Under the Hood

The Mother Tongue: Moms Speak Differently When One Baby Has Hearing Impairment

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A new study, which looked at families where one twin baby is hearing impaired and the other twin is not, discovers the mother's general speech patterns change. Photo courtesy of Shutterstock.

One of the most prominent predictors of a child's future language development — and so a possible forecast of a child's overall cognitive development — is the manner in which a mother (or primary caregiver) speaks to the child while an infant. A new study, which looked at families where one twin baby is hearing impaired and the other twin is not, discovers the mother not only talks to both babies as if they are hearing impaired but her general speech patterns change as well.

“An infant's hearing loss affects not only the infant but also the caregiver's language behavior,” said Dr. Maria V. Kondaurova, the Department of Otolaryngology, Indiana University's School of Medicine, and co-author of the new study. These results, she noted, are relevant to all parents of both hearing-impaired and normal-hearing children.

Family Dynamics

To begin the study, the researchers recruited three pairs of twins under the age of 2 and their parents. One twin pair has normal hearing; the second pair has one normal-hearing twin and one mildly hearing-impaired twin, who uses hearing aids; and the final pair has one normal-hearing twin and one severely hearing-impaired twin, who has a cochlear implant in the right ear.

During the course of a year at three intervals, the researchers recorded the mothers' speech in the lab while they played with their children as they normally would do at home. Separately, the researchers also recorded each of the mothers speaking to one of the experimenters. After collecting the recordings, the researchers measured pitch characteristics, utterance duration, pause duration, syllable numbers, and speaking rate. Finally, they analyzed the data and drew comparisons.

“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,” Kondaurova said. However, when focusing on each mother's pronounciation of vowels, the team discovered all the mothers produced clearer vowels in infant-directed speech (versus adult-directed speech). All the mothers were making a greater effort to be understood when speaking with their children compared to when they talked to other adults.

“A child's hearing loss may disrupt the natural reciprocal pattern of communication in mother-infant dyads,” Kondaurova said. Though investigating hearing-impaired children, the study confirms the profound influence of each person's health and well-being on the family unit as a whole, and once again shows how a single child can impact the future development of all the siblings.

Source: Kondaurova MV, Bergeson-Dana TR, Wright NA. Acoustic characteristics of infant-directed speech to normal hearing and hearing-impaired twins with hearing aids and cochlear implants: A case study. Meeting of the Acoustical Society of America. 2014.

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