Published online by Cambridge University Press: 28 November 2008
Recent work has suggested that phrasing occurs in prelinguistic vocalizations, and that audition significantly influences prelinguistic vocal development. The present report is about the continuing study of a child who is referred to as congenitally acochlear because he was born with complete bilateral absence of cochleas. The only prior report on the vocal development of an acochlear child was provided in a previous article in this journal about the present subject (Lynch, Oiler, & Steffens, 1989). Because this child was not producing meaningful speech during the 27 to 42 months of age in which he was studied, investigation of him provided a unique opportunity to observe prelinguistic vocal development in the complete absence of auditory information. In the prior study of the acochlear child, the analytical focus was on developmental changes in relations between his syllable characteristics and those of mature speech. In the present study, the analytical focus was on a recently introduced approach to the study of prelinguistic vocalizations involving the description of syllable groupings within a prosodic hierarchy. Adult judges identified a hierarchy of syllables embedded within utterances and utterances embedded within prelinguistic phrases in the acochlear child's vocalizations. Similar to the prelinguistic phrases of typically developing infants and infants with Down syndrome previously reported on (Lynch, Oller, Steffens, & Buder, 1995), the present child's prelinguistic phrases were characterized by a systematic lengthening of phrase-final syllables and cohesive temporal patterning. In addition, the durations of the acochlear child's prelinguistic phrases were similar to those of typically developing infants. However, in contrast with those of typically developing infants and infants with Down syndrome, the durational features of the prelinguistic phrases of the acochlear child were relatively unstable across development. Overall, the results indicate that audition is not necessary for the formation of prelinguistic phrasing, but hearing does influence certain aspects of prelinguistic phrasing. Based on the data obtained on this subject, typically developing infants, and infants with Down syndrome, essential characteristics of well-formed prelinguistic phrases are proposed. These are termed “canonical” phrases; their production and development may be important in the acquisition of meaningful speech.