Phonetic Development in Identical Twins Differing in Auditory Function The subjects of this report are identical (monozygotic) twin boys who differ in auditory function. One has normal hearing; the other has a profound hearing loss bilaterally. These boys offered a rare opportunity to study the effects of hearing loss on vocal development with reasonable control over environmental and genetic ... Reports
Reports  |   February 01, 1987
Phonetic Development in Identical Twins Differing in Auditory Function
 
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Article Information
Reports   |   February 01, 1987
Phonetic Development in Identical Twins Differing in Auditory Function
Journal of Speech and Hearing Disorders, February 1987, Vol. 52, 64-75. doi:10.1044/jshd.5201.64
History: Received March 10, 1986 , Accepted July 8, 1986
 
Journal of Speech and Hearing Disorders, February 1987, Vol. 52, 64-75. doi:10.1044/jshd.5201.64
History: Received March 10, 1986; Accepted July 8, 1986

The subjects of this report are identical (monozygotic) twin boys who differ in auditory function. One has normal hearing; the other has a profound hearing loss bilaterally. These boys offered a rare opportunity to study the effects of hearing loss on vocal development with reasonable control over environmental and genetic factors. This initial report focuses on their vocal development over the sampled ages of 8, 12, and 15 months. Acoustic-phonetic differences in the babbling of the two boys were evident in the 8-month sample (the first recording opportunity), and some differences between them became greater over the succeeding samples at 12 and 15 months. The major differences were in (a) the formant patterns of vocalic elements; (b) the frequency of occurrence of fricatives, affricates, and trills; (c) histograms of syllable type; and (d) variation in vowel usage. The data hold implications for the early identification of infants at risk for communication disorder and for the understanding of auditory-motor processes in phonetic development during infancy.

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