Acoustic characteristics of infant-directed speech

A new study has found that the general speech patterns of mothers change when they talk to twin children when one has hearing impairment.

The study looked at families where one twin baby has hearing impairment and the other twin does not. The researchers enrolled three pairs of twins under the age of 2 and their parents. The first twin pair had normal hearing and served as a control, the second had one normal-hearing twin and one with mild hearing loss who uses hearing aids, and the third pair had one normal-hearing twin and one severely hearing-impaired twin who has a cochlear implant in one ear.

The research took place over the space of one year and at three intervals, the researchers recorded the mothers’ speech in a lab setting while they played with their children as they would normally at home. The researchers also recorded the mothers’ speech when they were talking to one of the clinicians working on the study. They collected data concerning pitch characteristics, utterance duration, pause duration, syllable numbers, and speaking rate, and then compared these results.

“Mothers produced more syllables and used a faster speaking rate and longer sentence duration in speech to normal-hearing twins compared to the other two pairs,” reports Dr Maria V. Kondaurova, from the Department of Otolaryngology at Indiana University’s School of Medicine, and co-author of the study. In cases where one twin baby was hearing impaired and the other twin was not, it was found that the mother not only talked to both babies as if they had hearing impairment but her general speech patterns also changed. “A child’s hearing loss may disrupt the natural reciprocal pattern of communication in mother-infant dyads,” Kondaurova concluded.