Vocal matching in interactions between mothers and their normal-hearing and hearing-impaired twins

Vocal matching, the ability to imitate properties of speech, was examined in interactions between mothers and their normal-hearing (NH) and hearing-impaired twins who used hearing aids (HAs) or a cochlear implant (CI). Vocalizations of three mother-twin triads were recorded in three sessions over 12 months. In one triad, the twins were 15.8 months old and NH. In another triad, the twins were 11.8 months; one was NH while the other had HAs. In the third triad, twins were 14.8 months; one was NH while the other had a CI. A vocal match was defined as an instance of perceptual similarity between adjacent maternal and infant utterances in relation to pitch contour, utterance duration, rhythm, or vowels and consonants. Reciprocal vocal matching by both partners occurred in 14-62% of vocalizations across triads. At session three, CI and HA infants’ and mothers’ reciprocal matches increased compared to the two previous sessions and to the NH dyads; reciprocal matches in the NH dyads decreased over time. The results suggest vocal matching is part of linguistic interactions between mothers and their NH and hearing-impaired infants and that early amplification facilitates mothers’ and infants’ matching.