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Phonological Process development with MLU-referenced guidelines
JOURNAL
OF COMMUNICATION
DISORDERS
395
15 (1982), 395-410
PHONOLOGICAL PROCESS MLU-REFERENCED
DEVELOPMENT GUIDELINES
WITH
REX JOE PRATER The Universiry of North Carolina at Greensboro
ROGER Rockingham
WILLIAMS
SWIFT
County Enrichment
Center
Sixty subjects between the ages of 2 1 and 48 months were placed into groups based on mean length of utterance (MLU) and chronological age (CA) to test Stampe’s hypothesis about the development of phonological processes. The subjects were given the Phonological Process Analysis (Weiner, 1979). and a proportion score for each of sixteen phonological processes was derived for each subject. The use of the various phonological processes across MLU groups and age groups was analyzed by multiple regression correlation, three-way ANOVA, and Tukey’s HSD tests. MLU was found to be the best classification for the subjects for describing the phonological processes. The results and discussions present MLU-referenced guidelines regarding the emergence, duration, elimination, and universalitv of the sixteen ohonoloeical orocesses.
Introduction
Stampe (1969) suggests that in attempting to produce adult words, children reduce them to simpler patterns through an innate system of phonological processes. According to this hypothesis, phonological acquisition is seen as the suppression and elimination of these simplifying tendencies. The purpose of this study was to examine Stampe’s hypothesis using MLU and chronological age for classifying the subjects and the Phonological Process Analysis (Weiner, 1979) to obtain measures. The use of chronological age for describing phonological acquisition has had considerable historical precedent (Poole, 1934; Prather et al., 1975; Templin, 1957; Wellman et al., 1931). The use of MLU for analysis of phonological acquisition was in keeping with the research findings of Menyuk and Looney ( 1972), Schwartz and Folger (1977), Shriner et al., (1969), and Whitacre et al. (1970). who have suggested a complex interaction between various aspects of linguistic acquisition, including phonology. Several studies (Ingram, 1974; Kornfeld, 1971; Menn, 1971; Moskowitz, 1970; Smith, 1973; Waterson, 1971) have attempted to use phonological analysis
Address correspondence
to Rex J. Prater, Ph.D.,
D Elsevier Science Publishing Company, Inc., 52 Vanderbilt Ave., New York, NY 10017
3 Amberhill
Court, Greensboro,
NC 27405.
1982 0021-9924/82/050395-16$02.75
396
R. J. PRATER
and R. W. SWIFT
to describe the speech of normal children. Likewise, the utility of using phonological analysis in case studies of children with articulation disorders has been demonstrated (Bodine, 1974; Haas, 1963; Lorentz, 1974; Oiler and Kelly. 1974; West and Weber. 1973). Even though phonological milestones have not been fully determined, attempts at using phonological analysis for purposes of therapeutic intervention have been made (Compton, 1970. 1975; Cracker, 1969; McReynolds and Bennet. 1972; McReynolds and Huston, 197 I; Oller, 1973; Pollock and Rees. 1972). Knowledge about normal phonological development in children is far from complete. If Stampe’s natural phonology theory is correct, there is a need to know more about the emergence, duration, elimination, and universality of each of the phonological processes. The developmental relationship between these processes is presently undefined. Method Subjects
The subjects in the study were 60 children ranging in age from 21 to 48 mo. To be accepted as a subject for this study, each child must have been reared since birth in a home where English was spoken as the first language and must not appear to have any hearing defects or neurological problems as observed by the examiners. Stimulus Materials and Prowdurc~s
The Phonological Process Analysis (Weiner, 1979) was administered to each subject. This test consists of 142 line drawings of objects and actions that the subjects named after an indirect verbal model was presented by the examiner (e.g., Uncle Fred is wearing a hat. What is Uncle Fred wearing?). The picture stimuli of the Phonological Process Analysis are grouped into subtests designed to elicit one of 16 phonological processes. Twelve of the process subtests have 8 stimulus items, three have 6 items, and one subtest has 28 items. The process subtests are grouped under three major categorical headings: (1) Syllable Structure Processes, which includes the subtests of deletion of final consonants, cluster reduction, weak syllable deletion, and glottal replacement; (2) Harmony Processes, which includes labial, alveolar and velar assimilation, prevocalic voicing. and final consonant devoicing; and (3) Substitution Processes with the subtests of stopping, gliding of fricatives, affrication. fronting, denasalization, gliding of liquids, and vocalization.
PHONOLOGICAL
PROCESS
DEVELOPMENT
391
Score Derivation The verbal responses of each subject to the picture stimuli of the Phonological Process Analysis were phonetically transcribed on a score sheet immediately following each response. The verbal responses were recorded on audiotape for later verification of transcription accuracy. An item-by-item analysis of interjudge reliability for fifteen subjects ’ total responses was 91%. Intra-judge reliabilities for scoring three subjects’ total responses after a seven-day interval were 94% and 95% for the two examiners. Subjects’ scores for each process on the Phonological Process Analysis were derived as a percentage of the number of times the subject demonstrated the process to the total number of times the process was specifically tested in any one subtest. Results For purpose of analysis, the subjects were grouped by MLU and by chronological age (CA). There were six equal MLU groups with each group having a range of one morpheme. Total range for all MLU groups was 1.00 to 6.99 morphemes. MLU was calculated according to the method of Brown (1973). Seven age groups were also used for classifying the subjects. Each age group had a range of 4 mo and the total range for all age groups was 2 1 to 48 mo. Mean age and MLU for the groups are presented in Table 1.
TABLE I Mean Age and Mean MLU for Groupings
Grouping Age Age Age Age Age Age Age MLU MLU MLU MLU MLU MLU
Group Group Group Group Group Group Group Group Group Group Group Group Group
N
Mean Age in Months
Used in the Data Analysis
Mean MLU
SD
-
1.94 3.29 3.51 4.88 5.56 6.55 5.89
I .09 1.27 1.26 I .64 0.50 0.00 0.10
5.23 2.70 3.85 4.04 6.55 4.13
-
-
SD
I
10
-
2 3 4 5 6 7
10 16 12 7 2 3
-
1 2 3 4 5 6
10 10 10 10 10 IO
24.9 27.1 30.5 30.5 37.6 37.5
R. J. PRATER
398
Edunting
thr Rdatiw
Strc~ngth.r
anti R. W. SWIFT
of MLU
trtd CA jot- Description
Purposes To evaluate whether MLU or CA was a better measure for describing the development of the phonological processes. a hierarchical multiple regression correlation of the subjects’ scores for each phonological process with age groups and MLU groups was performed. In a hierarchical multiple regression correlation, the variables that have higher inclusion level values are brought into the equation before variables with lower inclusion values. By examining whether age groups or MLU groups were drawn into the regression analysis more frequently as the higher inclusion level variable and by examining the change in the squared ip value when the second variable was included, an evaluation of the relative strengths processes
of age grouping and MLU was accomplished.
grouping
for describing
the phonological
For the ten phonological processes that were significantly (p < 0.01) related to either age or MLU groups, MLU group was the higher inclusion-level variable drawn into the regression analysis for seven phonological processes, and age group was the higher variable was drawn into the regression
for just three processes (Table 2). When age group as the lower inclusion-level variable, the change in
the squared r values was never more than 1%. To exarnine further whether MLU grouping or age grouping better described use of the phonological processes. an average score for each subject for each of three major categorical headings (Syllable Structure Processes. Harmony Processes, and Substitution Processes) was computed by calculating the mean of all subtest scores for each subject under each major categorical heading. A three-way analysis of variance was performed to determine whether the average score for each of three major process categories across age groups and MLU groups was different. Significant main effects
for the three major categories
(F = 43.418; d! = 2,54;p = 0.000) = 0.000) were found. No significant 5,54; p 1 0.05) was demonstrated.
of phonological
process
and MLU groups (F = 11.018; cif = 5,54; p main effect of age groups (F = 1.687; elf = In addition, a significant MLU group x
Major Process Category two-way interaction (F = 6.632; df = 10,54; p = 0.000) revealed that differences in subjects’ scores occurred on the basis of an interaction among varying levels of MLU grouping and the major process categories. Therefore, because MLU group was drawn into the multiple regression correlation equation rnore frequently as the higher inclusion-level variable and because the regression data and the three-way analysis of variance data were in agreement, MLU grouping was chosen as the more accurate classification method for describing processes.
the development
of the majority
of the phonological
PHONOLOGICAL
PROCESS
399
DEVELOPMENT
TABLE 2 Sample Regression Coefficients (b), Multiple Correlation (R), and R* for Regression of Proportion Scores for the IO Phonological Processes that Were Significantly @ < 0.05) Related to Age Groups and/or MLU Groups (Xl R
R2
-0. I1 -
-0.60 -0.59
0.36 0.35
-0.47 -0.71
-0.36
-0.76 -0.71
0.57 0.50
Age
-0.67 -0.70
-0.42
-0.70 -0.70
0.49 0.49
Age MLU
MLU
-0.31 -0.37
-0.09 -
-0.38 -0.37
0.14 0.14
Velar assimilation
MLU Age
Age
-0.39 -0.47
-0.12 -
-0.47 -0.47
0.23 0.22
Prevocalic
MLU Age
Age
-0.42 -0.44
-0.03
-0.44 -0.44
0.19 0.19
Ane
’
-0.58
-0.58
0.34
Stopping
MLU Age
Age
-0.38 -0.49
-0.17 -
-0.51 -0.49
0.26 0.24
Fronting
MLU Age
Age
-0.30 -0.40
-0.16
-0.42 -0.40
0.18 0.16
Vocalization
Age MLU
MLU
-0.51 -0.56
-0.07
-0.56 -0.56
0.32 0.31
Phonological
Process
X/
x2
b,
MLU Age
Age
-0.66 -0.59
MLU Age
Age
MLU Age
Alveolar assimilation
Deletion of final consonants
Cluster reduction
Weak syllable deletion
voicing
Final consonant devoicing
‘F-level
or tolerance
level insufficient
Effects of Increased
for computation
MLU on Process
4
of second variable.
Usage
To examine the effects of increased MLU on subjects’ scores for each phonological process, a statistical analysis of variance for each process was performed. Significant differences (p < 0.05) were found among MLU groups for all but five processes--glottal replacement, alveolar assimilation, gliding of fricatives, affrication, and denasalization (Table 3). The MLU group data for each phonological process were analyzed using Tukey’s “honestly significant difference” test. This analysis was used to determine homogenous subsets of the MLU groups with regard to each process, and to determine between which pairs of MLU groups significant differences (p
400
R. J. PRATER
and R. W. SWIFT
TABLE Means
and Standard
Deviation
for the MLU
3
Groups.” M LU Groups
I
Variable Svllable
Structure
Deletion
3
4
5
6
0.90
0.62
0.32
0.23
0.08
0.07
p = 0.000
0.08
0.27
0.31
0.29
0.09
0.07
llf = s.54
0.87
0.80
0.63
0.58
0.28
0.17
17 = 0.000
0.09
0.12
0.22
0.28
0.27
0.15
df = 5,54
0.83
0.80
0.63
0.50
0.35
0.18
p = 0.000
0.14
0.07
0.21
0.21
0.24
0.15
c/f = 5.54
0.09
0.15
0.09
0.03
0.15
0.04
0.13
0.21
0. IO
0.08
0.31
0.08
(If =
0.28
0.39
0.28
0.38
0.28
0.1 I
p < 0.038
0.18
0.17
0.20
0.22
0.23
0.16
q
Processes
of final
23.455
consonants
Mean SD Cluster
F
2
19.21 I
reduction
Mean SD Weak syllable Mean SD Glottal
20.709
deletion
replacement
Mean SD Harmonv
0.9.52 p > 0.05 5.54
Processes
Labial
2.551
assimilation
Mean SD Alveolar
= 5.54 0.881
assimilation
Mean
0.25
0.18
0.13
0.17
0.13
0.11
p < 0.05
SD
0.21
0.18
0.17
0.18
0.15
0.10
0.29
0. I6
0.09
0.06
0.09
0.01
p = 0.000
0.18
0.12
0.08
0.07
0.13
0.04
df =
Velar
7.381
assimilation
Mean SD Prevocalic Mean SD Final
consonant
5.54
3.990
voicing 0.26
0.26
0.08
0.01
0.03
0.05
p < 0.004
0.27
0.34
0.1 I
0.04
0.05
0.07
df =
5.54
9.545
devoicing
Mean
0.08
0.66
0.51
0.59
0.14
0.13
p = 0.000
SD
0.09
0.39
0.28
0.32
0.18
0.23
df‘ = 5.54
0.53
0.34
0.24
0.29
0.13
0. I3
I I.312 p = 0.000
0.11
0.17
0.18
0.12
0.16
0.10
df = 5.54
Mean
0.05
0.03
0.05
0.00
0.02
0.02
p > 0.05
SD
0.08
0.07
0.08
0.00
0.05
0.05
df = 5.54
0.18 0.21
0.09 0.13
0.18 0.17
0.21 0.20
0.06 0.12
0.04 0.06
p > 0.05 df = 5.54
Mean
0.31
0.46
0.19
0.32
0.18
0.06
p = 0.000
SD
0.29
0.25
0.1 I
0.20
0.18
0.07
cif =
Substitution
Processes
Stopping Mean SD Gliding
I.042
of fricatives
2.1 I9
Affrication Mean SD Fronting
4.989 5.54
PHONOLOGICAL
Means and Standard
PROCESS
401
DEVELOPMENT
TABLE 3 Deviation for the MLU Groups.’ MLU Groups
Variable Substitution
1
2
3
4
5
6
0.1 I 0.20
0.15 0.31
0.06 0.11
0.00
0.01
0.00 0.04
0.03 0.05
0.51 0.33
0.51 0.25
0.56 0.19
0.58 0.28
0.28 0.28
0.18 0.26
0.66 0.27
0.66 0.13
0.60 0.15
0.55 0.30
0.26 0.29
0.26 0.29
F
Process
Denasalization Mean SD Gliding of liquids Mean SD Vocalization Mean SD
‘Results of analysis of variance among MLU groups for each phonological right-hand column.
1.417 p < 0.05 df = 5,54 3.951 p < 0.004 df = 5.54 8.660 p = 0.000 df = 5.54
process are given in the
< 0.05) existed for the purpose of defining the effectiveness period for each phonological process. Using the Tukey HSD analysis, the point at which a process showed a significant between-group difference, and did not show any additional between-group significance for the next two successive MLU groups was considered to be the upper boundary for the effectiveness period of that process. A summary of the sixteen phonological processes and MLU-referenced effectiveness periods is presented in Figure 1. Discussion As was reported earlier, a three-way analysis of variance was done to answer the question whether there were significant differences among each of the major phonological process groupings across age groups and MLU groups. This analysis showed significant main effects for the three major process category groupings. A Tukey’s HSD test revealed that the Syllable Structure Processes were significantly @I < 0.05) different from the Harmony and Substitution Processes. Six of the processes averaged 3555% usage across all MLU groups. Deletion of final consonants, cluster reduction, weak syllable deletion, gliding of liquids, vocalization, and final consonant devoicing appeared to be the processes which affect children’s productions to the greatest degree. With the exception of weak syllable deletion and gliding of liquids that effectively operate through MLU Group 6, these high utility processes were generally most effective when the subjects’ MLUs were less than five morphemes.
402
R. .I. PRATER
i
!
z' 0 i
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I i i i I
and R. W. SWIFT
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PHONOLOGICAL
PROCESS
DEVELOPMENT
403
Glottal replacement, alveolar assimilation, velar assimilation, gliding of fricatives, affrication, and denasalization were infrequently used by the subjects at all MLU levels with utilization never exceeding 20%. Although these were low utility processes, they were long-lasting processes that appeared across all MLU groups. These processes were generally simplification strategies employed by individual subjects and were not processes commonly used by the majority of the subjects in each MLU group. Syllable Structure
Processes
The analysis revealed that the Syllable Structure Processes-those processes that act to simplify the child’s productions to a CV or CVCV unit-were the most frequently used by children with MLU values in the lower range (Figure 2). the Syllable Structure Processes With the exception of glottal replacement, showed a consistent reduction from MLU Group 1 to MLU Group 6. Because all Syllable Structure Processes were used less than 20% of the time by the subjects in MLU Group 6, it can be concluded that the effective utility of the Syllable Structure Processes is limited to utterances produced when children have an MLU less than seven morphemes. Deletion of final consonants appeared to be an important simplification process when a child’s MLU was less than three morphemes. A significant (p < 0.05) reduction between MLU level 1 and MLU level 3 was shown with the differences among the remaining MLU levels not significant. These data are consistent with the evidence summarized by Ingram (1976) who found that final consonant deletion is generally lost between 18 mo and 36 mo. Likewise, Templin (1957) and Irwin (1951) found marked increases in the use of final consonants in children by the age of 3. Cluster reduction and weak syllable deletion were the most frequently used Syllable Structure Processes. These processes demonstrated nearly identical reduction patterns. The subjects in MLU Group 1 approximated 85% usage of both processes with a reduction to 17% by the subjects in MLU Group 6. Cluster reduction and weak syllable deletion seem to operate longer than deletion of final consonants and appear to affect syllables produced by children up to age 4 and beyond (Greenlee, 1974; Ingram, 1976; and Smith, 1973). The data in this study were in agreement. Significant decreases (p < 0.05) in usage of cluster reduction and weak syllable deletion by subjects in this study were more linear and more gradual than the reduction of deletion of final consonants. Glottal replacement was dissimilar from the other Syllable Structure Processes and appeared to play an insignificant role in children’s syllable reduction strategies. There was no significant difference (p < 0.05) between the groups for glottal replacement, and this process approximated only 9% usage across all MLU levels examined.
0.6-
1.0
r
1
Fig. 2.
Mean proportion
2
MLU
4 GROUP
Glottal
-
5
Replacement
Deletion
Reduction
Consonants
scores of the IMLU groups for the syllable structure processes
3
Weak
-
of Final
Syllable
Cluster
A-- -A
Deletion
KY-----Cl
6
PHONOLOGICAL
Harmony
PROCESS
DEVELOPMENT
405
Processes
The Harmony Processes, those processes that act to create internal symmetry in words, were used less frequently than the syllable structure processes. The Harmony Processes were, nonetheless, important phonological simplification strategies for the subjects. Final consonant devoicing was the most frequently used Harmony Process (Figure 3). Final consonant devoicing did not appear as an effective Harmony Process until the subjects had an MLU greater than two morphemes. This was anticipated because many of the utterances produced by the subjects with an MLU of 1.OO- 1.99 were “open syllable” utterances devoid of final consonants that could be devoiced. Final consonant devoicing appeared to affect the subjects’ productions most when their MLU was in the range of 2.00-4.99 morphemes. The process of final consonant devoicing was significantly (p < 0.05) reduced after the subjects had an MLU equal to or greater than five morphemes. Labial assimilation was the second most frequently used Harmony Process. Although the statistical analysis indicated significant 0, < 0.05) variance between the MLU groups, the Tukey’s a priori test revealed that the only significant difference was between MLU Group 2 and MLU Group 6. The use of labial assimilation averaged 28% across the first five MLU groups with a nonsignificant reduction for MLU Group 6. It appeared that labial assimilation operated at a similar effectiveness level for all subjects regardless of their MLU level, and that a reduction in this process must occur at higher MLU levels than those examined in this study. The Harmony Processes of alveolar and velar assimilation were infrequently used by all subjects in this study. There were no significant differences 0, > 0.05) among any of the MLU groups for alveolar assimilation. The subjects averaged 16% usage of this process across all MLU levels examined with no indication of the beginning of a reduction trend. Velar assimilation was used most frequently by the subjects with lower MLU values; this process, however, never exceeded a mean usage of 18%. There was a significant 0, < 0.05) reduction of the velar assimilation process between MLU Group I and MLU Group 3 with this process remaining at a low level throughout the remainder of the MLU levels examined. Prevocalic voicing appeared to be an effective Harmony Process only for the children in MLU Groups I and 2. This process was significantly @ < 0.05) reduced between MLU Groups 2 and 3, and was almost totally suppressed by the subjects when MLU was equal to or greater than four morphemes. This finding is in agreement with the Bond and Wilson (1980) data that showed that the voicing contrast is acquired by normal children with MLUs less than four morphemes.
406
R. J. PRATER
S3t103S
and R. W. SWIFT
NOlltlOdOtld
NV3W
PHONOLOGICAL
Substitution
PROCESS
DEVELOPMENT
407
Processes
Vocalization was the most frequently used Substitution Process by the subjects (Figure 4). When MLU was less than five morphemes, the subjects averaged 62% usage of this process. There was a significant (p > 0.05) reduction of this process between MLU Groups 4 and 5, but the process was still operable for the subjects in MLU Group 6. Gliding of liquids was also a frequently used Substitution Process. The subjects in MLU Group 1 through MLU Group 4 approximated 54% usage of this process. Although there was a decrease in the use of this process between MLU Group 1 and MLU Group 6, the reduction was not significant @ < 0.05). The gliding of liquids process appeared to continue to affect syllables produced by children with an MLU of six morphemes or greater. A demonstration of a significant reduction in the use of this process awaits further study of children with an MLU greater than 6.99 morphemes. Stopping was the second most frequently used Substitution Process for children in MLU Group 1. This process showed a significant (p < 0.05) reduction between MLU Group 1 and MLU Group 4. Above MLU Group 4 the process of stopping stabilized at a low level of usage. It appeared that this process operated most effectively when the subjects’ MLUs were below 4.99 morphemes. The process of fronting did not show a consistent pattern of reduction. Usage of the process of fronting was highly variable from one MLU group to another. Only between MLU Groups 5 and 6 was there trend toward a significant difference, with this process reducing to 6% usage in MLU Group 6. There were no significant (p < 0.05) differences among the MLU groups for gliding of fricatives, affrication, and denasalization. These were the least used of the sixteen phonological processes examined and were rarely used by subjects in this study as significant simplification strategies. They were, however, operable in all groups except MLU Group 4. Affrication appeared to be a transitional process that allowed the subjects to gradually acquire the stop-fricative contrast. It seemed as though the subjects were holding on to their “. . . old process of stopping and at the same time experimenting with a new friction feature” (Weiner, 1979, p. 5). Consequently, many target fricatives were temporarily produced as affricates (combination of a stop and a fricative). This phenomenon was demonstrated by an increase in the use of the process of affrication in MLU Groups 3 and 4. Above MLU Group 4, inappropriate stopping and affrication decreased similarly. Summary These descriptions have been presented as general guidelines regarding the development of sixteen phonological processes. It is hoped that this picture of the
408
R. J. PRATER
u__L__L__+
0
and R. W. SWIFT
1
I
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d
d
d
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PHONOLOGICAL
PROCESS
409
DEVELOPMENT
emergence, duration, elimination, and universality of the processes can be used to facilitate more accurate diagnosis and treatment of phonological disorders in children. Future research should be directed toward more closely examining the specific nature of change in individual processes in normal and disordered clinical populations. The research reported here was supported, in part, by a grant from the University of North Carolina at Greensboro Research Committee. We wish to thank the Greensboro Mini-Skools and the Wilkes County Department of Social Services for their valuable assistance in the execution of this study. References Bodine, A. (1974). A phonological Linguist.
analysis of two mongoloid
(Down’s Syndrome)
boys. Anthropol.
16: l-24.
Bond, Z., and Wilson, H. (1980). Acquisition of the voicing contrast by language-delayed and normal-speaking children. J. Speech Hear. Res. 23: 152- 16 1. Brown, R. (1973). A First Language: The Early Stages. Baltimore: University Park Press. Compton, A. (1970). Generative studies of children’s phonological disorders. J. Speech Hear. Disord.
35:315-39.
Compton, A. (1975). Generative studies of children’s phonological disorders: A strategy of therapy. In S. Singh (Ed.), Measurements in Hearing, Speech and Languae. Baltimore: University Park Press. Cracker, J. (1969). A phonolopical model of children’s articulation competence. J. Speech Hear. Dim-d.
Greenlee,
34:203-
13.
M. (1974). Interacting
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in the child’s acquisition
of stop-liquid
clusters. Pap.
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Haas, W. (1963). Phonoloical analysis of a case of dyslalia. J. Speech Hear. Disord. Z&239-46. Ingram, D. (1974). Phonological rules in young children. J. Child Lang. 1:49-64. Ingram, D. (1976). Phonological Disability in Children. New York: Elsevier. Irwin, 0. (1951). Infant speech: Consonantal position. J. Speech Hear. Disord. 16: 159-61. Kornfeld, J. (1971). Theoretical issues in child phonology. In Papers from the Sevenfh Regional Meefing of the Chicago Linguistics Sociely. pp. 454-68. Lorentz, J. (1974). A deviant phonological system of English. Pap. Rep. Child Lang. Dev. 8:55-64.
McReynolds, J. Speech
L., and Bennett, S. (1972). Distinctive Hear.
Disord.
feature generalization
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37~462-70.
McReynolds, L., and Huston, K. (1971). A distinctive feature analysis of children’s misarticulations. J. Speech Hear. Disord. 36:155-66. Menn, L. (1971). Phonotactic rules in beginning speech. Lingua 26:245 -51. hlenyuk, P., and Looney, P. (1972). Relationships among components of the grammar in language disorder. J. Speech Hear. Res. 15:395-406. Moskowitz, A. (1970). The two-year-old stage in the acquisition of English phonology. Lang. 46:426-41. Oiler, D. (1973). Regularities in abnormal child phonology. J. Speech Hear. Disord. 38:36-47. Oller, D., and Kelly, C. (1974). Phonological processes of a hard-of-hearing child. J. Speech Hear. Disord.
39~65-74.
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R. J. PRATER
and R. W. SWIFT
Pollock. E.. and Ree, N. (1972). Disorders of articulation: Some clinical applications of distinctive feature theory. .I. Speech Hear. Disord. 37:451-61. Poole, I. (1934). Genetic development of articulation of consonant sounds in speech. Elrnt. English Rev. 11:159-161. Prather, E. M.. Hendrick. D. L., and Kern, C. A. (1975). Articulation development in children aged two to four years. .I. Speech Hear. Dimrd. 40: 179% I9 I. Schwartz, R., and Folger, M. (1977). Phonoloical Behavror in Notwnl ami Lmguuge Dtsordered Children. Unpublished paper, Memphis State University. Shriner, T., Halloway, M., and Daniloff. R. (1969). The relationship between articulatory defects and syntax in speech defective children J. Specvh Hear Res. 12:3 19 -325. Smith, N. (1973). The Acquisition ofPhonologyv: A Case Study. Cambridge: Cambridge University Press. Stampe, D. (1969). The acqutsition of phonetic representation. In Papcrs.frorn the Ffth Rrgiowd Meeting of the Chicago Linguistic Society. pp. 443-54. Templin, M. (1957). Certain language skills in children: Their development and interrelationships. ltwiture of Child Welfare Monograph 26. Minneapolis: University of Minnesota Press. Waterson, N. (1971). Child phonology: A prosodic view. .I. Linguistics 7: 170-221. Weiner, F. (1979). P,‘xmological Process Analysis. Baltimore: University Park Press. Wellman, B.. Case. I.. Mengert, I.. and Bradbury, D. (1931). Speech sounds of young children. Urtiversity of Imu Study of Child Welfura 5: I-82. West, J., and Weber, A. (1973). A phonological analysis of the spontaneous language of a four-year-old, hard-of-hearing child. J. Speech Hear. Disord. 38:25-35. Whitacre, J., Luper. H., and Pollio. H. (1970). General language deficits in children with articulation problems. Lang. Spcwh 13:231-239.
OF COMMUNICATION
DISORDERS
395
15 (1982), 395-410
PHONOLOGICAL PROCESS MLU-REFERENCED
DEVELOPMENT GUIDELINES
WITH
REX JOE PRATER The Universiry of North Carolina at Greensboro
ROGER Rockingham
WILLIAMS
SWIFT
County Enrichment
Center
Sixty subjects between the ages of 2 1 and 48 months were placed into groups based on mean length of utterance (MLU) and chronological age (CA) to test Stampe’s hypothesis about the development of phonological processes. The subjects were given the Phonological Process Analysis (Weiner, 1979). and a proportion score for each of sixteen phonological processes was derived for each subject. The use of the various phonological processes across MLU groups and age groups was analyzed by multiple regression correlation, three-way ANOVA, and Tukey’s HSD tests. MLU was found to be the best classification for the subjects for describing the phonological processes. The results and discussions present MLU-referenced guidelines regarding the emergence, duration, elimination, and universalitv of the sixteen ohonoloeical orocesses.
Introduction
Stampe (1969) suggests that in attempting to produce adult words, children reduce them to simpler patterns through an innate system of phonological processes. According to this hypothesis, phonological acquisition is seen as the suppression and elimination of these simplifying tendencies. The purpose of this study was to examine Stampe’s hypothesis using MLU and chronological age for classifying the subjects and the Phonological Process Analysis (Weiner, 1979) to obtain measures. The use of chronological age for describing phonological acquisition has had considerable historical precedent (Poole, 1934; Prather et al., 1975; Templin, 1957; Wellman et al., 1931). The use of MLU for analysis of phonological acquisition was in keeping with the research findings of Menyuk and Looney ( 1972), Schwartz and Folger (1977), Shriner et al., (1969), and Whitacre et al. (1970). who have suggested a complex interaction between various aspects of linguistic acquisition, including phonology. Several studies (Ingram, 1974; Kornfeld, 1971; Menn, 1971; Moskowitz, 1970; Smith, 1973; Waterson, 1971) have attempted to use phonological analysis
Address correspondence
to Rex J. Prater, Ph.D.,
D Elsevier Science Publishing Company, Inc., 52 Vanderbilt Ave., New York, NY 10017
3 Amberhill
Court, Greensboro,
NC 27405.
1982 0021-9924/82/050395-16$02.75
396
R. J. PRATER
and R. W. SWIFT
to describe the speech of normal children. Likewise, the utility of using phonological analysis in case studies of children with articulation disorders has been demonstrated (Bodine, 1974; Haas, 1963; Lorentz, 1974; Oiler and Kelly. 1974; West and Weber. 1973). Even though phonological milestones have not been fully determined, attempts at using phonological analysis for purposes of therapeutic intervention have been made (Compton, 1970. 1975; Cracker, 1969; McReynolds and Bennet. 1972; McReynolds and Huston, 197 I; Oller, 1973; Pollock and Rees. 1972). Knowledge about normal phonological development in children is far from complete. If Stampe’s natural phonology theory is correct, there is a need to know more about the emergence, duration, elimination, and universality of each of the phonological processes. The developmental relationship between these processes is presently undefined. Method Subjects
The subjects in the study were 60 children ranging in age from 21 to 48 mo. To be accepted as a subject for this study, each child must have been reared since birth in a home where English was spoken as the first language and must not appear to have any hearing defects or neurological problems as observed by the examiners. Stimulus Materials and Prowdurc~s
The Phonological Process Analysis (Weiner, 1979) was administered to each subject. This test consists of 142 line drawings of objects and actions that the subjects named after an indirect verbal model was presented by the examiner (e.g., Uncle Fred is wearing a hat. What is Uncle Fred wearing?). The picture stimuli of the Phonological Process Analysis are grouped into subtests designed to elicit one of 16 phonological processes. Twelve of the process subtests have 8 stimulus items, three have 6 items, and one subtest has 28 items. The process subtests are grouped under three major categorical headings: (1) Syllable Structure Processes, which includes the subtests of deletion of final consonants, cluster reduction, weak syllable deletion, and glottal replacement; (2) Harmony Processes, which includes labial, alveolar and velar assimilation, prevocalic voicing. and final consonant devoicing; and (3) Substitution Processes with the subtests of stopping, gliding of fricatives, affrication. fronting, denasalization, gliding of liquids, and vocalization.
PHONOLOGICAL
PROCESS
DEVELOPMENT
391
Score Derivation The verbal responses of each subject to the picture stimuli of the Phonological Process Analysis were phonetically transcribed on a score sheet immediately following each response. The verbal responses were recorded on audiotape for later verification of transcription accuracy. An item-by-item analysis of interjudge reliability for fifteen subjects ’ total responses was 91%. Intra-judge reliabilities for scoring three subjects’ total responses after a seven-day interval were 94% and 95% for the two examiners. Subjects’ scores for each process on the Phonological Process Analysis were derived as a percentage of the number of times the subject demonstrated the process to the total number of times the process was specifically tested in any one subtest. Results For purpose of analysis, the subjects were grouped by MLU and by chronological age (CA). There were six equal MLU groups with each group having a range of one morpheme. Total range for all MLU groups was 1.00 to 6.99 morphemes. MLU was calculated according to the method of Brown (1973). Seven age groups were also used for classifying the subjects. Each age group had a range of 4 mo and the total range for all age groups was 2 1 to 48 mo. Mean age and MLU for the groups are presented in Table 1.
TABLE I Mean Age and Mean MLU for Groupings
Grouping Age Age Age Age Age Age Age MLU MLU MLU MLU MLU MLU
Group Group Group Group Group Group Group Group Group Group Group Group Group
N
Mean Age in Months
Used in the Data Analysis
Mean MLU
SD
-
1.94 3.29 3.51 4.88 5.56 6.55 5.89
I .09 1.27 1.26 I .64 0.50 0.00 0.10
5.23 2.70 3.85 4.04 6.55 4.13
-
-
SD
I
10
-
2 3 4 5 6 7
10 16 12 7 2 3
-
1 2 3 4 5 6
10 10 10 10 10 IO
24.9 27.1 30.5 30.5 37.6 37.5
R. J. PRATER
398
Edunting
thr Rdatiw
Strc~ngth.r
anti R. W. SWIFT
of MLU
trtd CA jot- Description
Purposes To evaluate whether MLU or CA was a better measure for describing the development of the phonological processes. a hierarchical multiple regression correlation of the subjects’ scores for each phonological process with age groups and MLU groups was performed. In a hierarchical multiple regression correlation, the variables that have higher inclusion level values are brought into the equation before variables with lower inclusion values. By examining whether age groups or MLU groups were drawn into the regression analysis more frequently as the higher inclusion level variable and by examining the change in the squared ip value when the second variable was included, an evaluation of the relative strengths processes
of age grouping and MLU was accomplished.
grouping
for describing
the phonological
For the ten phonological processes that were significantly (p < 0.01) related to either age or MLU groups, MLU group was the higher inclusion-level variable drawn into the regression analysis for seven phonological processes, and age group was the higher variable was drawn into the regression
for just three processes (Table 2). When age group as the lower inclusion-level variable, the change in
the squared r values was never more than 1%. To exarnine further whether MLU grouping or age grouping better described use of the phonological processes. an average score for each subject for each of three major categorical headings (Syllable Structure Processes. Harmony Processes, and Substitution Processes) was computed by calculating the mean of all subtest scores for each subject under each major categorical heading. A three-way analysis of variance was performed to determine whether the average score for each of three major process categories across age groups and MLU groups was different. Significant main effects
for the three major categories
(F = 43.418; d! = 2,54;p = 0.000) = 0.000) were found. No significant 5,54; p 1 0.05) was demonstrated.
of phonological
process
and MLU groups (F = 11.018; cif = 5,54; p main effect of age groups (F = 1.687; elf = In addition, a significant MLU group x
Major Process Category two-way interaction (F = 6.632; df = 10,54; p = 0.000) revealed that differences in subjects’ scores occurred on the basis of an interaction among varying levels of MLU grouping and the major process categories. Therefore, because MLU group was drawn into the multiple regression correlation equation rnore frequently as the higher inclusion-level variable and because the regression data and the three-way analysis of variance data were in agreement, MLU grouping was chosen as the more accurate classification method for describing processes.
the development
of the majority
of the phonological
PHONOLOGICAL
PROCESS
399
DEVELOPMENT
TABLE 2 Sample Regression Coefficients (b), Multiple Correlation (R), and R* for Regression of Proportion Scores for the IO Phonological Processes that Were Significantly @ < 0.05) Related to Age Groups and/or MLU Groups (Xl R
R2
-0. I1 -
-0.60 -0.59
0.36 0.35
-0.47 -0.71
-0.36
-0.76 -0.71
0.57 0.50
Age
-0.67 -0.70
-0.42
-0.70 -0.70
0.49 0.49
Age MLU
MLU
-0.31 -0.37
-0.09 -
-0.38 -0.37
0.14 0.14
Velar assimilation
MLU Age
Age
-0.39 -0.47
-0.12 -
-0.47 -0.47
0.23 0.22
Prevocalic
MLU Age
Age
-0.42 -0.44
-0.03
-0.44 -0.44
0.19 0.19
Ane
’
-0.58
-0.58
0.34
Stopping
MLU Age
Age
-0.38 -0.49
-0.17 -
-0.51 -0.49
0.26 0.24
Fronting
MLU Age
Age
-0.30 -0.40
-0.16
-0.42 -0.40
0.18 0.16
Vocalization
Age MLU
MLU
-0.51 -0.56
-0.07
-0.56 -0.56
0.32 0.31
Phonological
Process
X/
x2
b,
MLU Age
Age
-0.66 -0.59
MLU Age
Age
MLU Age
Alveolar assimilation
Deletion of final consonants
Cluster reduction
Weak syllable deletion
voicing
Final consonant devoicing
‘F-level
or tolerance
level insufficient
Effects of Increased
for computation
MLU on Process
4
of second variable.
Usage
To examine the effects of increased MLU on subjects’ scores for each phonological process, a statistical analysis of variance for each process was performed. Significant differences (p < 0.05) were found among MLU groups for all but five processes--glottal replacement, alveolar assimilation, gliding of fricatives, affrication, and denasalization (Table 3). The MLU group data for each phonological process were analyzed using Tukey’s “honestly significant difference” test. This analysis was used to determine homogenous subsets of the MLU groups with regard to each process, and to determine between which pairs of MLU groups significant differences (p
400
R. J. PRATER
and R. W. SWIFT
TABLE Means
and Standard
Deviation
for the MLU
3
Groups.” M LU Groups
I
Variable Svllable
Structure
Deletion
3
4
5
6
0.90
0.62
0.32
0.23
0.08
0.07
p = 0.000
0.08
0.27
0.31
0.29
0.09
0.07
llf = s.54
0.87
0.80
0.63
0.58
0.28
0.17
17 = 0.000
0.09
0.12
0.22
0.28
0.27
0.15
df = 5,54
0.83
0.80
0.63
0.50
0.35
0.18
p = 0.000
0.14
0.07
0.21
0.21
0.24
0.15
c/f = 5.54
0.09
0.15
0.09
0.03
0.15
0.04
0.13
0.21
0. IO
0.08
0.31
0.08
(If =
0.28
0.39
0.28
0.38
0.28
0.1 I
p < 0.038
0.18
0.17
0.20
0.22
0.23
0.16
q
Processes
of final
23.455
consonants
Mean SD Cluster
F
2
19.21 I
reduction
Mean SD Weak syllable Mean SD Glottal
20.709
deletion
replacement
Mean SD Harmonv
0.9.52 p > 0.05 5.54
Processes
Labial
2.551
assimilation
Mean SD Alveolar
= 5.54 0.881
assimilation
Mean
0.25
0.18
0.13
0.17
0.13
0.11
p < 0.05
SD
0.21
0.18
0.17
0.18
0.15
0.10
0.29
0. I6
0.09
0.06
0.09
0.01
p = 0.000
0.18
0.12
0.08
0.07
0.13
0.04
df =
Velar
7.381
assimilation
Mean SD Prevocalic Mean SD Final
consonant
5.54
3.990
voicing 0.26
0.26
0.08
0.01
0.03
0.05
p < 0.004
0.27
0.34
0.1 I
0.04
0.05
0.07
df =
5.54
9.545
devoicing
Mean
0.08
0.66
0.51
0.59
0.14
0.13
p = 0.000
SD
0.09
0.39
0.28
0.32
0.18
0.23
df‘ = 5.54
0.53
0.34
0.24
0.29
0.13
0. I3
I I.312 p = 0.000
0.11
0.17
0.18
0.12
0.16
0.10
df = 5.54
Mean
0.05
0.03
0.05
0.00
0.02
0.02
p > 0.05
SD
0.08
0.07
0.08
0.00
0.05
0.05
df = 5.54
0.18 0.21
0.09 0.13
0.18 0.17
0.21 0.20
0.06 0.12
0.04 0.06
p > 0.05 df = 5.54
Mean
0.31
0.46
0.19
0.32
0.18
0.06
p = 0.000
SD
0.29
0.25
0.1 I
0.20
0.18
0.07
cif =
Substitution
Processes
Stopping Mean SD Gliding
I.042
of fricatives
2.1 I9
Affrication Mean SD Fronting
4.989 5.54
PHONOLOGICAL
Means and Standard
PROCESS
401
DEVELOPMENT
TABLE 3 Deviation for the MLU Groups.’ MLU Groups
Variable Substitution
1
2
3
4
5
6
0.1 I 0.20
0.15 0.31
0.06 0.11
0.00
0.01
0.00 0.04
0.03 0.05
0.51 0.33
0.51 0.25
0.56 0.19
0.58 0.28
0.28 0.28
0.18 0.26
0.66 0.27
0.66 0.13
0.60 0.15
0.55 0.30
0.26 0.29
0.26 0.29
F
Process
Denasalization Mean SD Gliding of liquids Mean SD Vocalization Mean SD
‘Results of analysis of variance among MLU groups for each phonological right-hand column.
1.417 p < 0.05 df = 5,54 3.951 p < 0.004 df = 5.54 8.660 p = 0.000 df = 5.54
process are given in the
< 0.05) existed for the purpose of defining the effectiveness period for each phonological process. Using the Tukey HSD analysis, the point at which a process showed a significant between-group difference, and did not show any additional between-group significance for the next two successive MLU groups was considered to be the upper boundary for the effectiveness period of that process. A summary of the sixteen phonological processes and MLU-referenced effectiveness periods is presented in Figure 1. Discussion As was reported earlier, a three-way analysis of variance was done to answer the question whether there were significant differences among each of the major phonological process groupings across age groups and MLU groups. This analysis showed significant main effects for the three major process category groupings. A Tukey’s HSD test revealed that the Syllable Structure Processes were significantly @I < 0.05) different from the Harmony and Substitution Processes. Six of the processes averaged 3555% usage across all MLU groups. Deletion of final consonants, cluster reduction, weak syllable deletion, gliding of liquids, vocalization, and final consonant devoicing appeared to be the processes which affect children’s productions to the greatest degree. With the exception of weak syllable deletion and gliding of liquids that effectively operate through MLU Group 6, these high utility processes were generally most effective when the subjects’ MLUs were less than five morphemes.
402
R. .I. PRATER
i
!
z' 0 i
C i
I i i i I
and R. W. SWIFT
i i i i I
z z I
PHONOLOGICAL
PROCESS
DEVELOPMENT
403
Glottal replacement, alveolar assimilation, velar assimilation, gliding of fricatives, affrication, and denasalization were infrequently used by the subjects at all MLU levels with utilization never exceeding 20%. Although these were low utility processes, they were long-lasting processes that appeared across all MLU groups. These processes were generally simplification strategies employed by individual subjects and were not processes commonly used by the majority of the subjects in each MLU group. Syllable Structure
Processes
The analysis revealed that the Syllable Structure Processes-those processes that act to simplify the child’s productions to a CV or CVCV unit-were the most frequently used by children with MLU values in the lower range (Figure 2). the Syllable Structure Processes With the exception of glottal replacement, showed a consistent reduction from MLU Group 1 to MLU Group 6. Because all Syllable Structure Processes were used less than 20% of the time by the subjects in MLU Group 6, it can be concluded that the effective utility of the Syllable Structure Processes is limited to utterances produced when children have an MLU less than seven morphemes. Deletion of final consonants appeared to be an important simplification process when a child’s MLU was less than three morphemes. A significant (p < 0.05) reduction between MLU level 1 and MLU level 3 was shown with the differences among the remaining MLU levels not significant. These data are consistent with the evidence summarized by Ingram (1976) who found that final consonant deletion is generally lost between 18 mo and 36 mo. Likewise, Templin (1957) and Irwin (1951) found marked increases in the use of final consonants in children by the age of 3. Cluster reduction and weak syllable deletion were the most frequently used Syllable Structure Processes. These processes demonstrated nearly identical reduction patterns. The subjects in MLU Group 1 approximated 85% usage of both processes with a reduction to 17% by the subjects in MLU Group 6. Cluster reduction and weak syllable deletion seem to operate longer than deletion of final consonants and appear to affect syllables produced by children up to age 4 and beyond (Greenlee, 1974; Ingram, 1976; and Smith, 1973). The data in this study were in agreement. Significant decreases (p < 0.05) in usage of cluster reduction and weak syllable deletion by subjects in this study were more linear and more gradual than the reduction of deletion of final consonants. Glottal replacement was dissimilar from the other Syllable Structure Processes and appeared to play an insignificant role in children’s syllable reduction strategies. There was no significant difference (p < 0.05) between the groups for glottal replacement, and this process approximated only 9% usage across all MLU levels examined.
0.6-
1.0
r
1
Fig. 2.
Mean proportion
2
MLU
4 GROUP
Glottal
-
5
Replacement
Deletion
Reduction
Consonants
scores of the IMLU groups for the syllable structure processes
3
Weak
-
of Final
Syllable
Cluster
A-- -A
Deletion
KY-----Cl
6
PHONOLOGICAL
Harmony
PROCESS
DEVELOPMENT
405
Processes
The Harmony Processes, those processes that act to create internal symmetry in words, were used less frequently than the syllable structure processes. The Harmony Processes were, nonetheless, important phonological simplification strategies for the subjects. Final consonant devoicing was the most frequently used Harmony Process (Figure 3). Final consonant devoicing did not appear as an effective Harmony Process until the subjects had an MLU greater than two morphemes. This was anticipated because many of the utterances produced by the subjects with an MLU of 1.OO- 1.99 were “open syllable” utterances devoid of final consonants that could be devoiced. Final consonant devoicing appeared to affect the subjects’ productions most when their MLU was in the range of 2.00-4.99 morphemes. The process of final consonant devoicing was significantly (p < 0.05) reduced after the subjects had an MLU equal to or greater than five morphemes. Labial assimilation was the second most frequently used Harmony Process. Although the statistical analysis indicated significant 0, < 0.05) variance between the MLU groups, the Tukey’s a priori test revealed that the only significant difference was between MLU Group 2 and MLU Group 6. The use of labial assimilation averaged 28% across the first five MLU groups with a nonsignificant reduction for MLU Group 6. It appeared that labial assimilation operated at a similar effectiveness level for all subjects regardless of their MLU level, and that a reduction in this process must occur at higher MLU levels than those examined in this study. The Harmony Processes of alveolar and velar assimilation were infrequently used by all subjects in this study. There were no significant differences 0, > 0.05) among any of the MLU groups for alveolar assimilation. The subjects averaged 16% usage of this process across all MLU levels examined with no indication of the beginning of a reduction trend. Velar assimilation was used most frequently by the subjects with lower MLU values; this process, however, never exceeded a mean usage of 18%. There was a significant 0, < 0.05) reduction of the velar assimilation process between MLU Group I and MLU Group 3 with this process remaining at a low level throughout the remainder of the MLU levels examined. Prevocalic voicing appeared to be an effective Harmony Process only for the children in MLU Groups I and 2. This process was significantly @ < 0.05) reduced between MLU Groups 2 and 3, and was almost totally suppressed by the subjects when MLU was equal to or greater than four morphemes. This finding is in agreement with the Bond and Wilson (1980) data that showed that the voicing contrast is acquired by normal children with MLUs less than four morphemes.
406
R. J. PRATER
S3t103S
and R. W. SWIFT
NOlltlOdOtld
NV3W
PHONOLOGICAL
Substitution
PROCESS
DEVELOPMENT
407
Processes
Vocalization was the most frequently used Substitution Process by the subjects (Figure 4). When MLU was less than five morphemes, the subjects averaged 62% usage of this process. There was a significant (p > 0.05) reduction of this process between MLU Groups 4 and 5, but the process was still operable for the subjects in MLU Group 6. Gliding of liquids was also a frequently used Substitution Process. The subjects in MLU Group 1 through MLU Group 4 approximated 54% usage of this process. Although there was a decrease in the use of this process between MLU Group 1 and MLU Group 6, the reduction was not significant @ < 0.05). The gliding of liquids process appeared to continue to affect syllables produced by children with an MLU of six morphemes or greater. A demonstration of a significant reduction in the use of this process awaits further study of children with an MLU greater than 6.99 morphemes. Stopping was the second most frequently used Substitution Process for children in MLU Group 1. This process showed a significant (p < 0.05) reduction between MLU Group 1 and MLU Group 4. Above MLU Group 4 the process of stopping stabilized at a low level of usage. It appeared that this process operated most effectively when the subjects’ MLUs were below 4.99 morphemes. The process of fronting did not show a consistent pattern of reduction. Usage of the process of fronting was highly variable from one MLU group to another. Only between MLU Groups 5 and 6 was there trend toward a significant difference, with this process reducing to 6% usage in MLU Group 6. There were no significant (p < 0.05) differences among the MLU groups for gliding of fricatives, affrication, and denasalization. These were the least used of the sixteen phonological processes examined and were rarely used by subjects in this study as significant simplification strategies. They were, however, operable in all groups except MLU Group 4. Affrication appeared to be a transitional process that allowed the subjects to gradually acquire the stop-fricative contrast. It seemed as though the subjects were holding on to their “. . . old process of stopping and at the same time experimenting with a new friction feature” (Weiner, 1979, p. 5). Consequently, many target fricatives were temporarily produced as affricates (combination of a stop and a fricative). This phenomenon was demonstrated by an increase in the use of the process of affrication in MLU Groups 3 and 4. Above MLU Group 4, inappropriate stopping and affrication decreased similarly. Summary These descriptions have been presented as general guidelines regarding the development of sixteen phonological processes. It is hoped that this picture of the
408
R. J. PRATER
u__L__L__+
0
and R. W. SWIFT
1
I
I
I
03
d
N
d
d
d
d S3t103S
NOI 1tlOdOtld
NV3W
1
J
0
PHONOLOGICAL
PROCESS
409
DEVELOPMENT
emergence, duration, elimination, and universality of the processes can be used to facilitate more accurate diagnosis and treatment of phonological disorders in children. Future research should be directed toward more closely examining the specific nature of change in individual processes in normal and disordered clinical populations. The research reported here was supported, in part, by a grant from the University of North Carolina at Greensboro Research Committee. We wish to thank the Greensboro Mini-Skools and the Wilkes County Department of Social Services for their valuable assistance in the execution of this study. References Bodine, A. (1974). A phonological Linguist.
analysis of two mongoloid
(Down’s Syndrome)
boys. Anthropol.
16: l-24.
Bond, Z., and Wilson, H. (1980). Acquisition of the voicing contrast by language-delayed and normal-speaking children. J. Speech Hear. Res. 23: 152- 16 1. Brown, R. (1973). A First Language: The Early Stages. Baltimore: University Park Press. Compton, A. (1970). Generative studies of children’s phonological disorders. J. Speech Hear. Disord.
35:315-39.
Compton, A. (1975). Generative studies of children’s phonological disorders: A strategy of therapy. In S. Singh (Ed.), Measurements in Hearing, Speech and Languae. Baltimore: University Park Press. Cracker, J. (1969). A phonolopical model of children’s articulation competence. J. Speech Hear. Dim-d.
Greenlee,
34:203-
13.
M. (1974). Interacting
Rep. Child Lang. Dev.
7:85-
processes
in the child’s acquisition
of stop-liquid
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