Academic journal article The Volta Review

Prelinguistic Vocal Development in Infants with Typical Hearing and Infants with Severe-to-Profound Hearing Loss

Academic journal article The Volta Review

Prelinguistic Vocal Development in Infants with Typical Hearing and Infants with Severe-to-Profound Hearing Loss

Article excerpt

Delays in the onset of canonical babbling with hearing loss are extensively documented. Relatively little is known about other aspects of prelinguistic vocal development and hearing loss. Eight infants with typical hearing and eight with severe-to-profound hearing loss were matched with regard to a significant vocal development milestone, the onset of canonical babbling, and were examined at three points in time: before, at, and after the onset of canonical babbling. No differences in volubility were noted between the two infant groups. Growth in canonical babbling appeared to be slower for infants with hearing loss than infants with typical hearing. Glottal and glide production was similar in both groups. The results add to a body of information delineating aspects of prelinguistic vocal development that seem to differ or to be similar in infants with hearing loss compared to infants with typical hearing.

Introduction

Hearing loss affects one in every 1,000 children in the United States (National Institutes of Health [NIH] Consensus Statement, 1993). Due to aggressive newborn hearing screening efforts (92% of infants in the United States are presently screened for hearing loss, according to the 2006 Centers for Disease Control and Prevention [CDC] Early Hearing Detection and Intervention [EHDI] hearing screening and follow-up survey), the average age of hearing loss identification in the United States is now considerably lower than 30 months, the age indicated as typical for diagnosis in the 1993 NIH Consensus Statement. Results from a universal newborn hearing screening study indicated that the median age of hearing loss identification was 3 months and for hearing aid fitting was 7.5 months (Dalzell et al., 2000). Programs that target and assess outcomes using prelinguistic vocal skills are, therefore, becoming increasingly crucial. An important first step in the development of these programs and outcome measures will be careful documentation of the course of prelinguistic vocal development in infants with severe-to-profound hearing loss.

Studies of prelinguistic vocal development and hearing loss are also needed because they shed light on the mechanisms of speech and language acquisition. Aspects of vocalizations that are found to be similar in infants with typical hearing (ITH) and infants with hearing loss would suggest that these aspects are robust and perhaps part of our biological heritage, whereas features that are different between ITH and infants with hearing loss would suggest that auditory perception is crucial in the development of these features.

Delays in the onset of canonical babbling in the presence of deafness (CB), consisting of well-formed syllables such as [ba] or [ni], are well-documented (see Oiler, 2000, for a review). Other aspects of prelinguistic vocal development, e.g., volubility, have been the subject of widespread speculations but have not received as much empirical attention. The present study longitudinally investigates several aspects of prelinguistic vocal development in ITH and in infants with severe-to-profound hearing loss (IHL) in order to further characterize the nature of prelinguistic vocal development and to determine whether hearing loss affects this development.

Volubility

Early reports claimed that the number of vocalizations per minute, or volubility, of IHL diminishes after 6 months of age (e.g., Lach, Ling, Ling, & Ship, 1970; Lenneberg, Rebelsky, & Nichols, 1965; Maskarinec, Cairns, Butterfield, & Weamer, 1981; Mavilya, 1972). This reduction was presumed to occur due to impoverished auditory input or due to impoverished auditory self-feedback (Fry, 1966; Whetnall & Fry, 1964). However, little empirical evidence was presented in support of the purported low volubility of IHL, and, therefore, the claim can be appropriately characterized as a speculation rather than as a finding.

A few recently conducted empirical observations of volubility and deafness have not revealed lower volubility in IHL. …

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