Acoustic investigations into the later acquisition of syllabic -es plurals

Purpose: Children acquire /-z/ syllabic plurals (e.g., buses) later than /-s, -z/ segmental plurals (e.g., cats, dogs). In this study, the authors explored whether increased syllable numberorsegmental factors best explains poorer performance with syllabic plurals. Method: An elicited imitation experiment was conducted with 14 two-year-olds involving 8 familiar disyllabic target plural nouns, half with syllabic plurals (e.g., bus → buses) and half with segmental plurals (e.g., letter → letters). Children saw pictures of the target items on a computer and repeated prerecorded 3-word-utterances with the target word in utterance-medial position (e.g., "The buses come") and utterance-final position (e.g., "Hear the buses"). Acoustic analysis determined the presence or absence of the plural morpheme and its duration. Results: Children had more trouble producing syllabic plurals compared with segmental plurals. Errors were especially evident in the utterance-medial position, where there was less time for the child to perceive/produce the word in the absence of phrase-final lengthening and where planning for the following word was still required. Conclusions: The results suggested that articulatory difficulties-rather than a word length effect-explain later acquisition of syllabic plurals relative to segmental plurals. These findings have implications for the nature of syllabic plural acquisition in children with hearing impairments and specific language impairment.