1. The Role Of Hearing In Emerging Speech Production For Children
Using Cochlear Implants
Shani 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
Coding
This study examined the types of emerging vocalisations, babble and word use for 42 infants using
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:
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.
100%
(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.
80%
60%
Results
40%
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.
20%
0%
Pre Implant 3 mo post 6 mo post 12 mo post 24 mo post
phonation
variegated babble
expansion
first words
canonical babble
Figure 1. Percentage of each type of vocalization at each stage pre and post-implant.
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.
100
60
40
20
0
100
P e rc e n ta g e o f s u b je c ts
u s in g w o rd s
80
N u m b e r o f W o rd s
( u s e d in 5 m in )
N u m b e r o f V o c a l is a t io n s
( u s e d in 5 m in )
100
The average number of vocalisations (see Figure 2) used within five minutes increased from 19 pre-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.
80
60
40
20
0
Pre implant 3 mo post 6 mo post 12 mo post 24 mo post
Pre implant 3 mo post 6 mo post 12 mo post 24 mo post
80
60
40
20
0
pre implant 3 mo post 6 mo post 12 mo post 24 mo post
Figure 2. Average number of vocalizations used in 5 minutes in
Figure 3. Average number of words used in 5 minutes in samples
Figure 4. Percentage of subjects using words in 5 minutes in
samples recorded pre-implant, and 3, 6, 12 and 24 months postimplant. Blue bars show minimum and maximum levels.
recorded pre-implant, and 3, 6, 12 and 24 months post-implant. Blue
bars show minimum and maximum levels.
samples recorded pre-implant, and at 3, 6, 12 and 24 months postimplant.
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 postimplant, 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.
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.
Acknowledgements to
The prevalence of the expansion stage at 6 months post-implant was associated with 12 months postimplant 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 postimplant, 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.
™
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