Discrimination of voicing (aba vs. apa)on the basis of Envelope temporal 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 E speech cues efficiently 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 noise vocoder. The spectral and temporal resolution of vocoders was varied to determine whether or not the ability to use E speech cues is similarly constrained in infants and adults.