The purpose of the two proposed experiments is threefold. First it is to determine if young hearing impaired children are capable of quickly incorporating unfamiliar words into their lexicons or vocabularies (fast mapping) in a fashion similar to normally hearing children. Secondly, the studies will evaluate the contribution of pre-existing lexical delays on the lexical acquisition skills of hearing impaired children. The third purpose is to assess whether hearing impaired children with normal lexicons use facilitory cues, such as lip movement and syllable number cues, in a more productive fashion than do hearing impaired children with delayed lexical skills. Forty-eight preschool children will serve as subjects, 24 of whom will have moderate to severe bilateral hearing losses. Twelve of the hearing impaired subjects will have delayed lexical skills, while the other 12 will have age appropriate skills. All of the hearing impaired children will use oral speech as their primary mode of communication. Two normally hearing control groups also will be included. One group of 12 will have normal lexical skills while the other group will have delayed lexical skills. The experimental protocol will consist of the subjects being exposed to a series of nonsense words associated with nonsense visual representations in a computer displayed and controlled game-like format. Half of the words will have a consonant-vowel-consonant (CVC) syllable structure while the other half will have a CVCV structure. After exposure and a 20 minute delay, the children will then be administered a series of tasks developed by Dollaghan (1985) to assess the extent of fast mapping. The tasks evaluate comprehension, production, recognition and prepositional knowledge, and will be administered via computer. The responses also will be recorded digitally. Two weeks after the first administration, the same children will complete a similar set of tasks except half of the word presentations will be synchronized with the lip movements of an animated speaker. The speaker's face will be displayed with the presentation of the remaining words but there will be no lip movements associated with the acoustic productions.
