The Role Of Hearing In Emerging Speech Production For Children

Using Cochlear ImplantsShani Dettman2,3, Colleen Holt1, Jaime Leigh1,3 & Richard Dowell1,2,3

1. The University of Melbourne, Dept of Otolaryngology

2. The Cooperative Research Centre for Cochlear Implant and Hearing Aid Innovation

3. Cochlear Implant Clinic, Royal Victorian Eye and Ear Hospital, Melbourne, Australia

Objective

This study examined the types of emerging vocalisations, babble and word use for 42 infants using

cochlear implants.

Study Design

A within-subject repeated measures design was used. Subjects included 42 children with congenital and

pre-lingual onset of profound bilateral hearing loss, no additional oro-motor disability, cognitive delay or

language processing difficulties who used the Nucleus CI24 cochlear implant. Children were enrolled in

programs with a range of intervention strategies including aural/oral emphasis, total communication and

bilingual-bicultural approach. Five minute play samples of each child interacting with his/her parent were

recorded pre-implant and at 3, 6, 12 and 24 months post-implant.

Each child’s vocalizations were transcribed and categorized using guidelines suggested by Oller (1980;

1986) including: (1) phonation, (2) coo/goo, (3) expansion, (4) canonical babbling, (5) variegated babbling

and (6) first words. The relationships between outcome measures (number of vocalisations and emergence

of first words) and variables such as the child age at implant and mode of communication were examined.

Coding

The child’s vocalisations were transcribed and categorised using guidelines suggested by Oller (1980; 1986) and Oller and Eilers (1988) including the following 6 stages:

(1) Phonation Stage. This stage is characterised by non-systematic opening and closing of the vocal

tract, quasi-resonant nuclei (syllabic nasal sounds and undifferentiated vowel sounds) which do not make

full use of the vocal cavity as a resonating tube, and is expected to occur in normally hearing infants from 0

to 1 month of age.

(2) Coo/Goo Stage. (no examples were noted in this study) In this stage, the child uses controlled repetition

of syllabic elements with velar preference but timing is irregular at 2 to 3 months of age.

(3) Expansion Stage. This stage is characterised by systematic exploratory vocal play with many

examples of one particular category on one day and none on the next. These categories include squeals,

grunts, clicks, raspberries, ingressive and egressive phonation and some fully resonant nuclei. The child

also uses marginal babble which includes transitions between vowel and consonant elements which are not

regular at approximately 4 to 6 months of age.

(4) Canonical Babbling. Rigid timing of alternating syllabic elements characterises this stage. The child

typically alternates consonant and vowels, for example,“ba-ba-ba” at approximately 7 to 10 months of age.

(5) Variegated Babbling. In this stage, the child is able to systematically alternate different consonant

and vowel elements, for example, “bee-doo-bee-doo” and may use Gibberish (phonetic sequences with

contrastive stress) and Jargon (phonetic sequences with contrastive pitch and stress) at approximately 11 to

12 months of age.

(6) First words. First words are generally used by the normally hearing child at approximately 12

months of age. These include imitations, phonetically consistent forms (also known as vocables or

transitionals) and word attempts that are only recognised by familiar adults. Words may not be phonetically

accurate but may include expected toddler phonological process errors.

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Results

There was an expected progression in the sophistication of the subjects’ vocalisations over time (see Figure

1). The percentage of phonation stage and expansion stage utterances gradually decreased after 6

months device experience, and the babble and first word stages increased.

The average number of vocalisations (see Figure 2) used within five minutes increased from 19 pre-implant

Conclusions

Long term speech production studies are infrequently reported in the literature as the methodology (phonetic

transcription and analysis) is time consuming. This study provides clinicians with practical guidelines as to

the typical emergence of the exploration stage, babble and first words for a large group of children using

implants. At a practical level, close attention to the infants' emerging vocalizations may provide important

cues to emerging auditory capabilities, at a time when formal tests of speech perception are not yet suitable.

The data suggest that most children who receive cochlear implants at an early age progress through the

same stages of vocal and phonetic development as normally hearing infants, and are highly intelligible by 2

years post-implant.

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Acknowledgements to

Rachael Parker, Jade Frederiksen, Louisa

Cooke, and Speech Pathologists, Audiologists,

Surgeons and Administration Staff of the

Cochlear Implant Clinic, Royal Victorian Eye and

Ear Hospital, Victoria, Australia.

dettmans@unimelb.edu.au

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variegated babble first words

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Figure 1. Percentage of each type of vocalization at each stage pre and post-implant.

to 45 vocalisations in 5 minutes by 24 months post-implant. The blue minimum and maximum level bars

indicate very large variation in the number of vocalisations per sample.

The average number of words (see Figure 3) used within five minutes increased from 0.41 pre-implant to 36

words in 5 minutes by 24 months post-implant. The blue minimum and maximum level bars indicate wide

variation. One child used 11 words in five minutes pre-implant but most children used zero words. By 24

months post-implant, one child still used only one word in 5 minutes, but most children used 30 or more

words by 24 months post-implant.

Word use (see Figure 4) had already emerged pre-implant for 7% of children, 50% had words by 3 months

post-implant, 65% had words by 6 months post-implant, 95% had words by 12 months post-implant and

100% were using words by 24 months post-implant.

Figure 2. Average number of vocalizations used in 5 minutes in

samples recorded pre-implant, and 3, 6, 12 and 24 months post-implant. Blue bars show minimum and maximum levels.

Analysis

Analysis of the data indicated a number of interesting relationships. Firstly, children who were diagnosed and fitted with hearing aids/cochlear implants later tended to be enrolled in communication programs with a sign rather than oral/aural emphasis.

Secondly, children who had better pre-implant residual hearing used more words at 6 and 12 months post-implant, but the relationship between pre-implant hearing and word use was not significant at 24 months post-implant. Children who were older at the time of the recorded samples tended to have more words at 6 and 12 months, indicating speech progress due to maturity rather than device experience. By 24 months post-implant, the effects of age and pre-implant residual hearing were no longer significant. This perhaps indicates that the younger children and those with poorer pre-implant residual hearing had caught up somewhat to the others.

The prevalence of the expansion stage at 6 months post-implant was associated with 12 months post-implant but was not predictive of 24 months post-implant.

The prevalence of the word stage at 6 months post-implant was associated with words at 12 months post-implant, and words at 12 months post-implant were associated with words at 24 months post-implant, but words at 6 months were not significantly predictive of words at 24 months post-implant.

Figure 3. Average number of words used in 5 minutes in samples

recorded pre-implant, and 3, 6, 12 and 24 months post-implant. Blue bars show minimum and maximum levels.

Figure 4. Percentage of subjects using words in 5 minutes in

samples recorded pre-implant, and at 3, 6, 12 and 24 months post-implant.

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