Interaction of Knowledge Sources in Spoken Word Identification.

A gating technique was used in two studies of spoken word identification that investigated the relationship between the available acoustic-phonetic information in the speech signal and the context provided by meaningful and semantically anomalous sentences. The duration of intact spoken segments of target words and the location of these segments at the beginnings or endings of words in sentences were varied. The amount of signal duration required for word identification and the distribution of incorrect word responses were examined. Subjects were able to identify words in spoken sentences with only word-initial or only word-final acoustic-phonetic information. In meaningful sentences, less word-initial information was required to identify words than word-final information. Error analyses indicated that both acoustic-phonetic information and syntactic contextual knowledge interacted to generate the set of hypothesized word candidates used in identification. The results provide evidence that word identification is qualitatively different in meaningful sentences than in anomalous sentences or when words are presented in isolation: That is, word identification in sentences is an interactive process that makes use of several knowledge sources. In the presence of normal sentence context, the acoustic-phonetic information in the beginnings of words is particularly effective in facilitating rapid identification of words.