Rule invention in the acquisition of morphology revisited: a case of transparent semantic mapping.

This paper presents a case study of a language-impaired child who signaled the distinction between English singular and plural using suprasegmental cues rather than the usual segmental form used within the parent language. Acoustic analyses performed within the first study in the paper revealed that the suprasegmental features used to maintain this distinction included various duration, fundamental frequency, and intensity parameters. Acoustic analyses were also performed on a set of matched two- and four-item plural forms within a second study. The results of these analyses indicated that the same acoustic parameters were used to distinguish two-item plural forms from four-item plural forms. This case of linguistic creativity is offered as further evidence in support of the model of language acquisition that emphasizes the active role children take in the acquisition process. Additionally, the phonological, morphological, and psycholinguistic factors that may contribute to such rule invention are discussed.