Discrimination of voicing on the basis of temporal envelope cues in 6-month old infants.

Abstract

Several studies indicate that profoundly deaf children receiving a cochlear implant (CI) under the age of 2 years are able to develop linguistic skills at a rate equal to similarly aged children with normal hearing. CI devices deliver temporal-envelope (E) cues in speech over a small number of frequency channels. This suggests that infants are able to use efficiently E speech cues at an early age. However, little work has been done to investigate the developmental time course of the ability to use E speech cues. A recent study suggests that normal-hearing children are able to use such cues at adult levels by the age of 5 years, but information is lacking for younger children. The present study assessed the ability of 6-month old infants with normal hearing to discriminate between voiced and unvoiced stop consonants (/aba/ versus /apa/) on the basis of E cues, using a head-turn preference procedure and speech tokens processed via a tone or a noise E vocoder. The spectral and temporal resolutions of vocoders were varied to determine whether or not the ability to use E speech cues is similarly constrained in infants and adults. Preliminary results indicate that this method is applicable to young infants.