Prelinguistic Consonant Production and the Influence of Mouthing Before and After Cochlear Implantation

The goal of the study was to investigate prelinguistic consonant production and the influence of vocalizations that co-occurred with object mouthing on consonant production in infants with profound sensorineural hearing loss before and after cochlear implantation to advance knowledge of early speech development in infants with profound hearing loss.

Participants were 43 infants, 16 infants with profound sensorineural hearing loss and 27 hearing infants. In the mixed longitudinal and cross-sectional design, infants with profound hearing loss and age-matched hearing infants participated before cochlear implantation, at an average age of 9.9 mo, and/or after cochlear implantation, at an average age of 17.8 mo. Mean age at cochlear implantation for infants with profound hearing loss was 12.4 mo; mean duration of cochlear implant use at time of testing was 4.2 mo.

Before and after cochlear implantation, infants with profound hearing loss produced significantly fewer supraglottal consonants per consonant-vowel vocalization than hearing peers and had smaller overall consonant inventories. Before, but not after cochlear implantation, infants with profound hearing loss produced proportionally more vocalizations, supraglottal consonant-vowel vocalizations, and different supraglottal consonants in vocalizations during mouthing than did hearing infants.

The results document consonant production before cochlear implantation in a larger group of infants with profound hearing loss than previously examined. The results also extend evidence of early delays in consonant production to infants who received cochlear implants at 12 mo of age, and show that they likely miss the potential benefits of auditory-motor feedback in vocalization-mouthing combinations that occur before they have access to sound through cochlear implants.