Covert Contrast in the Early Development of Speech Sounds in Children using Cochlear Implants

Covert contrasts represent intermediate productions that allow us broader insight into how children acquire a phonological system. However, little is known about the use of covert contrast in the development of speech sounds in children with cochlear implants (CIs). In particular, are these children using covert contrast in the same way that children with normal hearing (NH) do? Nine congenitally deafened children with CIs, ages 2;11 to 6;4 years (M = 4;9), who were implanted before age 3 were matched to typically developing children by articulation ability and gender. Their VCV productions from the OlimSpac were rated by 33 experienced listeners on an equal appearing interval scale to rate the phonetic accuracy of /t/ and its production as a substitution for /d/ and /ʧ/. Results indicated no differences in [t] production across groups. However, children with NH had a large, well-developed contrast between /t/ and /d/, but the later developing /tʃ/ showed little contrast with /t/. Children demonstrated the opposite trend. Their [t] for /d/ substitutions were more with CIs /t/-like, suggesting insufficient covert contrast for the voicing difference between these phones. However, they displayed a larger contrast for /t/ and /tʃ/ than the children with NH