Mean Length of Utterance (MLU) in Children with Cochlear Implants

Purpose: To document the emergence of utterance length measured in both words and morphemes in children with severe and/or profound hearing loss who received cochlear implants by age 3. Method: A set of 49 conversational speech samples were evoked from 10 children (8 females, 2 males) with cochlear implants and transcribed and analyzed using SALT software. Raw MLU values measured in both words and morphemes were examined relative to both chronological age and post-implantation age (length of implant experience). MLU values were also compared to those of children with typical hearing by converting raw values to z-scores using data reported in Rice and colleagues (2010). Results: As with children with typical hearing, MLU values increased over time overall and for individual participants relative to both chronological age and post-implantation age. Z-score values were higher relative to post-implantation age than chronological age. Almost half of the MLU values were within 1.5 standard deviations of the mean for subjects with typical hearing when post-implantation age was used as the reference point. As the children gained experience with their implants, their Z-scores appeared to improve relative to children with typical hearing. Conclusions: MLU values in children with cochlear implants demonstrate delayed onset but appear to improve over time and may catch up with or approximate those of peers with typical hearing in many cases.