Primary Caregivers Prosodic Input

to their children using cochlear implants.Dettman, S. J., Dowell, R. C., Brown, P. M., Cowan, R.S.C., & Blamey, P. J.

The University of Melbourne

The Cooperative Research Centre for Cochlear Implant and Hearing Aid Innovation

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

BackgroundHow does the normally developing infant learn to extract meaning from the speech of his/her primary caregivers? For the normally hearing infant, the processes underlying phonological development are not well understood. Without prior knowledge of what

a word or sentence actually is, the child must learn to represent the phonological content of words systematically and extract words from a nearly continuous acoustic stream which has enormous variation in pitch, stress, duration and linguistic environment

(Morgan & Safran, 1995). Although brief silences do occur, these are generally associated with stop consonants, not word boundaries (Martin, 1970).

There are a number of models of infant speech perception from ‘innate’ theories that suggest that the child has a pre-wired capacity for language or a language-acquisition-device to more ‘behaviourist’ theories which suggest that early speech perception

skills develop as a consequence of a stimulus response paradigm. Appropriate responses, which are attached to meaningful experiences for the child, are reinforced, while inappropriate responses or those not bound with meaningful experiences are

ignored (Olmsted, 1971).

The concept of bootstrapping refers to the child’s ability to use knowledge from one area to enhance performance in another (Owens, 1992). In a prosodic bootstrapping model of infant speech perception, prosodic cues such as pauses, final lengthening,

and falling pitch terminals are said to assist the infants organisation of the acoustic stream of speech into linguistic units (Fisher & Tokura, 1996). Prosodic cues may be used to organize phonological segments into groups and thus, delimit sentences and

words (Garnica, 1977). This theory is supported by the knowledge that even neonates are sensitive to pitch changes. Infants demonstrate a preference for child directed speech (Cooper & Aslin, 1990; 1994; Pegg, Werker & McLeod, 1992; Fernald & Kuhl,

1987), for their own native language (Mehler, 1988; Moon et al., 1993), their own mother’s voice (DeCasper & Fiefer, 1980), and specifically, their own mother’s use of child directed speech (Mehler et al., 1978).

Study Design5-minutes of play interaction between the 13 primary caregivers (in all cases the natural mother) and their two-year old children with profound

hearing loss were video recorded on two occasions pre-implant (Pre1 and Pre2) while the child was using bilateral hearing-aids and at 3months (Post3), 6 months (Post4) and 12 months (Post5) following the cochlear implant.

Two experienced speech pathologists independently reviewed each video sample at the utterance level until a decision was reached as to

whether the utterance contained a distinctive pitch transition and/or stressed word, characteristic of child directed speech. Cohen’s Kappa for inter-coder reliability for pitch and stress decisions were 0.89 and 0.91 respectively. Cohen’s Kappas for intra-coder reliability for pitch and

stress decisions were 0.77 and 0.84 respectively. The number of turns used by the primary caregiver in her speech directed to her child that

included any pitch transitions and/or stressed words was calculated for the 5-minute samples and expressed as a percentage of all turns offered to the child. To reduce the data the two pre-implant measures (Pre1 and Pre2) were also averaged and referred to as Pre-Combined

and the three post-implant measures (Post3, Post4, and Post5) were averaged and referred to as Post-Combined.

All children completed speech perception and language testing at the age of seven years (five years post-implant). Testing included open-set

word and sentence materials presented live voice audition alone. PBK and CNC word lists were scored for total words correct and phonemes

(PHON) correct. BKB sentences were scored for words correct. The Peabody Picture Vocabulary Test of receptive vocabulary was completed

Figure 2. Percentage of turns

with stress and/or pitch cues

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1987), for their own native language (Mehler, 1988; Moon et al., 1993), their own mother’s voice (DeCasper & Fiefer, 1980), and specifically, their own mother’s use of child directed speech (Mehler et al., 1978).

Child directed speech (motherese) has been described as facilitative in its pragmatic function; gaining and holding the child’s attention ((Stern, 1982), serving as a framework for the development of emotional bonds (Trevarthen, 1979, cited in Owens, 1992)

and maintaining conversation in order to provide a context for teaching language (Bruner, 1977). The literature, however, lacks an exchange of ideas on the specific acoustic functions of child directed speech. If acoustic cues are present, robust and

assistive of language learning, and are more salient in infant directed speech, we can add the role of child directed speech as an acoustic highlighter to word boundary identification. If primary caregivers who use child directed speech are providing the

acoustic cues to segmenting speech, the premise follows that primary caregivers who use less prosody may have children with language delays.

This study aimed to describe the environment provided by the primary caregiver and to determine whether it could meet the needs of young children who were learning to derive meaning from the incoming acoustic signal provided by the cochlear implant.

It was hypothesized that primary caregivers would be sensitive to the change in their child’s hearing status post-implant and would increase their use of prosodic cues accordingly. Furthermore, it was hypothesized in this study that the acoustic cues

available in the prosodic contour and character of the primary caregiver’s utterances would provide important cues to the underlying syntactic organization of utterances for young children using the cochlear implant.

(PHON) correct. BKB sentences were scored for words correct. The Peabody Picture Vocabulary Test of receptive vocabulary was completed

at yearly intervals post-implant up to an including 5-years post-implant. An age equivalent score (PPVT-Equiv) and a rate of vocabulary growth

(PPVT-Rate) were derived from these test results.

Results

Eleven out of thirteen primary caregivers increased their use of prosody in the post-implant period (Figure 1 below). The average percentage of turns where prosodic cues were present was 83.76% (range 40 – 99.78%; SD 14.00). T-test indicated that the Post-Combined mean (88.15

% of turns with prosody) was significantly higher (t = -3.30; p = 0.002) than the Pre-Combined mean (77.09 % of turns with prosody).

Repeated measures ANOVA also supported the t-test results in showing significant changes over time (F 4,48 = 5.39, p= 0.001) from pre-implant to post-implant sessions. These data support the hypothesis that the primary caregiver’s were sensitive to the change in the child’s

hearing post-implant. The majority of these primary caregivers appeared to be using their voice as an auditory marker to try to gain the child’s

attention and to cue turn taking.

Increased use of prosody by primary caregivers was associated with superior speech perception and language outcomes at 5 years post-

implant (Figure 2. right). Pearson’s Correlation analysis indicated significant associations between the percentage of turns used by the

primary caregiver that had any pitch/stress or cue and outcomes measures for all sessions (Pre2, Post3 and Post4, Pre-Combined and Post-Combined) except Pre1 and Post5. At Pre2 and Post3, the percentage of turns with any pitch/stress cue were significantly associated with

BKB (Pre2 r = 0.598, p = 0.031; Post3 r = 0.700, p = 0.008) and PHON (Pre2 r = 0.652, p = 0.016; Post3 r = 0.818, p = 0.001) and just failed

to reach significant for PPVT-Equiv (Pre2 r = 0.414, p = 0.159; Post3 r = 0.545, p = 0.054). At Post4, the percentage of turns with any pitch/stress cue were was significantly associated with all four outcome measures BKB (r = 0.710, p = 0.007), PHON (r = 0.902, p = 0.000),

PPVT-Equiv (r = 0.691, p = 0.009) and PPVT-Rate (r = 0.573, p = 0.041). At Post5, the percentage of turns with any pitch/stress cue were was

not significantly associated with any outcome measures. At Pre-Combined, the percentage of turns with any pitch/stress cue was significantly associated with PHON (r = 0.572, p = 0.041) and just failed to reach significance for BKB (r = 0.488, p = 0.091). At Post-Combined, the

percentage of turns with any pitch/stress cue was significantly associated with three outcome measures BKB (r = 0.749, p = 0.003), PHON (r =

0.861, p = 0.000), PPVT-Equiv (r = 0.602, p = 0.029) and just failed to reach significance for PPVT-Rate (r = 0.532, p = 0.061).

These results from 13 dyads provide support for the hypothesis that increased primary caregiver use of prosodic cues pre-implant, and at 3

and 6 months post-implant (Post3 and Post4 sessions) is associated with better child speech perception and language outcomes. One

possible suggestion as to the lack of association between the percentage of turns used by the primary caregiver that had pitch/stress cues and child outcomes at 12 months post-implant (Post5) concerns the time line of intervention. It is possible that the primary caregiver no longer

needed to use her voice as an auditory marker to gain and hold the child’s attention but was shifting the emphasis of her input toward linguistic

Figure 2 shows the percentage of turns offered by the primary caregiver to the child that had any pitch and/or

stress cue. Pre1 and Pre2 refer to samples recorded pre-implant. Post3 refers to samples recorded 3

months post-implant. Post4 refers to samples recorded 6 months post-implant. Post5 refers to samples

recorded 12 months post-implant. Although these data relate to the primary caregivers input pre and post-

implant, the cases have been placed in order of the child’s outcomes at five years post. Observation of the

data indicates a trend toward higher bars on the left. Primary Caregivers 11, 12, 1, 13 and 8, for example,

rarely missed an opportunity to include pitch and stress cues in their speech directed to their children. These

children obtain the highest scores on 5-year post-implant outcome measures of speech perception and

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Pre 1 Pre 2 Post3 Post4 Post5

and semantic aspects of the interaction.

children obtain the highest scores on 5-year post-implant outcome measures of speech perception and

language. In contrast (results on the right of the figure), Primary Caregivers 6, 5 and 7 used fewer turns that

included pitch and/or stress cues, These children performed more poorly on 5-year post-implant speech

perception and language outcome measures.

Figure1. Percentage of turns with stress and/or pitch cues

(pre-implant and post-implant averages)

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Child Rank

No. Age CI Comm Mode PTA Device Test Age Device Exp BKB PHON PPVT-Equiv PPVT-Rate PHON

1 1.74 A/O 123 MSP 7.42 5.67 100 90 5.8 1.195 3

2 1.76 A/O 120 Sprint 7.65 5.9 55 74 4.5 0.66 10

3 2.54 A/O 112 MSP 7.99 5.45 57 84 3.9 0.72 7

4 2.93 TC 120 Sprint 8.09 5.16 78 76 5.3 0.85 9

5 2.12 A/O 130 MSP 8.39 6.27 35 64 3.8 0.87 12

6 2.09 A/O 116 MSP 7.12 5.03 87 72 3.9 0.9 11

7 1.78 A/O 125 MSP 5.96 4.18 10 31 2.3 0.34 13

8 1.75 A/O 113 Sprint 6.96 5.21 78 87 4.4 1.189 5

9 1.73 TC 110 Sprint 6.91 5.18 72 79 3.7 0.56 8

10 2.48 A/O 117 Sprint 7.54 5.06 80 84 6.1 1.39 6

11 1.44 A/O 105 Sprint 6.58 5.14 100 93 6.6 1.03 1

12 1.54 A/O 113 Sprint 6.43 4.88 92 92 6.1 1.05 2

13 2.12 A/O 125 Sprint 8.29 6.17 90 88 4 0.55 4

mean 2 117.62 7.33 5.33 71.85 78 4.65 0.87

min 1.44 105 5.96 4.18 10 31 2.3 0.34

max 2.93 130 8.39 6.27 100 93 6.6 1.39

Demographics Speech Perception Language

Table 1 (above) shows the individual demographic details for 13 child participants, speech perception and language outcome measures at

5-years post-implant. The rank order is given for the open set word test scored for phonemes correct (PHON).

ConclusionsIn speech directed to their children using the cochlear implant, most of the primary caregivers in this study increased their use of pitch and/or

stress cues in the post-implant period. The prevalence of the primary caregiver’s prosodic cues pre-implant and in the first 12 months of

device use post-implant was associated with better child communication outcomes at five years post implant. It is suggested that these

types of acoustic cues, in addition to semantic, linguistic and pragmatic features of the child directed speech may have facilitated the child’s

learning to listen. In research cause and effect cannot be determined even if high correlations between variables are found, but the relative

importance of parental input and particular parental strategies may be isolated and form the basis for prospective empirical research.

Often I find I have to do something clever to get a child’s attention. Often I find I have to do something clever to get a child’s attention. Often I find I have to do something clever to get a child’s attention. Often I find I have to do something clever to get a child’s attention.

And it’s more effective to do something completely ridiculous or out of the ordinary.And it’s more effective to do something completely ridiculous or out of the ordinary.And it’s more effective to do something completely ridiculous or out of the ordinary.And it’s more effective to do something completely ridiculous or out of the ordinary.

Anything that departs from the ordinary or expected. Anything that departs from the ordinary or expected. Anything that departs from the ordinary or expected. Anything that departs from the ordinary or expected.

That gets their attention best. That gets their attention best. That gets their attention best. That gets their attention best.

(from interviews with mothers, Garnica, 1977, p. 88)(from interviews with mothers, Garnica, 1977, p. 88)(from interviews with mothers, Garnica, 1977, p. 88)(from interviews with mothers, Garnica, 1977, p. 88)

Acknowledgements to the staff and patients of the Cochlear Implant Clinic, Royal Victorian Eye and Ear Hospital, Melbourne, Australia.

dettmans@unimelb.edu.au

Figure 1 shows the percentage of turns offered by the primary caregiver to the child that had any pitch

and/or stress cue. These data are the same as those presented in Figure 2 but have been reduced to

simplify the visual information. The two pre-implant measures (Pre1 and Pre2) were averaged and referred

to as Pre-Combined and the three post-implant measures (Post3, Post4, and Post5) were averaged and

referred to as Post-Combined.

All primary caregivers except Case 9 and Case 4 increased their use of pitch and stress in the post-implant

period.

Primary Caregiver 9 and 4 attended an early intervention centre with their children that had a total

communication emphasis. All other primary caregivers were attending early intervention centres with an

aural/oral emphasis at the time of the video-recording. Primary Caregiver 7 shifted her child to an early

intervention centre with a total communication emphasis after two years of cochlear implant use.

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Pre-Combined Post-Combined

SD 0.43 7.05 0.75 0.57 26.43 16.53 1.24 0.3