See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/14898721

Infant vocalizations and the early diagnosis of severe hearing impairment

ARTICLE in JOURNAL OF PEDIATRICS · MARCH 1994 Impact Factor: 3.79 · DOI: 10.1016/S0022-3476(94)70303-5 · Source: PubMed

CITATIONS READS 74 80

2 AUTHORS, INCLUDING:

D. Kimbrough Oller The University of Memphis

170 PUBLICATIONS 3,028 CITATIONS

SEE PROFILE

Available from: D. Kimbrough Oller Retrieved on: 02 March 2016 Infant vocalizations and the early diagnosis of severe hearing impairment

Rebecca E. Eilers, PhD, and D. Kimbrough Oiler, PhD From the Mailman Center for Child Development and the University of Miami Ear Institute, De- partments of Psychology, Pediatrics, and Otolaryngology, University of Miami, Miami, Florida

To determine whether late onset of canonical babbling could be used as a cri- terion to determine risk of hearing impairment, we obtained vocalization sam- ples longitudinally from 94 infants with normal hearing and 37 infants with severe to profound hearing impairment. Parents were instructed to report the onset of canonical babbling (the production of well-formed syllables such as "da," "na," "bee," "yaya"). Verification that the infants were producing canonical syllables was collected in laboratory audio recordings. Infants with normal hearing produced canonical vocalizations before 11 months of age (range, 3 to t0 months; mode, 7 months); infants who were deaf failed to produce canoni- cal syllables until tt months of age or older, often well into the third year of life (range, tt to 49 months; mode, 24 months). The correlation between age at an- set of the canonical stage and age at auditory amplification was 0.68, indicat- ing that early identification and fitting of hearing aids is of significant benefit to infants learning language. The fact that there is no overlap in the distribution of the onset of canonical babbling between infants with normal hearing and infants with hearing impairment means that the failure of otherwise healthy in- fants to produce canonical syllables before 1-1 months of age should be consid- ered a serious risk factor for hearing impairment and, when observed, should result in immediate referral for audiologic evaluation. (J PEDIATR 1994;124:199- 203)

Undiagnosed hearing loss in infancy is not uncommon; the group of infants at very high risk for severe hearing impair- average age of diagnosis in the United States approaches 3 ment during the first year of life. Infants with severe to pro- years. 1 Referral by pediatricians for audiologic evaluation found hearing losses fail to produce canonical (well-formed) sometimes occurs only after repeated requests by parents, babbling before I 1 months of age, whereas infants with or after recognition of late onset of meaningful speech dur- normal hearing almost always babble canonically before 11 ing the second or third year of life. Consequently, infants months of age. 2 The absence of this easily recognized vocal often are not provided with hearing aids or other habilita- behavior can serve as a diagnostic marker of hearing tire devices during a key period in which language is nat- impairment years before the failure of the appearance of urally acquired. It is possible, however, to identify a small normal speech. Infants with normal hearing produce vocalizations in Supported by grants from the National Institutes of Health/Na- stages of development that have been described by Stark 3 tional Institute of Child Health and Development (No. 5 R01 and Oller. 4, 5 These stages reveal step-by-step progress in DC00484; Dr. Oller) and from the U.S. Department of Education/ the vocal capacities required for the production of speech- National Institute on Disability and Rehabilitation Research (No. H133 G10118; Dr. Eilers). like syllables. Four clear stages can be discerned, the last of Submitted for publication June 22, 1993; accepted Aug. 30, 1993. which, the canonical stage, marks the onset of mature Reprint requests: Rebecca E. Eilers, PhD, Mailman Center for (well-formed) syllables that appear commonly between 5 Child Development, PO Box 016820, Miami, FL 33101. and 8 months of age. Once the infant reaches the canonical Copyright ® 1994 by Mosby-Year Book, Inc. stage, he or she typically produces strings of syllables that 0022-3476/94/$3.00 + 0 9/20/51165 are so speechlike that parents often assert that the infant is

199 2 0 0 Eilers and Oiler The Journal of Pediatrics February 1994 talking. These syllables are not used referentially (i.e., in were recruited by mail solicitation to participate in a study association with word meaning) or instrumentally during of vocal development. Only infants with unremarkable per- the middle of the first year of life. However, the syllables do inatal and postnatal histories were studied. Twenty-one in- meet the phonetic requirements of well-formed speech fants were preterm. Selection criteria for the preterm sounds in any of the world's spoken languages. infants included birth weight between 1400 and 2100 gm Early claims that auditory experience has little effect on and absence of either congenital defects or prenatal or early vocal behavior of infants 6 have been replaced by ev- postnatal complications. Infants were excluded if they had idence that auditory experience appears to be critical to the evidence of intraventricular hemorrhage, hypoxia, respira- development of mature syllables. Infants who are deaf have tory distress syndrome, severe hyperbilirubinemia, or other significant delay in the onset of canonical stage vocaliza- medical complications requiring significant medical inter- tions.2, 7-10 Furthermore, there appear to be consistent dif- vention, or if their 5-minute Apgar score was less than 7. All ferences in precanonical vocalizations of deaf infants and ages for preterm infants were corrected for duration of ges- hearing infants, ll as well as different sound production pre- tation. Gestational age estimates were based on postnatal ferences once the canonical stage is reached. 1°, 12 examinations15, 16 and yielded a mean age at birth of 33 The differences observed between the vocalizations of weeks (range, 28.5 to 35 weeks). The mean birth weight of hearing infants and deaf infants are not subtle; rather, they the preterm infants was 1820 gm (range, 1446 to 2070 gm). are salient and striking. The onset of the canonical stage Subjects with hearing impairments. Thirty infants with virtually always occurs by 10 months of age in normally de- varying levels of hearing impairment ranging from pro- veloping hearing infants; no deaf infant has yet been found found (> 100 dB better-ear pure-tone average) to severe (80 to begin the canonical stage before 11 months, and often the to 90 dB better-ear pure-tone average) were recruited from onset is much later. 2 Other infants who have near-normal an infant-parent educational program for the hearing audition but pervasive developmental delay (e.g., infants impaired. Of the 30 infants, 27 had been identified at birth with Down syndrome) have a slight delay in the onset of the through a screening program for infant hearing 17 (Infant canonical stage but overlap considerably with normally de- Hearing Impairment Program, Children's Medical Service, veloping infants in age at onset. 13 Healthy infants born pre- State of Florida, administered through the University of maturely, as well as infants in families of low socioeconomic Miami and Jackson Memorial Hospital). For the youngest status, have no delay in onset of the canonical stage. 14 children, hearing loss estimates were based on auditory Despite the striking differences between normally devel- brain-stem response testing alone, with absence of a re- oping and hearing-impaired infants, few deaf infants have sponse at 95 dB nHL (normal hearing level) assumed to in- been studied extensively and relatively small numbers of dicate a loss in the profound range. hearing infants have been evaluated longitudinally for Additional subjects. In addition to the subjects previ- comparison purposes. In our earlier work we reported a ously described, seven infants with hearing impairments longitudinal evaluation of 21 hearing infants and 7 deaf in- and 21 normally developing infants from our previous fants who were followed during the first 2 years of life, pro- study2 were included in the analyses. Data from these viding enough detail to determine accurately the age at on- infants were collected in a fashion similar to data from the set of the canonical stage. 2 Since that time we have enlarged new group of infants. Because of the rarity of detailed our sample considerably to include additional deaf infants records of deaf and hearing infants' vocalizations, it seemed and hearing infants, many of whom were born prematurely important to describe the results for as many infants as and others of whom were from families of low socioeco- possible. (A table listing the cause, age at identification of nomic status. We hypothesized that the onset of canonical hearing impairment, age at fitting with hearing aid, and babbling is robust, appearing reliably before 11 months of level of hearing loss of both groups of hearing-impaired age in hearing infants, regardless of gestational age at birth subjects is available from the authors.) or socioeconomic status. The specific purpose of the study Sampling and recording procedures. The term infants was to determine whether late onset of canonical babbling with normal hearing were seen every other week, and the could be used as a criterion to determine risk status for preterm infants were seen monthly by project staff mem- hearing impairment during routine well-baby visits during bers. In addition, each infant had laboratory evaluation on the first year of life. 5 consecutive days after the parent-designated onset of the canonical stage to ensure accuracy of age at onset assigned METHODS to each infant. 3, 18, 19 Parents had been taught to recognize Subjects canonical babbling and had been instructed to call the Normally hearing subjects. Seventy-three infants were project staff as soon as it was noted. Canonical syllables followed longitudinally from the age of 2 months. Infants were described as instances of infants' "talking" but with- The Journal of Pediatrics Eilers and Oller 2 0 1 Volume 124, Number 2

® • 0 @ • O0O O0O 0O0 0@0 000 I! Legend -'/ 000 • Full term hearing infant 000 000 Preterm hearing infant 000 Deaf infant 000 000 Deaf nfant not yet canon cal) @000 00000 00000 @0000 00000 00000 00000 • 0000000 [] • [] 0000000 • • [] • • [] II • oeeeeeOell II IIi IIIIIIID II IIII • • • I I I | I I I I I I I I I I I I I i I i i I I I 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 Months of Age

Fig. t. Onset of canonical babbling in severely to profoundly hearing-impaired infants and in hearing infants. Data on preterm infants are shown at corrected ages.

out meaning, using well-formed syllables or sequences of bles as soon as they occurred. The specification of the onset syllables. Examples of "dada," "meme," "baba," "ma," of the canonical stage was more difficult for the infants with and "ya" were given. After notification by a parent or iden- hearing impairments than for the infants with normal tification of canonical babbling during a monthly visit, the hearing. Five of the infants with hearing impairments had infant's vocalizations were recorded for stage verification. not reached the canonical stage by the time of this report, Each recording session was 20 to 30 minutes in duration and although they were older than 12 months of age. Some in- consisted of the infant's interacting with project staff and ac- fants with hearing impairments had an erratic onset of the companying family members in a sound-treated room. An canonical stage, producing canonical syllables on some days attempt was made to obtain a minimum of 50 utterances per but failing to produce them in subsequent samples, or pro- recording. If the 50-utterance minimum was not reached, or ducing them with lower frequency than infants with normal if the parent reported that the vocalizations were atypical hearing in the canonical stage. Nevertheless, for the pur- of the infant, the session was rescheduled. Infants were des- poses of this study, once canonical syllables occurred, even ignated to be in the canonical stage if, and only if, repeated erratically, infants with hearing impairments were said to occurrences of canonical syllables were observed during 5 be in the canonical stage. Thus the criterion for stage consecutive days after onset. In all but two cases, parental assignment was more stringent for the infants with normal reports were verified in the laboratory evaluations. In two hearing than for the infants with hearing impairment. cases, canonical babbling was documented by project staff at a later time than at the initial report. Parents proved to RESULTS be reliable and timely informants concerning their infants' Figure 1 illustrates that each of the 94 preterm or term use of canonical syllables. infants with normal hearing began canonical babbling be- The vocalizations of infants with hearing impairments fore 11 months of age. The onset of canonical babbling for were also recorded monthly by the same procedures as pre- infants with normal hearing ranged from 3 to 10 months viously outlined. In addition, most of the infants with hear- (mode, 7 months). In contrast, none of the 37 infants with ing impairments were enrolled in either a parent-infant ed- hearing impairment had an age at onset of the canonical ucational program for the hearing impaired or a full-day stage before 11 months of age. The onset of canonical bab- educational program. In either case, the infants were seen bling for infants with hearing impairment ranged from 11 either weekly or daily by a speech therapist. Vocalization to 49 months (mode, 24 months). Thus there was no over- samples were collected in the context of these programs, and lap in the distribution of onset of canonical babbling for deaf the speech therapists reported the onset of canonical sylla- infants and hearing infants, despite the fact that the crite- 2 0 2 Eilers and Oller The Journal of Pediatrics February 1994

50 o) r- _Q _0 40- O

O A • 0 c- 30 • 6-O o C) 20-

c- [] o f~• ProfoundLegendHearing Loss I 10 ~ Severeto Profound /

0 0 10 20 30 40 Age Aided in Months Fi9. 2. Relation between age at onset of canonical babbling and age at auditory amplification in hearing-impaired in- fants and young children.

rion for assignment was more lax for infants with hearing ing impairment is correlated with age at amplification and impairment and that these infants were fitted with hearing intervention, suggesting that early identification may be aids and received consistent, high-quality early interven- critical to successful language acquisition. tion. Although universal newborn hearing screening has been Figure 2 illustrates the relation between the age at onset recommended by the National Institutes of Health Con- of canonical babbling and the age at amplification in 28 of sensus Conference, 1 hearing screening is still limited, and the 37 infants with hearing impairment in the study. Nine typically only high-risk infants are screened. Fully half of infants were not included in this analysis, five because they all infants with hearing impairments do not have neonatal have not yet reached the canonical stage, three (including or historical risk factors at the time of screening and are thus one with meningitis-induced deafness) because the onset of missed.1 The results of this study suggest that infant vocal- the canonical stage preceded amplification, and one because izations may play an important role in the assessment of in- of late-onset deafness caused by meningitis. The illustration fant hearing during the first year of life, because a large shows that there was a systematic relation between age at number of infants receive no hearing screening, and the pe- onset and age at amplification. A statistical analysis of the diatrician may use the lack of canonical vocalizations as an relationship yielded a Pearson product moment correlation indicator to refer infants with suspected severe to profound of 0.68 (p <0.0001). hearing loss by the time they reach 11 months of age. In- fants who do not, by parental report, produce canonical syl- DISCUSSION lables by 11 months should be referred for audiologic eval- The key results of this study are as follows: (1) infants uation. Such referral may result in identification of hearing with severe to profound hearing impairment are signifi- impairment nearly 2 years earlier than the average age at cantly delayed in the onset of canonical babbling, a precur- diagnosis in the United States. 1 sor to the development of meaningful speech; (2) there is no Pediatricians may delay referrals for audiologic assess- overlap in onset distribution of canonical babbling between ment even when given parental reports of an infant's fail- hearing-impaired and normally hearing infants, and the ure to develop early language (first words and primitive failure of canonical babbling to start may be taken as a sentences). The pediatrician's hesitation is often based on marker of extreme risk of severe to profound hearing knowledge of the large individual differences in language impairment; (3) parents are good informants regarding development in normally developing infants and young their infants' ability to produce canonical syllables; and (4) children. Language delays may, in fact, be based on a wide the attainment of the canonical stage in infants with hear- variety of factors in addition to hearing loss. To our knowl- The Journal of Pediatrics Eilers and Oiler 2 0 3 Volume 124, Number 2 edge, delays in the onset of canonical babbling beyond 11 6. Lenneberg EH, Rebelsky GF, Nichols IA. The vocalizations of months of age, however, rarely occur in otherwise normally infants born to deaf and hearing parents. Hum Dev 1965;8:23- 37. developing infants and are of sufficient concern to warrant 7. Kent RD, Osberger M J, Netsell R, Hustedde CG. Phonetic immediate audiologic evaluation by means of conditioned development in identical twins who differ in auditory function. behavioral techniques such as visual reinforcement audi- J Speech Hear Dis 1987;52:64-75. ometry20, 21 and, if necessary, auditory brain-stem response 8. Oiler DK, Eilers RE, Bull DH, Carney AE. Prespeech vocal- audiometry.20. 21 Prompt identification by the first birthday izations of a deaf infant: a comparison with normal metapho- nological development. J Speech Hearing Res 1985;28:47-63. will allow the child to benefit from early amplification and 9. Stoel-Gammon C. Prelinguistic vocalizations of hearing-im- intervention, and will maximize the child's potential for oral paired and normally hearing subjects: a comparison of conso- language development by aiding the child during the period nantal inventories. Journal of Speech and Hearing Disorders in which language is normally learned. 1988;53:302-15. Although early infant vocal behavior often provides a 10. Stoel-GaInmon C, Otomo K. Babbling development of hear- ing-impaired and normally hearing subjects. Journal of Speech window from which to observe severe to profound hearing and Hearing Disorders 1986;51:33-41. loss, it is not yet clear how less severe losses might affect ca- 11. Oller DK, Bull DH. Vocalizations of deaf infants. Presented nonical babbling. It is probable that less severe losses are at the International Conference on Infant Studies, New York, less disruptive of normal vocal development; thus the infant 1984. with moderate hearing impairment may not appear to have 12. Stark RE. Some features of the vocalizations of young deaf infants. In: Bosma JF, ed. The mouth of the infant. Springfield, delayed onset of babbling and yet may have significant de- Illinois: CharLes C Thomas, 1972:431-41. lays in speech and language development. 1 Similarly, 13. Steffens ML, Oiler DK, Lynch MP, Urbano RC. Vocal devel- infants with progressive, slow-onset losses (such as those opment in infants with Down syndrome and infants who are often associated with cytomegalovirus infection) or late-oc- developing normally. Am J Ment Retard 1992;97:235-46. curring losses (such as those associated with meningitis) 14. Eilers RE, Oller DK, Levine S, Basinger D, Lynch MP, Ur- bano R. The role of prematurity and socioeconomic status in may not be identified if only canonical babbling is used to the onset of canonical babbling in infants. Infant Behavior and assess risk. Consequently, it is important for all infants to Development 1993;16:297-315. be screened for hearing loss early in the second year of 15. Dubowitz LM, Dubowitz V, Goldberg C. Clinical assessment life--or sooner if risk factors associated with hearing loss of gestational age in the newborn infant. J PEDIATR 1970; have been identified. 77:1-10. 16. Ballard JL, Novak KK, Driver M. A simplified score for assessment of fetal maturation of newly born infants. J PEDI- We thank T. J. Balkany, MD, and E. Bancalari, MD, for their ATR 1979;95:769-74. helpful comments, and Lynn W. Miskiel and Barbara J. Lewis for 17. Filer R, Gonzales L. Children's Medical Service Report: Uni- their help in assessing the infants with hearing impairment. versity of Miami Infant Hearing Impairment Screening Pro- gram, July 1991. 18. Zlatin M. Explorative mapping of the vocal tract and primi- REFERENCES tive syllabification in infancy: the first six months. Presented at 1. National Institutes of Health Consensus Development Con- the American Speech and Hearing Association Convention, ference. Early identification of hearing impairment in infants Washington, D.C., 1975. and young children. Bethesda, Maryland: National Institutes 19. Smith BL, Oiler DK. A comparative study of premeaningful of Health, 1993. vocalizations produced by normal and Down's syndrome 2. Oiler DK, Eilers RE. The role of audition in infant babbling. infants. Journal of Speech and Hearing Disorders 1981 ;46:46- Child Dev 1988;59:441-9. 52. 3. StarkRE. Stages °f speech devel°pment in the first year °flife" 20. Eilers RE, Ozdamar (5, Steffens ML. Classification of audio- In: Yeni-Komshian G, Kavanagh J, Ferguson C, eds. Child grams by sequential testing: reliab!lity and validity of an au- phonology; vol 1. New York: Academic Press, 1980173-90. tomated behavioral hearing screening algorithm. J Am Acad 4. Oiler DK. Infant vocalization and the development of speech. Audiol 1993;4:172-81. Allied Health and Behavioral Sciences 1978;1:523-49. 21. Wilson WR, Moore JM, Thompson G. Sound-field auditory 5. Oiler DK. The emergence of the sounds of speech in infancy. thresholds of infants utilizing visual reinforcement audiometry In: Yeni-Komshian G, Kavanagh J, Ferguson C, eds. Child (VRA). Presented at the American Speech and Hearing As- phonology; vol 1. New York: Academic Press, 1980:93-112. sociation Convention, Houston, Texas, 1976.