or lexicon, is a set of words with which that individual is familiar. It is usually a subset of all available words and in response to developmental, environmental and experiential factors is dynamic, fluid and continues to grow over time (Hockema & Smith, 2009). Individual vocabularies can differ significantly in terms of: (a) total number of items, (b) distribution of items across word classes (e.g., nouns, verbs, adjectives, prepositions), (c) phonological, semantic, morphological and syntactic complexity (d) suitability in representing a range of semantic functions (e.g., agents, objects, actions) and pragmatic functions (e.g., greetings, requests, comments, directives), and (e) aptness to support both receptive and expressive use.