C.J. Clement

Babbling and the lack of auditory speech perception: a matter of coordination?

This paper concentrates on the question whether and where the lack of auditory perception can be traced in the early sound productions of deaf infants. A sensorimotor description system based on movements in the phonatory and articulatory speech production systems was developed to classify early infant vocalizations. Canonical babbling is a strong cue in the normal speech developmental process. Therefore the main question in this work was why deaf infants do not start to babble in their first year of life like normally hearing children do. Detailed analyses of early vocalizations of deaf and hearing infants revealed that auditory feedback is needed to lead to coordination of movements of the phonatory and the articulatory system, and that this coordination capacity is a prerequisite for the development of normal speech production.

Acoustical characteristics of sound production of deaf and normally hearing infants

Several recent studies have shown that speech production develops in an organized way, already in the first twelve months of life. This development is determined by several factors such as anatomical growth and physiological constraints. Studying the sound production of deaf infants and comparing this with that of normally hearing infants, can give more insight into the role of auditory speech perception on sound production. So far, no systematic work has been reported on the development of sound production of deaf infants in the first months of life. The present study is intended to address this topic in a systematic and controlled way. Preliminary results indicate differences in sound production between deaf and normally hearing infants, for instance with respect to utterance duration, even within the first half year of life. These findings strongly suggest that already in this early stage of speech development sound production is not solely determined by anatomical and physical constraints, but also by auditory perception and feedback. These results may contribute to a better understanding of the current models of early speech acquisition.