The Phonological Systems of Deaf Children

THE

PHONOLOGICAL

SYSTEMS

OF

DEAF

CHILDREN

Barbara Dodd Medical Research Council, London, England

Samples of a group of deaf children's spontaneous speech were used to derive phonological rules. The predictive value of some of the rules was assessed by asking another group of deaf children to lip-read and read nonsense words. The results indicated that the phonological systems of profoundly deaf children are partially rule-governed. There was also some evidence which suggested that lipreading was a major input to the deaf children's phonological systems.

T h e phonology of the deaf is usually described in terms of its deviation from normal phonological systems. Lenneberg (1967) found differences in prelinguistic utterances between normal and deaf children after six months of age. Silverman (1963) surveyed the literature and concluded that deaf speech was characterized by arhythmia, excessive nasality, neutral and prolonged vowels, superfluous syllables between abutting pairs, few pitch changes, lack of distinction between voiced a n d voiceless pairs, malarticulation, and the omission of consonant clusters, consonants, diphthongs, and vowels. A different approach to the phonology of the deaf has been suggested by West and Weber (1973) in their presentation of a linguistic analysis of the phonological system of a hard-of-hearing four-year-old child with 58-dB airconduction loss in the better ear. Analysis to determine what her speech did express revealed that the child's phonology contained r u d i m e n t a r y patterns of linguistic development such as the elongation of vowels to designate final consonants and the use of phonemic contrast. Oller and Kelly (1974) studied a hard-of-hearing child who suffered an average 60-dB loss in both ears and found that she produced errors similar to those of young hearing children. If signs of a structured phonological system can be found in a young partially hearing child, it may be possible that the profoundly congenitally deaf also acquire some consistent phonological behavior. T h e purpose of the first experiment was to test this possibility. T h e second experiment was designed to assess the predictive value of any rules derived from the first study and to investigate the effect of two different inputs, reading and lipreading, on these rules. 185

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186 JOURNAL OF SPEECH AND HEARING DISORDERS

EXPERIMENT

XLI 185-198 1976

1 METHOD

Subjects

T e n profoundly congenitally deaf children acted as subjects. Eight of the subjects had a mean pure-tone average loss for the better ear for frequency range 0.5, 1, and 2 kHz of 102.2 sound pressure in dB, SD 11.09 dB, re ISO norms. Two of the subjects had mean thresholds which exceeded 120 dB. Known causes of their deafness were found in school medical records and included maternal rubella, thalidomide poisoning, sickle-cell anemia, and familial deafness. T h e subjects' mean chronological age was 11 years zero months, range nine years five months to 12 years four months. There were six males and four females. All subjects attended a junior school for the deaf in inner London. School policy encouraged the use of spoken language in the classroom, and children were encouraged to learn to lip-read. Procedure

Forty-five colored pictures of familiar objects and animals on 4" x 4" flash cards were presented to each subject in random order. T h e children were asked to name the pictures. T h e procedure was repeated to gain two examples of articulation for each name. Testing was carried out in a quiet room in the school building. T h e procedure was tape-recorded on a Uher Royal Stereophonic tape recorder. Transcription of Utterances

Two speech pathologists made phonetic transcriptions of all recorded utterances made by each subject. T h e transcriptions were concerned only with consonants and the semivowels ]j/ and ]w/; vowels were not considered. Appendix A contains phonetic transcription of those deviant utterances which were acceptable for analysis because they were produced consistently by a subject on both naming trials and also transcribed identically by both speech pathologists. Correct productions are not listed in Appendix A, and only one example of each deviant form is given though many replications occurred. Since the aim of the experiment was to find consistent phonological behavior, it was necessary to disregard those utterances which gave rise to differences between the two transcriptions, and also to those utterances not produced identically by each subject on both the naming trials. However, less than 15% of the utterances had to be disregarded for these reasons. RESULTS

Repertoire of Phonological Units. Phones which were not produced by subjects are shown in Table 1. All other of the 24 English consonant phones


DODD: PhonologicalSystems 187 were used either appropriately or inappropriately by the subjects. All subjects exhibited more than half the complete phone repertoire of English. TABLE 1. English consonant phones not produced by subjects.

Subject

Number o/Phonemes Not Used

1 2 3 4 5 6

2 3 1 5 4 5

7

9 11

8 9 10

1 4 Mean 4.5

Phones Not Used / / /~/ /rj /~ / /~ /~ /~/ /~ Totals 7

0 5/ 015i/ 0 15 tl 0 15 j/ 0 15 i/ tl j tl i tl 0 15 il 6 6 6

4

d3/ d~/ d~ I ~ h s z/ d~ f 5 h t d k g/ 4

2

2

2

1

1

1

1

1

1

Phonological Rules A set of phonological rules was derived for each subject which accounted for all errors made by that subject. Those rules held in common by two or more of the subjects are shown in Table 2. There were 13 examples where one subject produced an error type consistently that no other subject made; these are not included in the table. Table 2 shows the number of subjects producing errors on listed phonological features, those features being organized in terms of the functions: cluster reduction, consonant harmony, and simplification of the sound system. 1 Table 2 also shows the number of subjects using each phonological rule. T h e table does not fully describe phonological systems used. T h e purpose of the analysis was to describe phonological rules commonly held by the group of subjects. It should be noted that some subjects occasionally used different rules in dealing with a particular consonant cluster; for example, one subject reduced nasal plus consonant clusters by deleting the nasal in hand [h~ed], but the nonnasal consonant in orange [orm]. In this sense the rules were optional.

Morpheme Structure There were two morpheme structure conditions that deaf subjects imposed. All 10 subjects reduced multisyllable words by deleting unstressed, initial syllables ([nanA] for banana, [matov] for tomato); six of the subjects interpolated vowels, or consonants to obtain C V C V forms ([f~lavb] for flower, [hremol] for hammer). 1For discussion of the functions see Smith (1973).


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1976

TABLE 2. Phonological rules.

Rule Function and Phonological Configuration

Number ol Subjects in Error on Phonological Configuration

Cluster Reduction Nasal plus consonant

10

Example

[ha~d] hand [orIn] orange

Phonological Rules A 1l Rules Optional

Nasal deletes before consonant

8

Consonant deletes after nasal

2

Total deletion of consonant cluster

6

/s/deletes preconsonantally /t, k/delete after/s/finally and medially

10

[fI:a] finger /s/plus

consonant

10

[pun] spoon

[povs] post [bI:It] biscuit

/1, r, w/

/1/plus consonant

3

/k, g/delete before/1, r, w /

9

/I/deletes after/k, g/

2

/1/deletes before/d, k/

S

milk [bid3] bridge [rain] train


8

/r, 1/delete after/b, p, t, d/

8

/d, t, f/delete before/r, 1/

4

[kekal] kettle

Velarization o f / t / b e f o r e syllabic/1/

[dei1] nail [bays] mouse [trei] train [sklpln] skipping

/ n / i s substituted for by [d] initially

7

/ m / i s substituted for by [b]

10

/n/deletes finally

10

[sovda] soldier

[ma] /b, p, f, t, d/ plus/I, r~

Consonant Harmony / t / Before Syllabic/1/ Systemic Simplification Nasals

/11/ Initially

Nonsonorant consonants

3

10

4


[Iok] clock [gas] glass

/ k , t, g / p l u s

Number o/ Subjects Using Each Rule

[amd] hand [fl] /ish [d~em] am

[ks] f~sh [brIsl bridge

/ 0 / i s substituted for by [n]

8

/h/deletes initially

7

/J', ds, tJ'/deletes finally /ds, t[, 0, ~5, S/are substituted for by [d] /f, ds, t[/are substituted for by [s] and [z]

7

/ d 3 / i s substituted for by [3]

6


4

DODD: Phonological Systems 189

TABLE2. Phonological rules. (Continued)

Rule Function and Phonological Configuration

/g, k /

Number oI Subiects in Error on Phonological Configuration

9

Example

[d31] girl

[klo] clock

[31] girl

/1/

4

/ s / after /n[

9

[pantol]

/s/and/z/

9

[mavt]

pencil mouse

[hav] house

[3ebra]

zebra

/r/

$

[twem]

/ t / /d/

5

[bIskI]

/f/ /v/

6

[plav:~]

train biscuit flotver

Oil

4

/g, k/are substituted for by [d, t]

7

/g, k/delete finally

7

/g, k/deletes initially

2

/1/deletes finally /s/is substituted for by [t] after/n/ /s/ and /z/ are substituted for by It, d]

2 9

/s, z/delete finally

7

/z/is substituted for by [3]

2

[g3] girl

syllabic/1/

Phonological Rules All Rules Optional

Number o] Subjects Using Each Rule

lea! [,p~nsu] pencil

$

/ r / i s substituted for by [w] /t/deletes finally

5

/f, v/are substituted for by [p, b]

4:

/f/deletes finally

2

syllabic/1/vocalizes to [u]

4

DISCUSSION

T h e results demonstrate that hearing is not essential for the acquisition of an extensive phone repertoire or for the development of an at least partially rule-governed phonological system. While the results do not represent a total description of either the phone repertoires of the subjects or their phonological systems, they do show that the deaf subjects used some phonological rules consistently, both individually, and as a group. Only two subjects exhibited any real paucity of phones, one having acquired 13, and the other 15 of the possible 24 English consonant phones. T h e other eight subjects' repertoires were almost complete, and those sounds missing are often acquired late by hearing children (Reese and Lipsitt, 1970). Another similarity between the phonology of the deaf and young hearing


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children is that all the rules used by the deaf subjects also appear in the rule systems of hearing children at some time (Dodd, 1974). There are two major hypotheses which could explain the consistent rulegoverned nature of the deaf subjects' phonological systems. T h e deaf could be internalizing an incomplete acoustic trace through speech teaching using residual hearing (Fry, 1966) and mapping their vocal output from this information in much the same way as normal children. This explanation would predict less homogeneity in the error pattern than has been found in this experiment. There appears to be no pattern in the phone repertoires which would indicate that those phones produced, or not produced, belonged to particular frequency bands. A more likely explanation is that the deaf children were internalizing a lipread trace for words and using this visual input as the primary source of information from which to map their vocal output. One indication that this may be the process deaf subjects were using was their treatment of / k / and / g / . These sounds are difficult to lip-read being produced by raising the back of the tongue to touch the soft palate. They may be deleted in clusters and in final position simply because they are difficult to see in those environments. This may also explain the absence of /13/ from seven of the subjects' phone repertoires. In order to validate the findings of this experiment and to investigate the role of lipreading as an input to phonological systems another experiment was carried out to test the hypotheses: l. That rules frequently used by the deaf subjects in Experiment 1 are predictive of other deaf childrens' phonological systems. 2. That different types of input, such as reading the written word and lipreading, will affect phonological output, because those sounds which are difficult to lip-read will be produced differently according to input.

EXPERIMENT

2 METHOD

Subjects Eight profoundly, prelinguistically deaf children, and two severely deaf children acted as subjects. T h e m e a n pure-tone average loss for the better ear for frequency range 0.5, 1, and 2 kHz for seven of the profoundly deaf subjects was 96.25 dB, SD 15.2, re ISO norms: the other profoundly deaf subject had a mean threshold that exceeded 120 dB. T h e two severely deaf subjects had a mean pure-tone loss of 65.83 dB. Those causes of the subjects' deafness that were k n o w n were obtained from school medical records and included maternal rubella, meningitis at 10 months, and familial deafness. T h e subjects' mean chronological age was 14 years 11 months; range 12 years nine months to 16 years 11 months. Older subjects were necessary for this experiment because subjects had to be able to read well. All subjects attended a senior school


DODD: PhonologicalSystems 191 for the deaf in inner London. School policy encouraged the use of spoken language, and children were expected to be able to lip-read.

Procedure Thirty-six nonsense words were designed to test nine of the rules used consistently by seven or more children in Experiment 1. T h e rules are listed in T a b l e 3, and the nonsense words are in Appendix B. T h e nonsense words TABLE3. Phonological errors made on nonsense words.

Rule

1. 2, 3. 4. 5. 6. 7. 8. 9.

Reading Number of Other Examples Rule Correct Errors

nasals delete before consonants / s / deletes preconsonantally /k, g/delete before/1, r, w/ /1, r/ delete after/p, b/ / n / i s substituted for by [d] initially /m/ is substituted for by [b] /k, g/ are substituted for by [t, d] /k, g/delete finally /n/ deletes finally

Lipreading Other

Rule Correct Errors

40 30 50 40

22 25 8 18

8 2 13 18

10 3 29 4

20 21 19 22

9 $ 15 18

11 6 16 0

20 70 60 70 30

4 41 7 29 7

9 26 41 25 16

7 $ 12 16 7

5 42 3 51 16

7 25 30 9 8

8 $ 27 10 fi

consisted of 18 C V C words, 10 C C V C words, three C V C C words, two C V C V C words, one C V C C V C C word, one C V C C V word, one C V C C F C word. Five subjects were asked to read the words aloud from printed cards and then to reproduce the same word after lipreading the examiner's production. T h e other five subjects were asked to lip-read first and reproduce the words and then to read them aloud from the printed cards. Subjects were told that the words were nonsense words. T h e procedure was tape-recorded on a Uher Royal Stereophonic tape recorder, and testing was carried out in a quiet room in the school building.

Transcription of Utterances T w o speech pathologists made phonetic transcriptions of all the recorded utterances made by each subject. T h e transcriptions were concerned only with consonants and consonant-vowels; vowels were not considered. Since the design of this experiment necessitated that data be obtained for all stimuli, any inconsistencies which occurred between the two transcriptions had to be res o l v e d by listening to the appropriate utterances again. However, it was not possible to make a reliable transcription of eight of the utterances, and for statistical purposes these utterances were classed as "other errors." "Other errors" also include errors made in the production of phonological configurations which were not in accordance with the phonological rules tested.


192 JOURNAL OF SPEECH AND HEARING DISORDERS

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RESULTS Predictive Value of Rules

T a b l e 3 lists the nine rules tested and shows the expected frequency of rule usage, actual frequency of rule usage, correct productions, and "other errors" for reading and lipreading conditions. T a b l e 4 shows the results of related t tests comparing rule use against the TABLE

4. Related t ratios for rule usage versus other errors.

Rule

1. 2. 3. 4. 5. 6. 7. 8. 9.

t

Reading Significance

nasals delete before consonants 2.25 < /s/deletes preconsonantally 3.99 < /k, g/ delete before/1, r, w/ 3.84 < /1, r/ delete after/p, b/ 2.26 < / n / i s substituted for by [d] initially 0.82 / m / is substituted for by [b] 5.12 < /k, g/ are substituted for by [t, d] 0.83 /k, g/ delete finally 2.33 < / n / deletes finally Means Equal

t

Lipreading Significance

0.05 0.01 0.01 0.05

2.39 2.50 0A5 6.14

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