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. Author manuscript; available in PMC: 2011 Nov 8.
Published in final edited form as: Ear Hear. 1998 Aug;19(4):310–318. doi: 10.1097/00003446-199808000-00006

The Production of English Inflectional Morphology, Speech Production and Listening Performance in Children with Cochlear Implants

Linda J Spencer 1, Nancy Tye-Murray 1, J Bruce Tomblin 1
PMCID: PMC3210819  NIHMSID: NIHMS332228  PMID: 9728726

Abstract

Objective

To compare how children who use either cochlear implants (CIs) or hearing aids (HAs) express English inflectional morphemes during conversation, i.e., with voice, with sign, or with both. A secondary objective was to investigate the relationship between morpheme use in pediatric CI users and their speech perception skills, length of experience with the device, and accuracy of phoneme production.

Design

Group 1 consisted of 25 children who used CIs, and Group 2 consisted of 13 children who used HAs. All children were prelingually deafened and all used simultaneous communication. A 12 minute spontaneous conversation was elicited, transcribed and coded. Between group comparisons were performed to evaluate differences in modality and number of morphemes used. Additionally, use of morpheme endings was related to length of CI experience, accuracy of phoneme production, and closed-set speech recognition performance.

Results

Children who had CI experience produced significantly more English inflected morphemes than children in the HA group. CI participants also expressed the inflected endings by using voice-only mode 91% of the time, whereas HA participants used voice-only mode 1% of the time. In the CI group, a strong relationship was found between number of morpheme endings used and speech recognition scores, length of CI experience and accuracy of phoneme production. The results of this study indicate that input from the CI facilitates children's ability to perceive and comprehend bound morphemes.

This investigation focused on the use of English inflectional morphology by young cochlear implant (CI) users who communicate primarily with Signed English. Our goal was to evaluate the acquisition of inflectional endings, and to explore the role of CI use in their development. The first section of the following review indicates that little research exists concerning the language skills of young CI users. In the next sections, we note that these children often acquire the speech skills necessary to produce the sounds associated with plurals and third person possessive, /s, z/, past tense /t, d/, as well as the /m/ associated with first person possessive (i.e., I'm), and the /ng/ associated with the present progressive tense. As will be noted, CI children can often hear these sounds, so they may receive exposure to them during everyday listening.

Language

Few studies to data have investigated the language skills of CI users. The current literature is limited by small sample sizes, mixed samples of children with prelingual and postlingual deafness, and pools of participants who utilized different educational methods or communication modalities. Nevertheless, there are indications that use of a CI may affect language development (Hasenstab & Tobey, 1991; Robbins, Osberger, Miyamoto, & Kessler, 1995).

Improvements in receptive and expressive vocabulary and syntax skills often follow receipt of a CI (Geers & Moog, 1994; Miyamoto, Osberger, Robbins, Myres, Kessler, & Pope, 1992). For instance Miyamoto et al. (1992) reported small improvements in receptive vocabulary in a group of children after they used a CI for 2.5 yr as indexed by quotient scores on the Peabody Picture Vocabulary Test-Revised (Dunn & Dunn, 1981). Geers and Moog (1994) reported that after 3 yr of devise use, children who used CIs performed better than children who used hearing aids (HAs) on the receptive language test, Rhode Island Test of Language Structure (Engen & Engen, 1983). Conversely, expressive language test results did not reveal a statistically significant group difference.

No studies have focused specifically on the use of morphological endings by CI users. However much research suggests that deaf children who use HAs tend not to use morphological endings, or tend to use them inappropriately(Cooper, 1967; Crandall, 1978; Gaustad, 1986; Quigley & Paul, 1990). For instance, Bornstein, Salunier, and Hamilton (1980) examined the use of inflectional endings (in either sign-only mode or voice-and-sign mode) by 20 young HA users over a 4 yr time period. At an average age of 47.6 mo, the children used no endings. Four yr later, the percent of inclusion was better, albeit delayed. The children were least likely to use third person singular endings (11% of the time when use would be appropriate) and most likely to use regular plural endings (67%). There is some evidence that the developmental order for morpheme endings may be the same for deaf children who use Signed English and for hearing children, although deaf children may be more inconsistent in their use (Crandall, 1978: Schick & Moeller, 1992). Signed English generally has one sign to denote one meaning, using primarily American Sign Language (ASL) signs in English word order. Compound and complex words are formed by adding invented signs and endings to form one word (see Wilbur, 1987).

One factor that contributes to morphological deficits may be that most deaf children cannot articulate the sounds necessary to convey the endings. For example, many children are unable to articulate an /s/ or distinguish between /t/ and /d/ (Smith, 1975). They may not produce these language structures in part, because they cannot speak them.

Perhaps more importantly, deaf children who use HAs may not receive models of many inflectional endings during every day conversation, and therefore, do not incorporate them into their own language outputs. For instance, young HA users often cannot hear the low-intensity, high-frequency sounds such as /s, z/, and low-frequency, low-intensity sounds such as /m, n, ng/. They thus may not be aware of when the endings occur in everyday speech, particularly because many people often omit inflected endings when using Signed English (Kluwin, 1981; Marmor & Pettito, 1979).

Recent evidence suggests that CI children may not have as extensive production and perceptual difficulties. Next, we will briefly review some of this evidence.

Speech Production

As a group, children who use CIs demonstrate improved speech production skills (Osberger, Maso, & Sam, 1993; Tobey, Geers, & Brenner, 1994; Tobey & Hasenstab, 1991; Tobey, Pancamo, Staller, Brimacombe, & Beiter, 1991; Tye-Murray & Kirk, 1993; Tye-Murray, Spencer, & Woodworth, 1995). For instance they tend to increase their imitative and spontaneous phonetic repertoires and consonant features, and improve overall speech intelligibility (Osberger, Robbins, Berry, Todd, Hesketh, & Sedey, 1991, Osberger, Robbins, Todd & Riley, 1994). In one study, Tobey et al. (1994) reported that children who use CIs imitated vowels and consonants better than children who used HAs and who had similar hearing losses.

Speech Perception

Two yr postimplantation, children with prelingual deafness may demonstrate improved pattern recognition, improved word and phoneme identification, and in some cases, open-set word recognition (Fryauf-Bertschy, Tyler, Kelsay, & Gantz, 1992; Fryauf-Bertschy, Tyler, Kelsay, Gantz & Woodworth, 1997; Miyamoto, Osberger, Robbins, Myres, & Kessler, 1993; Staller, Beiter, Brimacombe, Mecklenburg, & Arndt, 1991). There is some evidence that a CI provides information that allows children to perceive the segments of the speech signal that correspond to inflectional endings. Tye-Murray, Tyler, Woodworth, and Gantz (1992) performed an information transmission analysis on initial position consonant recognition errors of adult CI users. The adults utilized the nasality feature relatively well and had some ability to recognize the frication feature. Tye-Murray, Spencer, and Gilbert-Bedia (1995) performed a comparable study with children who use CIs. The children achieved highest accuracy recognizing the nasality feature, and lowest for the place feature. They were able to utilize some information about frication. Interestingly, those children who perceived these features were likely to speak them accurately, whereas those children who did not perceive them were likely to err in producing them. This finding suggests that access to the acoustic signal can influence speech production. In this investigation, we will extend this finding to suggest that access to the acoustic signal can influence language use in specific ways as well.

Purpose

Children who use CIs and benefit from auditory speech input may perceive and produce the phonemes that comprise inflected endings better than children who are deaf and use HAs, or children who use CIs but receive little benefit. They may therefore follow a different pattern with respect to inflected morpheme acquisition and production.

In this investigation we compared the communication mode (i.e., voice-only, sign-only, or voice-and-sign) used to produce English inflectional morphology in two groups of children with prelingual profound deafness: CI users and HA users. Both groups communicated primarily with Signed English. We also examined the relationship between speech production, speech perception and the expressive development of English inflected endings in children CIs. The following questions were addressed:

  1. Do young CI users produce inflected endings differently than HA users, as indexed by measures of frequency of occurrence and mode of communication?

  2. Is there a relationship between speech perception skill and use of inflected endings?

  3. Does the duration of CI experience relate to accuracy of phoneme production and use of inflected endings?

Methods

Participants

Twenty-five children who were prelingually deaf and who had a minimum of 2 yr of CI experience at the time of testing, and 13 children who were prelingually deaf and wore HAs participated in this study. Demographic data are presented in Table 1. All of the children were identified as being deaf before 18 mo of age, with the exception of participants CI4 and CI19 who were 30 mo and 26 mo, respectively. They demonstrated limited verbal language skills and their functional communication skills at the time of implant surgery were similar to the test group. Participants were assigned an identification number.

TABLE 1.

Individual demographic information for participants who use a cochlear implant (CI) or a hearing aid (HA).

Participant Months of CI Experience Age at Testing (Mo) Age Loss First Noted by Parenis (Mo) Age at CI Hookup (Mo) Etiology Encoding Strategy Number of Electrodes
CI1 35 67 9 31 Meningitis Mpeak 21
CI2 36 93 14* 57 Unknown Mpeak 20
CI3 48 106 12* 58 Unknown F0F1F2 22
CI4 36 96 30 60 Meningitis Mpeak 11
CI5 43 99 12 51 Meningitis Mpeak 22
CI6 60 103 11* 46 Unknown Mpeak 22
CI7 60 117 6* 57 Unknown F0F1F2 22
CI8 72 119 8* 47 Unknown F0F1F2 19
CI9 60 125 3* 65 Unknown Mpeak 20
CI10 36 152 8* 116 Unknown Mpeak 20
CI11 72 161 4* 89 Unknown Mpeak 20
CI12 24 154 15 130 Meningitis Mpeak 22
CI13 35 194 18* 158 Hereditary Mpeak 19
CI14 24 86 12 62 Meningitis Mpeak 22
CI15 36 79 14* 43 CMV Mpeak 22
CI16 36 98 11* 62 Meningitis Mpeak 22
CI17 48 106 16* 58 Unknown Mpeak 21
CI18 36 169 1* 133 Hereditary Mpeak 20
CI19 36 149 26 113 Meningitis Mpeak 20
CI20 36 86 9 50 Meningitis Mpeak 20
CI21 24 87 18* 63 Unknown Mpeak 22
CI22 48 117 9* 69 Unknown Mpeak 21
CI23 36 90 5* 54 Unknown Mpeak 22
CI24 48 99 14* 51 Unknown Mpeak 22
CI25 24 63 7* 39 Unknown Mpeak 22
Mean 43 9 yr 5 mo 12 70
SD 14 2 yr 7 mo 7 33
HA1 NA 136 6* NA Unknown
HA2 NA 114 9* NA Unknown
HA3 NA 97 9 NA Ototoxicity
HA4 NA 118 8* NA Unknown
HA5 NA 81 3* NA Hereditary
HA6 NA 81 6* NA Unknown
HA7 NA 84 8* NA Unknown
HA8 NA 129 6* NA Unknown
HA9 NA 149 9* NA Unknown
HA10 NA 171 16* NA Unknown
HA11 NA 167 3* NA Premature birth
HA12 NA 171 8* NA Meningitis
HA13 NA 171 6* NA Unknown
Mean 10 yr 2 mo 7
SD 2 yr 9 mo 3
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*

Suspected congenitel onset.

Children in the CI group ranged in age between 5 and 16 yr, and had a mean age of 9 yr 5 mo (SD = 2 yr 7 mo). They received their CIs between the ages of 31 mo and 16 yr, with a mean of 5 yr 7 mo (SD 2 yr 6 mo). Children in the HA group ranged in age between 6 and 14 yr, and had a mean age of 10 yr 2 md(SD = 2 yr 9 mo). There was not a statistically significant difference in age between the two groups [t(36) = −1.35, p = 0.184.]

Participants CI4, CI5, and CI8 used the F0F1F2 processing strategy, which is designed to present first formant information to the 5 most apical of the 22 electrodes, and second formant information to the remaining electrodes. Fundamental frequency information is conveyed by pulse rate duration during voiced segments of the signal and random intervals during unvoiced segments. The remaining children in the CI group used the MPeak processing strategy, which presents the same information as the FOF1F2 strategy, additional information about the third and fourth formants during voiced segments, and more high-frequency information during unvoiced segments. For a review of processing strategies, see Staller, Beiter, and Brimacombe (1994). One participant was stimulated on only 11 electrodes, and within 1 yr after this language sample was obtained, his device failed. He was subsequently explanted and then reimplanted.

All the children in the HA group were considered candidates for cochlear implantation on the basis of their audiological evaluations. They scored below chance on the following tests: Monosyllable, Trochee, Spondee test (Erber & Alencewicz, 1972), the Four-Choice Spondee test from the Early Speech Perception test battery (Geers & Moog, 1990), the Vowel Perception Test (Tyler, Fryauf-Bertshcy, & Kelsay, 1991), and the Phonetically Balanced Kindergarten Word Lists, (Haskins, Reference Note 1)(See Fryauf-Bertschy et al., 1997). Participants HA1-HA4 subsequently received CIs.

All children lived at home and attended a public school within their community or 60 miles thereof. One child in the CI group attended a state school for the deaf, but returned home each day. According to all parental reports, the children used simultaneous communication (Speech and Signed English) at home and in the school.

Speech and Language Testing

The speech production testing and the language sample were videotaped using a camcorder with audiovideo tracks. Phoneme production accuracy was assessed using a sentence repetition task consisting of 14 short and expanded sentences (e.g., “The girl runs.” and “The girl runs to catch the school bus.”). The examiner presented the sentences in both speech and sign, and the child repeated the sentence. Phonetic transcriptions of the sentences were compared with the target sentences to derive a percent phoneme correct score. This test was chosen because it provided a standardized sample from each child in that all children were given the same sentences to repeat.

A conversational language sample was collected using the protocol from the Systematic Analysis of Language Transcripts (SALT) manual(Miller & Chapman, 1993). The clinician had a 15 minute conversation with all the children. During this time at least one topic absent from time and space was introduced (e.g., “Tell me what you did over summer vacation.”). Typical topics discussed included pets, family, and school activities, and in some instances the child provided some narrative within the sample. All language samples were elicited by the first author, a fluent signer of Signed English with 14 yr of signing experience and extensive experience working with deaf children. Twelve minutes of each sample were transcribed by the first author and coded using SALT conventions. The words produced by voice and sign were transcribed, and the modes used to express each word and each bound morpheme was coded. The code [vs] indicated the word was produced with voice-and-sign, [s] indicated sign-only was used and [v] indicated voice-only was used. If the child signed “My dad work on a farm” but spoke “Dad works on a farm”, the message was transcribed as My[s] dad[vs] work/s[vs:root][v:end] on[vs] a[vs] farm[vs]. The child was given credit for use of a spoken word or morpheme if the vocalization was produced in the appropriate temporal sequence of a signed utterance.

Transcriber reliability was calculated on language samples from five children. The second transcriber was an educational interpreter who held an associate degree from an interpreter training program, an interpreter's license and a quality assurance Level 2 from the state of Wisconsin. Reliability was calculated on both the speech and sign transcription. The interpreter reviewed the transcriptions and noted any discrepancies. Mean intertranscriber item-by-item agreement was 0.96 Agreement regarding the specific occurrence of the bound morphemes was 0.98

General language measures extracted from the SALT analysis included total words used, type/token ratio, and unique words used. The bound morphemes coded in this analysis included plurals, possessives, third person singular, present progressive, and regular past tense. The child was given credit for an ending if it was judged to be vocalized, signed, or produced with both sign and voice, and the mode used was noted.

Omitted bound morphemes were coded. The obligatory context was defined as an instance where the ending would be required for the utterance to be grammatical, as in the following example: “When it is hard to say, she spell/*3s it out.” The third person singular tense is represented as 3s, and the * indicates it was omitted. There were instances where the structure of the sentence was ambiguous. In these cases an ending was not judged to be obligatory as in the example: “Then coach need sit down.”

Because the purpose of this study was to investigate use of inflectional morphemes in English, morpheme codes were not completed on words that included ASL sign markers, such as when a plural was indicated by repeating a sing. The ending was, however counted as obligatory. Six children used utterances that included elements and syntax unique to ASL. Utterances that were primarily ASL in nature were counted, transcribed, and marked with a code (ASL).

Speech Perception Testing

The 6-choice Word Intelligibility by Picture Identification Test (WIPI) by Ross and Lerman (1971) was administered live-voice in a quiet room. This test was performed in an audition-only condition. The children's familiarity with the vocabulary of the test was established before testing by asking the child to name, via voice or sign, each of the six words on the answer plate of the test before preceding with that test foil. All of the children could identify all of the vocabulary of the test before testing with the following exceptions: participant number CI16, who was not tested, and participants CI1 and CI25. These children were given a reduced set WIPI, which included 10 plates that contained words within their vocabulary.

The WIPI test was not administered to children in the HA group. They were unable to hear the stimuli.

Results

Information on use of communication mode and bound morphemes can be found in Tables 2 and 3, respectively. Speech production, perception and language data are presented in Table 4.

TABLE 2.

Mode of communication used to express whole words and bound morphemes.

Whole Words (% of total)
 Morpheme Endings (% of total)
Mode CI Group HA Group CI Group HA Group
Voice only 21 1 94 2
Sign only 9 31 5 94
Voice and sign 70 68 1 4
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CI = cochlear implant; HA = hearing aid.

TABLE 3.

Total number of bound morphemes used (by category) over total obligatory instances by individual participants in each group.

Participant Plural /s/ Possessive /s/ Present Progressive /ing/ Third Person Singular Past Tense /ed/ Total Used
CI1 1/1 0/1 5/6 3/8 0/1 9/16
CI2 9/11 1/1 1/1 1/1 4/4 16/18
CI3 2/5 1/4 2/2 2/3 1/9 8/23
CI4 0/4 0/0 0/0 0/3 0/1 0/8
CI5 4/5 5/5 5/6 1/1 1/6 15/23
CI6 5/10 0/2 0/0 1/1 0/3 6/16
CI7 5/11 1/3 0/0 2/5 0/4 8/23
CI8 27/27 9/9 3/3 12/12 8/8 59/59
CI9 2/3 1/1 7/7 0/0 1/4 11/15
CI10 12/12 5/5 13/13 4/4 10/10 44/44
CI11 24/24 1/1 10/10 14/15 5/7 54/57
CI12 13/15 1/1 1/1 2/2 0/1 17/20
CI13 16/16 0/1 1/1 5/11 2/2 24/31
CI14 2/2 0/0 3/3 1/1 0/0 6/6
CI15 24/25 4/4 6/6 6/6 0/0 40/41
CI16 0/2 0/0 0/0 0/0 0/0 0/0
CI17 2/3 0/2 0/0 0/1 0/2 2/8
CI18 2/4 0/0 0/1 0/0 0/1 2/6
CI19 0/6 0/0 0/0 0/1 0/4 0/11
CI20 1/1 0/1 3/5 1/1 1/4 6/12
CI21 0/3 0/0 0/1 0/3 0/2 0/9
CI22 16/17 1/3 1/1 1/3 0/3 19/27
CI23 3/5 0/1 1/1 0/2 0/1 4/10
CI24 12/16 6/7 9/9 1/2 1/3 29/37
CI25 0/3 2/2 19/20 1/1 0/3 22/29
Total 182/231 38/53 89/99 59/93 40/81 401/549
% 79 70 90 68 49 73
HA1 6/15 1/1 0/1 0/6 0/2 7/25
HA2 0/1 0/1 0/0 0/2 0/2 0/6
HA3 10/10 0/0 2/2 0/0 0/0 12/12
HA4 4/10 0/0 0/2 0/1 0/4 4/17
HA5 0/1 0/3 1/2 0/2 0/3 1/11
HA6 8/8 0/2 0/0 0/5 0/4 8/19
HA7 2/5 0/1 0/0 0/1 0/2 2/9
HA8 2/4 0/0 0/0 1/3 0/1 3/8
HA9 0/2 0/0 1/2 2/4 0/14 3/22
HA10 0/0 0/0 0/0 0/0 0/0 0/0
HA11 0/10 0/2 0/0 0/0 0/1 0/13
HA12 0/4 0/0 0/0 0/0 0/1 0/5
HA13 7/17 0/1 1/1 0/2 0/2 8/23
Total 39/66 1/11 5/11 3/29 0/40 48/170
% 59 9 45 10 0 28
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TABLE 4.

Perceptual, speech production, and language data for individual participants in the cochlear implant (CI) and the hearing aid (HA) groups.

Produced Correctly in a Short-Long Sentence Production Task (% Correct)
 Produced within a 12 minute Conversation Sample
Participant Number wipi* (% Correct) Phonemes Words MLU Total Words Unique Words Number of Utterances Total Bound Morphemes
CI1 65 44 8 3.95 281 115 75 9
CI2 40 42 11 6.68 598 217 97 16
CI3 80 72 41 6.74 475 86 79 8
CI4 26 46 14 3.98 210 98 59 0
CI5 72 65 35 4.91 302 138 66 15
CI6 48 57 24 5.42 346 154 68 6
CI7 36 38 19 4.58 296 126 69 8
CI8 80 93 70 8.96 675 232 88 59
CI9 56 54 16 4.88 417 186 89 11
CI10 80 80 43 8.32 530 208 74 44
CI11 56 75 46 8.11 929 289 126 54
CI12 36 45 16 7.92 466 183 62 17
CI13 70 67 30 8.32 676 237 88 24
CI14 44 49 16 5.18 139 68 70 6
CI15 86 79 49 6.07 446 169 84 40
CI16 — 17 3 3.16 262 110 87 0
CI17 38 36 11 3.92 202 95 59 2
CI18 46 37 11 5.23 311 146 63 2
CI19 16 27 3 5.73 556 229 99 0
CI20 44 50 24 7.26 188 82 47 6
CI21 36 31 6 2.55 191 111 76 0
CI22 94 76 46 5.08 281 127 61 19
CI23 72 53 16 2.99 211 112 75 4
CI24 86 69 38 4.69 473 186 109 29
CI25 96 54 14 3.40 315 100 101 22
HA1 NA 54 19 6.0 345 155 60 7
HA2 NA 30 5 2.70 108 67 42 0
HA3 NA 19 0 2.07 108 77 63 12
HA4 NA 55 46 4.34 210 135 73 4
HA5 NA 43 5 4.27 264 142 63 1
HA6 NA 20 0 2.25 152 86 75 8
HA7 NA 40 19 3.41 216 119 66 2
HA8 NA 35 0 3.43 192 121 56 3
HA9 NA 34 3 4.71 387 205 85 3
HA10 NA 66 41 2.94 106 78 36 0
HA11 NA 60 13 4.72 307 156 65 0
HA12 NA 59 30 7.40 444 184 61 0
HA13 NA 78 46 4.64 261 147 58 0
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*

Percent correct on the Word Intelligibility by Picture Identification Test.

Communication Mode

The number of total words produced via voice-and-sign mode, voice-only mode, and sign-only mode was tallied and divided by the total number of words produced. The percent of words produced via each modality was calculated (Table 2). Voice-and-sign mode was used to express whole words within conversations a majority of the time for both the CI group and the HA group. For the CI group voice-only mode was the next most frequently used mode, but for the HA group, sign-only mode was the next most popular mode.

The total number of word endings produced via voice-and-sign mode, voice-only mode, and sign-only mode was tallied and divided by the total number of word endings produced. These results also appear in Table 2. This analysis revealed differences between the two groups, and was also in contrast with the whole word data. The CI participants most often used voice-only mode. In contrast, the HA participants tended to use sign-only mode to mark endings. Neither group tended to use voice-and-sign mode.

Use of Bound Morphemes

We next analyzed use of bound morphemes, independent of communication mode. Analysis of the 12 minute conversation samples revealed that the total number of morphemes used by individual members of the CI group ranged from 0 to 59, with a mean of 16 (SD = 17). Totals for the HA group ranged from 0 to 12, with a mean of 3 (SD = 1). The difference in the use of bound morphemes between groups was statistically significant [t(36) = 2.56, p = 0.015]. Table 3 lists the morpheme endings used; the numerator indicates the number of endings produced by each participant, and the denominator indicates the number of obligatory contexts possible. The number of tokens of each morpheme used by each group was computed. The two groups were similar in their frequency patterns, using plural morphemes most often, followed by present progressives, possessives, third person singular forms, and regular past tense forms. The CI group used the present progressive tense (-ing) most consistently in the obligatory context (90% of the time). They used the past tense (-ed) in the obligatory context with the least consistency (49% of the time). The HA group used the plural (−s) in the obligatory context most consistently (56% of the time), but no one in the HA group used the past tense (-ed) form.

Bound Morpheme use and Speech Perception

Pearson correlations were performed between each CI participants' scores on the WIPI and the total number of bound morphemes they used. Table 4 lists raw scores. Because of the number of correlations performed a hypothesis-wide alpha level of 0.01 was adopted as the level of significance. For readers who wish to apply a more conservative approach, the absolute probability levels for all correlations are given. The analyses revealed a significant relationship between WIPI scores and total bound morphemes used (r = 0.574, p = 0.003). These results indicate that there was a tendency for children who scored better on the WIPI to include more English inflected endings within conversation.

Bound Morpheme Use and Speech Production Skills

The relationship between accuracy of phoneme production and ending use was investigated within the CI group and the HA group. The accuracy of phoneme production was correlated with the use of inflected endings only for the CI group.

First we will consider the CI group. Correlations between the percent of phonemes produced correctly in the imitative sentence task and the number of endings produced within the conversation task were as follows: Plurals(r = 0.750, p = 0.0001); possessives (r= 0.688, p = 0.0001); third person singular (r = 0.662, p = 0.0001), and regular past tense (r = 0.574, p = 0.003). Use of present progressive was the only ending that did not show a significant relationship with phoneme production. The combined use of all five morpheme endings was also significantly related to accuracy of phoneme production (r = 0.815, p = 0.0001).

The relationship between use of endings and phoneme accuracy for the HA group was not statistically significant.

Speech and Language Results and Experience with a CI

Pearson correlations revealed relationships were significant between CI experience and use of third person singular tense (r = 0.550, and p = 0.003). Length of experience with a CI was correlated with accuracy of words produced correctly on the imitative sentence task(r = 0.568, p = 0.004). The relationship between age at testing, phoneme accuracy, use of plurals, possessives, present progressives, third person singular or regular past was not statistically significant.

To determine whether age at testing was a confounding variable in determining the relationship between phoneme production, use of bound morphemes, and months of CI experience, a partial correlation was completed with age at testing partialed out. The correlations were significant for phoneme production and length of experience with a CI (r =0.836, p = 0.0001) and for total bound morphemes used and length of experience (r = 0.437, p = 0.0001).

Discussion

Children with prolonged experience with CIs used inflected endings conversationally significantly more often than a group of similarly aged children with profound hearing loss who use HAs. In this study both CI and HA users marked plurals most commonly, followed by present progressives, possessives, third person singular, and regular past tense. Thus, they appear to have a similar progression in their mastery of endings, but differ primarily in their skill levels.

A previous investigation by Tye-Murray, Spencer, and Woodworth (1995) revealed that during a story retell task, children who used simultaneous communication tended to use voice-and-sign mode 83% of the time, voice-only mode 9% of the time, and sign-only mode 7% of the time. In the present investigation, which used open-ended conversation, this trend was replicated for both the CI group and the HA group. The primary mode of communication used to express a majority of words within conversation for both HA users and CI users was voice-and-sign. In contrast, the mode used to express bound morphemes for CI users was usually voice-only. When HA users produced bound morphemes, they used sign-only modality.

The use of voice-only mode to express English endings by CI users is significant because these morphemes are marked acoustically by mid- and high-frequency information in the speech signal. It suggests the following process: first, the CI offers them acoustic access to the sounds; second, as the CI users begin to perceive these sounds they incorporate them into their phonology; and finally, the sounds are expressed in their spoken morphology.

Two caveats to the above explanation must be appended. First, this study did not assess competence in grammatical morphology for either group. That is, no testing was completed to determine how well the children understood when a morpheme should or should not be included in a specific context. It is possible that the CI children have increased accuracy in production of all phonemes in general as a result of CI experience and thus, are better able to speak endings. Improvements in phonologic repertoire may give these children a means of marking a previously gained competence in morphology. A second caveat is that there were some participants who did not use endings, or due to the nature of their productive language structure it was not possible to derive which ending would have been obligatory. In these cases it was not possible to assess the child's knowledge of an ending.

Use of inflected endings was not related to the age of the participants in either the CI group or the HA group. This finding replicates the data of Schick and Moeller (1992), who examined inflected endings in profoundly deaf children of a similar age group. In the current study, bound-morpheme use was related to the length of experience that a child had with a CI and speech perception. These findings suggest that use of English inflected endings may be less affected by mutation and aging, and more affected by auditory inputs available via the CI. We speculate that once the children in this study acquired a stable vocabulary base through sign and listening, they may have then extracted the significance of bound morphemes, perhaps through listening, and generalized their use to many contexts.

This scenario corresponds with several models of language acquisition described for children with normal hearing (Bloomfield, 1933; Connell, 1989; Swisher & Snow, 1994). It may be that once a child has reached an understanding of a word meaning and the relationship that a bound morpheme has to the word, the child can develop production skills to mark the morpheme. Given that there is a relationship between accuracy of phoneme production and production of morphemes, it also possible that children must first incorporate the sound associated with bound morphemes, namely/ s, z, t, ng/, into their phonology before they demonstrate their linguistic knowledge via the production mode. Further longitudinal data regarding children's phonological development after implantation may reveal the exact nature of this relationship.

More research is needed to understand how information provided from the CI influences the user's ability to code verbal information during everyday listening. For instance it would be beneficial to know whether CI users tend to use of phonologically based or a sign-based coding strategy (e.g., Bellugi & Fisher, 1972; Lichtenstein, 1985). In the present study children with CI experience used the voice-and-sign mode to communicate a word but relied on the voice-only mode to communicate the morpheme ending. This findings suggests that the sound cue is an important part of their coding process even when they use a sign-based coding strategy. The use of a phonological template as a building block for language acquisition may ultimately enable children who use CIs to develop a better representation of English grammar than children who use HAs.

Acknowledgments

This study was supported (in part) by a research grant awarded to the Department of Otolaryngology-Head and Neck Surgery, University of Iowa(number 2 P50 DC 00242 from the National Institutes of Deafness and Other Communication Disorders, National Institutes of Health grant RR00059 from the General Clinical Research Centers Program, Division of Research Resources, NIH, the Lions Clubs International Foundation, and the Iowa Lions Foundation. The audiological data reported in this investigation were collected by Holly Fryauf-Bertschy in a protocol supervised by Richard S. Tyler.

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