Individual differences across caregivers in acoustic implementation of infant-directed and adult-directed speech: Modeling impacts on intelligibility in children with cochlear implants

Caregivers modify their speaking style from adult-directed speech (ADS) to infant-directed speech (IDS) when talking to infants. However, it is unclear how individual caregivers acoustically implement differences between ADS and IDS, and how these differences may affect experienced speech intelligibility by infants, particularly those with cochlear implants (CIs). Seven female talkers spoke fifteen utterances both in IDS and ADS. We analyzed these utterances and their cochlear implant-simulated versions (using 22-channel noise vocoders) to investigate how acoustic distances between ADS and IDS varied across talkers (based on Mel-frequency cepstral coefficients, MFCCs) and how the effect of these shifts in speaking style on utterance intelligibility were different between talkers (using the acoustic index of speech-to-reverberation modulation energy ratio tailored to CI devices, SRMR-CI). Results showed substantial variability across talkers comparing ADS and IDS for caregivers’ acoustic profiles from MFCCs and for speech intelligibility from SRMR-CI. These findings suggest that acoustic choices by individual mothers may differentially affect recoverability of intelligible words from speech signals by children with CIs, which may contribute to differences in these children’s language outcomes. [Work supported by NIH grant R01DC008581.]