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Linguistic and Articulatory Aspects of Single Word Production in Apraxia of Speech
LINGUISTIC AND ARTICULATORY ASPECTS OF SINGLE WORD PRODUCTION IN APRAXIA OF SPEECH' Jeanette M. Dunlop and Thomas P. Marquardt (Department of Audiology and Speech Pathology, University of Tennessee, Knoxville, Tennessee)
INTRODUCTION
For more than a century investigators have been unable to agree whether apraxia of speech is a motor programming disorder devoid of linguistic components or a phonological disorder without a discrete separation from other language processes. Most recent investigations (Johns and Darley, 1970; Aten, Johns and Darley, 1971; Deal and Darley, 1972; Rosenbek, Wertz and Darley, 1973; LaPointe and Johns, 1975) have described apraxia as a non-linguistic motor programming disorder without significant speech musculature weakness, slowness, or incoordination. However, Martin and Rigrodsky {197 4) found that a group of aphasics with phonological impairments made more phoneme errors when they were asked to repeat meaningless stimuli rather than meaningful stimuli and concluded that the semantic component of words may significantly aid in the motor production of phonemes. Martin (1974) hypothesized that" ... the influence of other linguistic variables on phonological production demonstrates that there is not a discrete separation of motor acts from other language processes. or their possible impairment." He suggested further that the repetitions, blocks and groping behaviors of apraxics toward correct production were similar to other aphasic behaviors clearly showing difficulty in processing of linguistic units. In response, Aten, Darley, Deal and Johns (1975) indicated that defining apraxia as a motor programming disorder not primarily due to impairment of sensory, intellectual or higher language functioning: " ... does not assert that speech and language are unrelated or that phonological impairment is wholly uninfluenced by language functioning, but it does suggest that programming of phoneme production can be selectively impaired without impairment of language functioning." , A portion of this research was presented at the Convention of the AmeriCan Speech and Hearing Association, Washington, D.C., 1975. Preparation of this manuscript was supported, in part, by the University of Tennessee Neuropathology Services Program. l.nrtf'Y I1CJ77\
n
17.,Q
18
]. M . Dunlop and T. P. Marquardt
The hypothesized link between linguistic processes and apraxia of speech, however, has not been adequately explored. The purposes of this research were: (1) to investigate the effects of grammatical word class, phoneme position, and phoneme difficulty on the errors of apraxic speakers, and (2) to determine the relationship between word abstraction and the errors of apraxic speakers on monosyllabic words.
STUDY
1
Material and method Subjects
Ten adults, with a history of left cortical damage and articulatory characteristics indicative of apraxia of speech (LaPointe and Johns, 1975), served as subjects (Table I). TABLE I
Age, Sex, Etiology of Brain Damage, and Duration Since Onset of Symptoms for Sub;ects with Apraxia of Speech (CV A = cerebrovascular accident)
Subject
1 2 3
4 5 6 7 8 9 10
Age (years)
Sex
Etiology
Duration (months)
61 69 50 55' 55 57 57 29 42 60
F F
eVA eVA eVA eVA eVA eVA eVA Head injury eVA eVA
18 27 17 12 10
M M M M M M
F F
3 8
26 4 80
Each subject demonstrated hearing acuity within normal1imits at 500, 1000 ancl2000 Hz (ISO) in the better ear, no significant auditory comprehension difficulties as measured by their ability to respond correctly to ten items (two items each fromSubtests I, II, III and IV and one item each from Subtests V and VI) selected from the Revised Token Test (McNeil, 1973), auditory comprehension skills superior to oral expression, and no history of dementia, previous speech problems, or retardation. The subjects were native speakers of English and at least three months post brain trauma. They ranged in age from 29 to 69 years with a mean age of 53.5 years.
Word production in apraxia of spe~ch
19
Stimuli
Stimuli were 144 monosyllabic words divided into two Lists of 72 words each. List I contained equal numbers of nouns, verbs and adjectives each of which included one of six phonemes (/v/, Izl, lSI, ItSI, Id3/, Ie/) judged to be difficult for apraxic speakers to produce (Shankweiler and. Harris, 1966; Johns and Darley, 1970). Each of the six phonemes appeared in either the initial or final position of the stimulus word. Therefore, each grammatical category contained a test phoneme in four words, two with the selected phoneme in the initial position and two with the phoneme in the final position. List II was constructed similarly but contained six phonemes (/t/, Idl, Ibl, IkJ, Ip/, In/) judged to be easy for apraxic speakers to produce (Johns and Darley, 1970). Fotty of the stimulus words were used in more than one grammatical category (i.e., march - verb; march - noun). Four two syllable words were included in the Lists due to difficulty in meeting criteria for grammatical category. All words had frequencies of occurrence ofapproxima.tely 50 in a million words according to the Thorndike-Lorge List (1944) and the Carroll, Davies and Rickman List (1971).
Procedures
The words from Lists I and II were randomized and then presented to the subjects. Each word was included at or near the end of a sentence constructed of five or less words. Each sentence was presented twice. For the first presentation the sentence was read in its entirety; during the second presentation the stimulus word was omitted. The subject's task was to orally produce the omitted word. Responses were tape-recorded for later analysis.
Analysis
Each test word produced by the apraxic subjects was judged twice. First, for correct production of the test phoneme and second for correct production of the entire word. Phonemes were judged to be in error if they were: (1) distorted, (2) repeated, (3) omitted, (4) self-corrected, (5) prolonged, (6) substituted for, (7) unintelligible, (8) included within a blend. Production of the word was considered incorrect if any of the following were noted: ( 1) phoneme repetition, (2) word repetition, (3) phoneme addition, (4) phoneme substitution, (5) self-correction, (6) pause before or within the word, (7) phoneme prolongation, (8) phoneme omission, (9) phoneme distortion, (10) unintelligible response or no response (Deal and Darley, 1972). Although more than one of the categories for production errors could be recorded for a subject's response, only one possible error per phoneme or word was tabulated for statistical analysis.
Reliability
Agreement ratios were computed for phoneme and word evaluations by utilizing the formula:
]. M. Dunlop and T. P. Marquardt
20
·l· ReIiabIlty =
Agreements -,--Agreements + Differences .
Intrajudge reliability for five of the tape-recorded samples re-judged by the investigator two weeks following the initial judging was .89 for the phoneme evaluation and .90 for the word evaluation. Interjudge reliability, determined from analysis of the same five tapes by a graduate student in speech pathology, was .83 for the phoneme evaluation and .85 for the word evaluation.
Results
Error scores were tabulated for each of the apraxic subjects. Means, standard deviations, and ranges for difficulty, position and grammatical class error scores from the phoneme and word evaluations are presented in Table II. TABLE II
Means, Standard Deviations, and Ranges of Error Scores for Position, Difficulty, and Grammatical Class from Phoneme and Word Evaluations Evaluation
Variable
PhonelIle
Position Difficulty Class
Word
Position Difficulty Class
Initial Final Easy Difficult Noun Verb Adjective Initial Final Easy Difficult Noun Verb Adjective
Mean
S.D.
Range
30.6 31.2 24.5 37.3 19.7 20.6 21.5 40.3 41.5 36.7 45.1 25.4 27.1 29.3
24.6 28.6 25.8 26.0 18.8 17.9 16.8 24.4 24.8 24.8 23.7 17.3 16.6 15.3
9-69 4-72 5-69 7-72 3-48 4-47 4-47 13-72 11-72 9-72 13-72 7-48 9-48 5-48
A Treatment X Treatment X Treatment X Subjects analysis of variance was utilized to evaluate the effects of these variables on the error scores of the apraxic subjects. Difficulty
The effects of difficulty were significant for both the phomene (F = 12.783; d.f. 1, 9; P < .01) and word (F = 6.720; d.£. 1, 9; P < .05)
Word production in. apraxia 01 speech
21
evaluations. These results suggest that it was easier for the subjects to produce .. easy" phonemes or words containing these phonemes than "difficult" phonemes or words containing "difficult" phonemes (Figure 1). Mean error •
o
50
EASY
DIFFICULT
45 40 CI)
a::
0
a: a:
35 30
.....
25
"".....
20
<{
:;:
15 10 5
0
Fig. 1 -
PHONEME
WORD
Easy and difficult phoneme mean error scores from phoneme and word evaluations.
scores for the "easy" phonemes were 24.5 for the phoneme evaluation and 36.7 for the word evaluation. Mean error scores for the" difficult" phonemes were 37.3 for the phoneme evaluation and 45.1 for the word evaluation.
Position Position was not found to be a significant factor in either the phoneme (F = .032; d.£. 1, 9; p> .05) or word evaluation (F = 0401; d.£. 1, 9; P > .05). Examination of Figure 2 reveals that the mean errors for the initial and final position were almost identical; 30.,6 vs. 31.2 for the phoneme •
••
o
••
PHONEME Fig. 2 -
INITIAL FINAL
WORD
Initial and final position mean error scores from phoneme and word evaluations.
22
]. M. DunlopandT. P. Marquardt
evaluation and 40.3 vs. 41.5 for the. word evaluation. Apparently, the position of the phoneme did not significantly affect the errors of the apraxic speakers. Grammatical class
Class was not found to be significant from either ' the phoneme (F = 2.218; d.f. 2, 18, P > .05) or word evaluation (F = 3.370 ; d.f. 2, 18; p> .05). However, examination of Figure 3 reveals a trend in which the subjects produced the least errors on nouns followed by verbs and then
'"
a:
50
o
45
f:a VERBS
40
•
NOUNS ADJECTIVES
35
0
a: 30 a: u.o
25
Z
20
«
u.o
::iE
'1·5 10
:; 0
PHONEME Fig. 3 -
WORP '
Noun, verb and adiective mean error scores from phoneme and word evaluations.
adjectives. Error means were 19.7 for nouns, 20.6 for verbs and 21.5 for adjectives from the phoneme evaluation and 25.4 for nouns, 27.1 for verbs and 29 .3 for adjectives from the word evaluation. Interestingly, none of the interactions between difficulty, position and grammatical class were significant. Subjects
Substantial variability between the apraxic subjects selected for this study was noted. Examination of Figure 4 reveals that total errors from the phoneme evaluation ranged from 15 to 141 out of a possible 144, while total errors from the word evaluation ranged from 27 to 144. Additionally, interactions between the subjects and variables under study were noted. For example, from the phoneme evaluation, it was observed that six of the subjects found the final position more difficult than the initial position, while the other four subjects found the initial position more difficult than the final positibn. Similar interaction patterns between subjects and difficulty w~re noted. These
23
Word production in apraxia of speech
findings suggest that within group variability may contribute to the di$culty encountered in studying apraxic subjects. 150 140 130 120 110
a: '"
100
0
90
.....
80
a: a:
.....
I0 I-
70 60 50 40 30 20 10
2
3
4
5
6
7
8
9
10
SUBJECT Fig. 4 - Total error scores for sub;ects one through ten from phoneme and word evaluations.
In summary, the results of this study suggested that: (1) phoneme difficulty but not phoneme position or grammatical word class significantly affected the errors of the apraxic speakers, and (2) the apraxic speakers were differentially affected by phoneme position and phoneme difficulty.
STUDY 2
The purpose of this study was to explore the relationship between the abstraction;level of words in noun, verb and adjective grammatical categories and the error productions of apraxic speakers on these words. -
-Material and method Twenty-five graduate students in speech pathology judged the abstractness of the 144 monosyllabic nouns, verbs and adjectives used for Study 1. Each judge was provided with specific directions regarding procedures to be followed in
24
]. M. Dunlop and T. P. Marquardt
making the ratings and a general discussion of the concept of word abstraction (Darley, Sherman and Siegel, 1959). After the instructions were read and questions about procedure answered, each judge worked at his/her own pace. A seven-point equal appearing interval scale was employed with one representing the least abstract and seven the most abstract word. Judging was completed in one session. A mean rating for each word was computed from the judges' ratings.
Results The means, standard deviations, and ranges of noun, verb, adjective and total abstraction ratings are presented in Table III. Examination of the table TABLE III
Means, Standard Deviations, and Ranges of Noun, Verb, Adjective, and Total Abstraction Ratings Qass Noun Verb Adjective Total
Mean
S.D.
Range
2.59 3.47 4.22 3.42
1.92 .96 1.03 1.25
1.08 - 5.72 1.88 - 5.52 1.80 - 6.08 1.08 - 6.08
reveals that there were apparent differences in abstraction level between the categories even though the words were matched for frequency of occurrence· Nouns were the least abstract (Mean = 2.59) followed by verbs (Mean = 3.47) and adjectives (Mean 4.22). Analysis of variance revealed that the categories differed significantly in abstraction level (F = 27.99; d.f. 2, 14; P < .0001): A t-test for Differences Among Several Means (Bruning and Kintz, 1968) revealed that each grammatical class mean differed significantly from the other means (p < .001) for each of the three comparisons: nouns vs. verbs; verbs vs. adjectives; nouns vs. adjectives. Interestingly, it was noted in Study 1 that errors of the apraxic speakers on these words were arranged in the same sequential order by mean number of errors (i.e., nouns, verbs, adjectives) although the error means were not significantly different for the three grammatical categories. The mean abstraction ratings of the words within each grammatical category were correlated with the errors made by the ten apraxic speakers during production of these words. Pearson Product Moment Correlation Coefficients for the noun, verb, adjective and total abstraction ratings and errors from the phoneme and word evaluations are presented in Table IV. Results revealed a significant positive correlation for nouns from the phoneme (r = .39, p < .01) and word (r = .31, P < .05) evaluations. Correlations
=
25
Word production in apraxia of speech TABLE IV
Correlations between Noun, Verb, Ad;ective, and Total Mean Abstraction Ratings and Errors from Phoneme and Word Evaluations Class
Evaluation
r
p
Noun
Phoneme Word
.39 .31
.01 .05
Verb
Phoneme Word
.35
.27
.05 n.s.
Adjective
Phoneme Word
-.04 .10
n.s. n.s.
Total
Phoneme Word
.28
.25
.01 .01
for verbs were significant for the phoneme evaluation (r = .35, p < .05) but not the word evaluation (r = .27, P > .05). Adjective correlations were not significant from the phoneme (r = ~ .04, p> .05) or word (r = .10, p> .05) evaluations. Correlations between mean errors and abstraction ratings for all words were significant for both phoneme (r = .25, P < .01) and word evaluations (r = .28, P < .01). Therefore, it can be concluded that: (1) correlations between apraxic errors and word abstractness ratings decrease as the abstractness of the grammatical class increases, and (2) a low, albeit significant, positive correlation exists between apraxic error scores and single word abstraction ratings.
DISCUSSION
The results of these studies suggested that: (1) phoneme difficulty but not phoneme position or grammatical word class affects the speech production skills of apraxic speakers, (2) apraxic speakers vary substantially from one another in their responses to phoneme position and phoneme difficulty, (3) apraxic errors on words are significantly related to word abstractness, and (4) the correlation between apraxic errors and word abstraction decreases with increases in grammatical class abstraction ratings.
Phoneme difficulty The finding that apraxic speakers make more errors on difficult phonemes and words containing these phonemes than during production .of easy phonemes or words containing these phonemes is not surprising in light of similar findings (Shankweiler and Harris, 1966; Johns and Darley, 1970; Deal and Darley, 1972). Moreover, the phonemes found to be most difficult
26
]. M. Dunlop and T. P. Marquardt
to produce U9/, /z/, Iti/) have previously been noted (Shankweiler and Harris, 1966; Johns and Darley, 1970). Although the /9/ consistently has been found to be the most difficult for apraxic speakers to produce, agreement as to the order of difficulty of phonemes has not been established. Differences in difficulty findings may lie in the particular words chosen for stimuli and the type of presentation mode utilized. Results of this study suggested that apraxic individuals demonstrated wide variations in performance in response to phoneme difficulty. Interestingly, the most severely involved apraxic speakers found all test phonemes to be difficult to produce. Mildly involved subject demonstrated a minimal increase in errors for difficult phonemes. Consequently, difficulty did not have a substantial effect on the error scores of these speakers. However, moderately involved subjects consistently showed a marked increase in error scores with difficulty from the phoneme and word evaluations. Phoneme position
The importance of phoneme position on error productions of apraxic speakers has not been established. Several investigators (Shankweiler and Harris, 1966; Trost and Canter, 1974) suggested that phonemes in the initial part of a word are most difficult for apraxic speakers to produce while other investigators (LaPointe and Johns, 1975) have reported no significant differences between the error scores of phonemes produced in the initial, medial and final position. LaPointe and Johns (1975) suggested that the inclusion of initiation errors as phonome errors could bias results. However, the results of this study would support their findings without consideration of this possible bias. Grammatical class and word abstraction
Results of previous studies (Deal and Darley, 1972; Martin and Rigrodsky, 1974) suggested that apraxia may be influenced by linguistic factors. The non-significant effects of grammatical class would not support this observation, although the positive significant correlation between single word abstraction ratings and errors would support such a contention. Consequently, these somewhat contradictory findings will be considered individually. Deal and Darley (1972) found that grammatical class may significantly affect apraxic errors for words greater than five phonemes in length. Grammatical class also was found to be significant when combined with difficult phonemes. The discrepancy between these findings and the results of this study may be explained by the difference in stimuli and presentation procedures used. Words chosen for this study were five phonemes or less in length and monosyllabic and accordingly may not have presented the same
Word production in apraxia
0/
speech
27
speech production difficulties as would have longer words. Secondly, since subject performance scores in the Deal and Darley (1972) study were based on an oral reading task, it is questionable whether these findings can be equated to the more spontaneous productions of the subjects from this study because a reading task allows for visual feedback and additional processing time. Therefore, a significant effect due to grammatical class may exist, although it was not demontrated from the results of this portion of the study. Several aspects of the correlation analyses bear further comment-Word abstraction ratings were positively and significantly correlated with the errors made by apraxic speakers on these words. Additionally, for word grammatical categories with significantly different mean abstraction ratings, correlations decreased as the abstraction rating of the category increased. One obvious interpretation might be that the semantic component and factors such as word type and abstraction level are related to the apraxic speaker's ability to produce words, especially less abstract words. This interpretation would suggest that apraxia is integrally related to other aspeots of language, since if it were simply a disorder 6f motor programming, the semantic component would not be significantly related to error frequency . Although such a relationship has been postulated by Martin and Rigrodsky (1974), several aspects of the data from this study must be explored further before it can be used to support such a hypothesis. First, it is possible that the apraxic speakers demonstrated a co-existing aphasic disorder. Incidence studies by Wertz, Rosenbek and Deal (1970), for example, revealed that approximately 65 percent of the adult cases they reviewed demonstrated apraxia complicated by aphasia. Moreover, Trost and Canter (1974) suggested that apraxia of speech frequently is seen as an element of an aphasic symptom complex and noted that Alajouanine, Ombredane and Durand (1939) and Alajouanine and Lhermitte (1960, 1963) emphasized that apraxia is often a residual disorder of a broader aphasic syndrome due to brain damage. Although the selection procedure for this study (correct responses to ten items from the Revised T oken Test) attempted to exclude subjects with higher-order aphasia, individuals with "pure" forms of the disorder are rare. Consequently, a low, albeit, significant correlation might be expected between the semantic content of words and error scores of apraxic speakers due to the effects of a minimal residual aphasia. Such a relationship between abstraction and word production has · been noted previously for aphasic patients (Spreen, 1968). Second, only one error was recorded for each word produced incorrectly by the apraxic subjects. Obviously, it was possible for the subjects to prolong a syllable, substitute a phoneme and distort yet another phoneme within the same word. Recording a single error per word may not have
28
]. M. Dunlop and T. P. Marquardt
provided an accurate estimate of the difficulty encountered by the subjects. Perhaps quantifying all errors would have provided a more valid estimate of the relationship between semantic component and apraxic error scores. However, this would require the development of non-overlapping categories for error and an assumption that the frequency of errors is related directly to the severity of the disorder. Third, no attempt was made to systematically quantify the types of errors of the apraxic subjects. If errors had been qualitatively categorized as phonemic (substitutions) or programming (repetitions, unintelligible responses, prolongations, etc.) and only phonemic errors were correlated with word abstraction the relationship between apraxia and word abstraction may have been more apparent. Interestingly, Trost and Canter (1974) suggested such an approach when they categorized some of the errors of patients with Broca's aphasia as phonemic and others as "inadequate responses." The investigators indicated that the inadequate responses (perseverative responses, paraphasic responses, recurrent utterances, random phonemes, no response) were not comparable to or analyzable as phonological errors. The difficulty with dichotomizing errors in this fashion is that some aspects of the disorder are subjected to intensive study, e.g. distinctive feature analyses of substitution errors, while the disrupted processes of speech motor programming characterized by non-phonemic errors (prolongations, distortions, perseverative responses, etc.) are neglected. If the errors of the apraxic speakers in this study had been dichotomized as phonemic and non-phonemic and only the phonemic errors were correlated with abstraction level, the relationship between these variables may have been more pronounced. In conclusion, the finding of a positive correlation between word abstraction and errors of apraxic speakers suggests that language deficits may be associated with the disorder. Accordingly, these results would lend some support to the hypothesis of Martin and Rigrodsky (1974) that there is no discrete separation between speech motor programming and other aspects of language. These results must be viewed cautiously, however, in light of our suggestion that the type and power of the observed relationship may be affected by the type of error analysis and subject selection procedures. Additional studies of the characteristics of apraxia and its relationship to other language processes appear in order, however, and we are currently investigating the effects of voice, abstraction, and noun phrase position on speech production in patients with apraxia. Finally, we would like to indicate that in-depth case studies and intensive investigations of phonemic and non-phonemic aspects of the disorder are crucial to our understanding of apraxia. The time has come to bring to bear our knowledge of psycholinguistics and speech motor programming to answer questions regarding this disorder.
Word production in apraxia of speech
29
SUMMARY
The errors of ten apraxic speakers on a single word task were analyzed to the effects of articulatory and linguistic variables on speech production. Results su~ested that phoneme difficulty but not phoneme position or grammatical class signifiCdntly affected the errors of the subjects. A significant low positive correlation between mean word abstraction and· the errors of the apraxic speakers was observed although correlations for the grammatical classes decreased with increases in ab:.traction. These findings were interpreted to suggest that impaired motor speech ptl1gramming may be affected by linguistic and articulatory variables.
determin~
Acknowledgmi!nt. The authors acknowledge the help of Robert Dunlop in the preparation of figures for this article.
REFERENCES ALAJOUANINE, T., OMBREDANE, A., and DURAND, M. (1939) Le Syndrome de Desintegration Phonetique dans l'Aphasie, Masson, P:u:is. - , and LHERMITTE, F. (1960) Les troubles des activites expressives du langage dans l'aphasie: Leurs relations avec les apraxies, "Revue Neurologique," 102, 604-629. , - (1963) Activites expressives du langage dans l'aphasie, "Encephale," 52, 5-45. ATEN, J. L., JOHNS, D. F., and DARLEY, F. L. (1971) Auditory perception of sequenced words in apraxia of speech, "J. Speech Hear. Res.," 14, 131-143. - , DARLEY, F. L., DEAL, J. L., and JOHNS, D. F. (1975) Comment on A. D. Martin's Some objections to the term apraxia of speech, "J. Speech Hear. Dis.," 40, 416-420. BRUNING, ]., and KINTZ, B. (1968) Computational Handbook of Statistics, Scotts, Foresman and Co., Glenview. CARROLL, J. B., DAVIES, P., and RICKMAN, B. (1971) Word Frequency Book, American Heritage Publishing Co., Inc., New York. DARLEY, F. L., SHERMAN, D., and SIEGAL, G. M. (1959) Scaling of abstraction level of single words, "J. Speech Hear. Res.," 2, 161-167. DEAL, ]. L., and DARLEY, F. L. (1972) The influence of linguistic and situational variables on phonemic accuracy in apraxia of speech, "J. Speech He:u:. Res.," 15, 639-653. JOHNS, D. F., and DARLEY, F. L. (1970) Phonemic variability in apraxia of speech, "J. Speech Hear. Res.," 14, 131-143. LAPOINTE, L. L., and JOHNS, D. F. (1975) Some phonemic characteristics in apraxia of speech, "J. Commun. Dis.," 8, 259-269. MARTIN, A. D. (1974) Some objections to the term "apraxia of speech," "J. Speech Hear. Dis.," 39, 53-64. - , and RIGRODSKY, S. (1974) Phonological impairment in aphasia, Part I, "Cortex," 10, 317-328. McNEIL, M. R. (1973) A psychometric revision of the Token Test, Paper presented at the American Speech and He:u:ing Association Convention, Detroit, Michigan. ROSENBEK, J. c., WERTZ, R. T., and DARLEY, F. L. (1973) Oral sensation and perception in apraxia of speech and aphasia, "J. Speech Hear. Res.," 16, 22-36. SHANKWEILER, D., and HARRIS, K. (1966) An experimental approach to the problem of articulation in aphasics, "Cortex," 2, 277-292. SPREEN, O. (1968) Psycholinguistic aspects of aphasia, "J. Speech He:u:. Res.," 11, 467-480. THORNDIKE, E. L., and LoRGE, 1. (1944) Teachers Word Book of 30,000 Words, Teachers College Press, New York. TROST, J. E., and CANTER, G. J. (1974) Apraxia of speech in patients with Broca's aphasia: A study of phoneme production accuracy and error patterns, "Brain Lang.," 1, 63-79. WERTZ, R. T., ROSENBEK, J. C., and DEAL, J. L. (1970) A review of 228 cases of apraxia of speech: Classification, etiology and localization, Paper presened at the American Speech and Hearing Association Convention, New York. Jeanette M. Dunlop, M. A., Instructor, Department of Audiology and Speech Pathology, University of Tennessee, Knoxville, Tennessee 37916. Thomas P. Marquardt, Ph. D., Assistant Professor, Department of Audiology and Speech Pathology, University of Tennessee, Knoxville, Tennessee 37916.
INTRODUCTION
For more than a century investigators have been unable to agree whether apraxia of speech is a motor programming disorder devoid of linguistic components or a phonological disorder without a discrete separation from other language processes. Most recent investigations (Johns and Darley, 1970; Aten, Johns and Darley, 1971; Deal and Darley, 1972; Rosenbek, Wertz and Darley, 1973; LaPointe and Johns, 1975) have described apraxia as a non-linguistic motor programming disorder without significant speech musculature weakness, slowness, or incoordination. However, Martin and Rigrodsky {197 4) found that a group of aphasics with phonological impairments made more phoneme errors when they were asked to repeat meaningless stimuli rather than meaningful stimuli and concluded that the semantic component of words may significantly aid in the motor production of phonemes. Martin (1974) hypothesized that" ... the influence of other linguistic variables on phonological production demonstrates that there is not a discrete separation of motor acts from other language processes. or their possible impairment." He suggested further that the repetitions, blocks and groping behaviors of apraxics toward correct production were similar to other aphasic behaviors clearly showing difficulty in processing of linguistic units. In response, Aten, Darley, Deal and Johns (1975) indicated that defining apraxia as a motor programming disorder not primarily due to impairment of sensory, intellectual or higher language functioning: " ... does not assert that speech and language are unrelated or that phonological impairment is wholly uninfluenced by language functioning, but it does suggest that programming of phoneme production can be selectively impaired without impairment of language functioning." , A portion of this research was presented at the Convention of the AmeriCan Speech and Hearing Association, Washington, D.C., 1975. Preparation of this manuscript was supported, in part, by the University of Tennessee Neuropathology Services Program. l.nrtf'Y I1CJ77\
n
17.,Q
18
]. M . Dunlop and T. P. Marquardt
The hypothesized link between linguistic processes and apraxia of speech, however, has not been adequately explored. The purposes of this research were: (1) to investigate the effects of grammatical word class, phoneme position, and phoneme difficulty on the errors of apraxic speakers, and (2) to determine the relationship between word abstraction and the errors of apraxic speakers on monosyllabic words.
STUDY
1
Material and method Subjects
Ten adults, with a history of left cortical damage and articulatory characteristics indicative of apraxia of speech (LaPointe and Johns, 1975), served as subjects (Table I). TABLE I
Age, Sex, Etiology of Brain Damage, and Duration Since Onset of Symptoms for Sub;ects with Apraxia of Speech (CV A = cerebrovascular accident)
Subject
1 2 3
4 5 6 7 8 9 10
Age (years)
Sex
Etiology
Duration (months)
61 69 50 55' 55 57 57 29 42 60
F F
eVA eVA eVA eVA eVA eVA eVA Head injury eVA eVA
18 27 17 12 10
M M M M M M
F F
3 8
26 4 80
Each subject demonstrated hearing acuity within normal1imits at 500, 1000 ancl2000 Hz (ISO) in the better ear, no significant auditory comprehension difficulties as measured by their ability to respond correctly to ten items (two items each fromSubtests I, II, III and IV and one item each from Subtests V and VI) selected from the Revised Token Test (McNeil, 1973), auditory comprehension skills superior to oral expression, and no history of dementia, previous speech problems, or retardation. The subjects were native speakers of English and at least three months post brain trauma. They ranged in age from 29 to 69 years with a mean age of 53.5 years.
Word production in apraxia of spe~ch
19
Stimuli
Stimuli were 144 monosyllabic words divided into two Lists of 72 words each. List I contained equal numbers of nouns, verbs and adjectives each of which included one of six phonemes (/v/, Izl, lSI, ItSI, Id3/, Ie/) judged to be difficult for apraxic speakers to produce (Shankweiler and. Harris, 1966; Johns and Darley, 1970). Each of the six phonemes appeared in either the initial or final position of the stimulus word. Therefore, each grammatical category contained a test phoneme in four words, two with the selected phoneme in the initial position and two with the phoneme in the final position. List II was constructed similarly but contained six phonemes (/t/, Idl, Ibl, IkJ, Ip/, In/) judged to be easy for apraxic speakers to produce (Johns and Darley, 1970). Fotty of the stimulus words were used in more than one grammatical category (i.e., march - verb; march - noun). Four two syllable words were included in the Lists due to difficulty in meeting criteria for grammatical category. All words had frequencies of occurrence ofapproxima.tely 50 in a million words according to the Thorndike-Lorge List (1944) and the Carroll, Davies and Rickman List (1971).
Procedures
The words from Lists I and II were randomized and then presented to the subjects. Each word was included at or near the end of a sentence constructed of five or less words. Each sentence was presented twice. For the first presentation the sentence was read in its entirety; during the second presentation the stimulus word was omitted. The subject's task was to orally produce the omitted word. Responses were tape-recorded for later analysis.
Analysis
Each test word produced by the apraxic subjects was judged twice. First, for correct production of the test phoneme and second for correct production of the entire word. Phonemes were judged to be in error if they were: (1) distorted, (2) repeated, (3) omitted, (4) self-corrected, (5) prolonged, (6) substituted for, (7) unintelligible, (8) included within a blend. Production of the word was considered incorrect if any of the following were noted: ( 1) phoneme repetition, (2) word repetition, (3) phoneme addition, (4) phoneme substitution, (5) self-correction, (6) pause before or within the word, (7) phoneme prolongation, (8) phoneme omission, (9) phoneme distortion, (10) unintelligible response or no response (Deal and Darley, 1972). Although more than one of the categories for production errors could be recorded for a subject's response, only one possible error per phoneme or word was tabulated for statistical analysis.
Reliability
Agreement ratios were computed for phoneme and word evaluations by utilizing the formula:
]. M. Dunlop and T. P. Marquardt
20
·l· ReIiabIlty =
Agreements -,--Agreements + Differences .
Intrajudge reliability for five of the tape-recorded samples re-judged by the investigator two weeks following the initial judging was .89 for the phoneme evaluation and .90 for the word evaluation. Interjudge reliability, determined from analysis of the same five tapes by a graduate student in speech pathology, was .83 for the phoneme evaluation and .85 for the word evaluation.
Results
Error scores were tabulated for each of the apraxic subjects. Means, standard deviations, and ranges for difficulty, position and grammatical class error scores from the phoneme and word evaluations are presented in Table II. TABLE II
Means, Standard Deviations, and Ranges of Error Scores for Position, Difficulty, and Grammatical Class from Phoneme and Word Evaluations Evaluation
Variable
PhonelIle
Position Difficulty Class
Word
Position Difficulty Class
Initial Final Easy Difficult Noun Verb Adjective Initial Final Easy Difficult Noun Verb Adjective
Mean
S.D.
Range
30.6 31.2 24.5 37.3 19.7 20.6 21.5 40.3 41.5 36.7 45.1 25.4 27.1 29.3
24.6 28.6 25.8 26.0 18.8 17.9 16.8 24.4 24.8 24.8 23.7 17.3 16.6 15.3
9-69 4-72 5-69 7-72 3-48 4-47 4-47 13-72 11-72 9-72 13-72 7-48 9-48 5-48
A Treatment X Treatment X Treatment X Subjects analysis of variance was utilized to evaluate the effects of these variables on the error scores of the apraxic subjects. Difficulty
The effects of difficulty were significant for both the phomene (F = 12.783; d.f. 1, 9; P < .01) and word (F = 6.720; d.£. 1, 9; P < .05)
Word production in. apraxia 01 speech
21
evaluations. These results suggest that it was easier for the subjects to produce .. easy" phonemes or words containing these phonemes than "difficult" phonemes or words containing "difficult" phonemes (Figure 1). Mean error •
o
50
EASY
DIFFICULT
45 40 CI)
a::
0
a: a:
35 30
.....
25
"".....
20
<{
:;:
15 10 5
0
Fig. 1 -
PHONEME
WORD
Easy and difficult phoneme mean error scores from phoneme and word evaluations.
scores for the "easy" phonemes were 24.5 for the phoneme evaluation and 36.7 for the word evaluation. Mean error scores for the" difficult" phonemes were 37.3 for the phoneme evaluation and 45.1 for the word evaluation.
Position Position was not found to be a significant factor in either the phoneme (F = .032; d.£. 1, 9; p> .05) or word evaluation (F = 0401; d.£. 1, 9; P > .05). Examination of Figure 2 reveals that the mean errors for the initial and final position were almost identical; 30.,6 vs. 31.2 for the phoneme •
••
o
••
PHONEME Fig. 2 -
INITIAL FINAL
WORD
Initial and final position mean error scores from phoneme and word evaluations.
22
]. M. DunlopandT. P. Marquardt
evaluation and 40.3 vs. 41.5 for the. word evaluation. Apparently, the position of the phoneme did not significantly affect the errors of the apraxic speakers. Grammatical class
Class was not found to be significant from either ' the phoneme (F = 2.218; d.f. 2, 18, P > .05) or word evaluation (F = 3.370 ; d.f. 2, 18; p> .05). However, examination of Figure 3 reveals a trend in which the subjects produced the least errors on nouns followed by verbs and then
'"
a:
50
o
45
f:a VERBS
40
•
NOUNS ADJECTIVES
35
0
a: 30 a: u.o
25
Z
20
«
u.o
::iE
'1·5 10
:; 0
PHONEME Fig. 3 -
WORP '
Noun, verb and adiective mean error scores from phoneme and word evaluations.
adjectives. Error means were 19.7 for nouns, 20.6 for verbs and 21.5 for adjectives from the phoneme evaluation and 25.4 for nouns, 27.1 for verbs and 29 .3 for adjectives from the word evaluation. Interestingly, none of the interactions between difficulty, position and grammatical class were significant. Subjects
Substantial variability between the apraxic subjects selected for this study was noted. Examination of Figure 4 reveals that total errors from the phoneme evaluation ranged from 15 to 141 out of a possible 144, while total errors from the word evaluation ranged from 27 to 144. Additionally, interactions between the subjects and variables under study were noted. For example, from the phoneme evaluation, it was observed that six of the subjects found the final position more difficult than the initial position, while the other four subjects found the initial position more difficult than the final positibn. Similar interaction patterns between subjects and difficulty w~re noted. These
23
Word production in apraxia of speech
findings suggest that within group variability may contribute to the di$culty encountered in studying apraxic subjects. 150 140 130 120 110
a: '"
100
0
90
.....
80
a: a:
.....
I0 I-
70 60 50 40 30 20 10
2
3
4
5
6
7
8
9
10
SUBJECT Fig. 4 - Total error scores for sub;ects one through ten from phoneme and word evaluations.
In summary, the results of this study suggested that: (1) phoneme difficulty but not phoneme position or grammatical word class significantly affected the errors of the apraxic speakers, and (2) the apraxic speakers were differentially affected by phoneme position and phoneme difficulty.
STUDY 2
The purpose of this study was to explore the relationship between the abstraction;level of words in noun, verb and adjective grammatical categories and the error productions of apraxic speakers on these words. -
-Material and method Twenty-five graduate students in speech pathology judged the abstractness of the 144 monosyllabic nouns, verbs and adjectives used for Study 1. Each judge was provided with specific directions regarding procedures to be followed in
24
]. M. Dunlop and T. P. Marquardt
making the ratings and a general discussion of the concept of word abstraction (Darley, Sherman and Siegel, 1959). After the instructions were read and questions about procedure answered, each judge worked at his/her own pace. A seven-point equal appearing interval scale was employed with one representing the least abstract and seven the most abstract word. Judging was completed in one session. A mean rating for each word was computed from the judges' ratings.
Results The means, standard deviations, and ranges of noun, verb, adjective and total abstraction ratings are presented in Table III. Examination of the table TABLE III
Means, Standard Deviations, and Ranges of Noun, Verb, Adjective, and Total Abstraction Ratings Qass Noun Verb Adjective Total
Mean
S.D.
Range
2.59 3.47 4.22 3.42
1.92 .96 1.03 1.25
1.08 - 5.72 1.88 - 5.52 1.80 - 6.08 1.08 - 6.08
reveals that there were apparent differences in abstraction level between the categories even though the words were matched for frequency of occurrence· Nouns were the least abstract (Mean = 2.59) followed by verbs (Mean = 3.47) and adjectives (Mean 4.22). Analysis of variance revealed that the categories differed significantly in abstraction level (F = 27.99; d.f. 2, 14; P < .0001): A t-test for Differences Among Several Means (Bruning and Kintz, 1968) revealed that each grammatical class mean differed significantly from the other means (p < .001) for each of the three comparisons: nouns vs. verbs; verbs vs. adjectives; nouns vs. adjectives. Interestingly, it was noted in Study 1 that errors of the apraxic speakers on these words were arranged in the same sequential order by mean number of errors (i.e., nouns, verbs, adjectives) although the error means were not significantly different for the three grammatical categories. The mean abstraction ratings of the words within each grammatical category were correlated with the errors made by the ten apraxic speakers during production of these words. Pearson Product Moment Correlation Coefficients for the noun, verb, adjective and total abstraction ratings and errors from the phoneme and word evaluations are presented in Table IV. Results revealed a significant positive correlation for nouns from the phoneme (r = .39, p < .01) and word (r = .31, P < .05) evaluations. Correlations
=
25
Word production in apraxia of speech TABLE IV
Correlations between Noun, Verb, Ad;ective, and Total Mean Abstraction Ratings and Errors from Phoneme and Word Evaluations Class
Evaluation
r
p
Noun
Phoneme Word
.39 .31
.01 .05
Verb
Phoneme Word
.35
.27
.05 n.s.
Adjective
Phoneme Word
-.04 .10
n.s. n.s.
Total
Phoneme Word
.28
.25
.01 .01
for verbs were significant for the phoneme evaluation (r = .35, p < .05) but not the word evaluation (r = .27, P > .05). Adjective correlations were not significant from the phoneme (r = ~ .04, p> .05) or word (r = .10, p> .05) evaluations. Correlations between mean errors and abstraction ratings for all words were significant for both phoneme (r = .25, P < .01) and word evaluations (r = .28, P < .01). Therefore, it can be concluded that: (1) correlations between apraxic errors and word abstractness ratings decrease as the abstractness of the grammatical class increases, and (2) a low, albeit significant, positive correlation exists between apraxic error scores and single word abstraction ratings.
DISCUSSION
The results of these studies suggested that: (1) phoneme difficulty but not phoneme position or grammatical word class affects the speech production skills of apraxic speakers, (2) apraxic speakers vary substantially from one another in their responses to phoneme position and phoneme difficulty, (3) apraxic errors on words are significantly related to word abstractness, and (4) the correlation between apraxic errors and word abstraction decreases with increases in grammatical class abstraction ratings.
Phoneme difficulty The finding that apraxic speakers make more errors on difficult phonemes and words containing these phonemes than during production .of easy phonemes or words containing these phonemes is not surprising in light of similar findings (Shankweiler and Harris, 1966; Johns and Darley, 1970; Deal and Darley, 1972). Moreover, the phonemes found to be most difficult
26
]. M. Dunlop and T. P. Marquardt
to produce U9/, /z/, Iti/) have previously been noted (Shankweiler and Harris, 1966; Johns and Darley, 1970). Although the /9/ consistently has been found to be the most difficult for apraxic speakers to produce, agreement as to the order of difficulty of phonemes has not been established. Differences in difficulty findings may lie in the particular words chosen for stimuli and the type of presentation mode utilized. Results of this study suggested that apraxic individuals demonstrated wide variations in performance in response to phoneme difficulty. Interestingly, the most severely involved apraxic speakers found all test phonemes to be difficult to produce. Mildly involved subject demonstrated a minimal increase in errors for difficult phonemes. Consequently, difficulty did not have a substantial effect on the error scores of these speakers. However, moderately involved subjects consistently showed a marked increase in error scores with difficulty from the phoneme and word evaluations. Phoneme position
The importance of phoneme position on error productions of apraxic speakers has not been established. Several investigators (Shankweiler and Harris, 1966; Trost and Canter, 1974) suggested that phonemes in the initial part of a word are most difficult for apraxic speakers to produce while other investigators (LaPointe and Johns, 1975) have reported no significant differences between the error scores of phonemes produced in the initial, medial and final position. LaPointe and Johns (1975) suggested that the inclusion of initiation errors as phonome errors could bias results. However, the results of this study would support their findings without consideration of this possible bias. Grammatical class and word abstraction
Results of previous studies (Deal and Darley, 1972; Martin and Rigrodsky, 1974) suggested that apraxia may be influenced by linguistic factors. The non-significant effects of grammatical class would not support this observation, although the positive significant correlation between single word abstraction ratings and errors would support such a contention. Consequently, these somewhat contradictory findings will be considered individually. Deal and Darley (1972) found that grammatical class may significantly affect apraxic errors for words greater than five phonemes in length. Grammatical class also was found to be significant when combined with difficult phonemes. The discrepancy between these findings and the results of this study may be explained by the difference in stimuli and presentation procedures used. Words chosen for this study were five phonemes or less in length and monosyllabic and accordingly may not have presented the same
Word production in apraxia
0/
speech
27
speech production difficulties as would have longer words. Secondly, since subject performance scores in the Deal and Darley (1972) study were based on an oral reading task, it is questionable whether these findings can be equated to the more spontaneous productions of the subjects from this study because a reading task allows for visual feedback and additional processing time. Therefore, a significant effect due to grammatical class may exist, although it was not demontrated from the results of this portion of the study. Several aspects of the correlation analyses bear further comment-Word abstraction ratings were positively and significantly correlated with the errors made by apraxic speakers on these words. Additionally, for word grammatical categories with significantly different mean abstraction ratings, correlations decreased as the abstraction rating of the category increased. One obvious interpretation might be that the semantic component and factors such as word type and abstraction level are related to the apraxic speaker's ability to produce words, especially less abstract words. This interpretation would suggest that apraxia is integrally related to other aspeots of language, since if it were simply a disorder 6f motor programming, the semantic component would not be significantly related to error frequency . Although such a relationship has been postulated by Martin and Rigrodsky (1974), several aspects of the data from this study must be explored further before it can be used to support such a hypothesis. First, it is possible that the apraxic speakers demonstrated a co-existing aphasic disorder. Incidence studies by Wertz, Rosenbek and Deal (1970), for example, revealed that approximately 65 percent of the adult cases they reviewed demonstrated apraxia complicated by aphasia. Moreover, Trost and Canter (1974) suggested that apraxia of speech frequently is seen as an element of an aphasic symptom complex and noted that Alajouanine, Ombredane and Durand (1939) and Alajouanine and Lhermitte (1960, 1963) emphasized that apraxia is often a residual disorder of a broader aphasic syndrome due to brain damage. Although the selection procedure for this study (correct responses to ten items from the Revised T oken Test) attempted to exclude subjects with higher-order aphasia, individuals with "pure" forms of the disorder are rare. Consequently, a low, albeit, significant correlation might be expected between the semantic content of words and error scores of apraxic speakers due to the effects of a minimal residual aphasia. Such a relationship between abstraction and word production has · been noted previously for aphasic patients (Spreen, 1968). Second, only one error was recorded for each word produced incorrectly by the apraxic subjects. Obviously, it was possible for the subjects to prolong a syllable, substitute a phoneme and distort yet another phoneme within the same word. Recording a single error per word may not have
28
]. M. Dunlop and T. P. Marquardt
provided an accurate estimate of the difficulty encountered by the subjects. Perhaps quantifying all errors would have provided a more valid estimate of the relationship between semantic component and apraxic error scores. However, this would require the development of non-overlapping categories for error and an assumption that the frequency of errors is related directly to the severity of the disorder. Third, no attempt was made to systematically quantify the types of errors of the apraxic subjects. If errors had been qualitatively categorized as phonemic (substitutions) or programming (repetitions, unintelligible responses, prolongations, etc.) and only phonemic errors were correlated with word abstraction the relationship between apraxia and word abstraction may have been more apparent. Interestingly, Trost and Canter (1974) suggested such an approach when they categorized some of the errors of patients with Broca's aphasia as phonemic and others as "inadequate responses." The investigators indicated that the inadequate responses (perseverative responses, paraphasic responses, recurrent utterances, random phonemes, no response) were not comparable to or analyzable as phonological errors. The difficulty with dichotomizing errors in this fashion is that some aspects of the disorder are subjected to intensive study, e.g. distinctive feature analyses of substitution errors, while the disrupted processes of speech motor programming characterized by non-phonemic errors (prolongations, distortions, perseverative responses, etc.) are neglected. If the errors of the apraxic speakers in this study had been dichotomized as phonemic and non-phonemic and only the phonemic errors were correlated with abstraction level, the relationship between these variables may have been more pronounced. In conclusion, the finding of a positive correlation between word abstraction and errors of apraxic speakers suggests that language deficits may be associated with the disorder. Accordingly, these results would lend some support to the hypothesis of Martin and Rigrodsky (1974) that there is no discrete separation between speech motor programming and other aspects of language. These results must be viewed cautiously, however, in light of our suggestion that the type and power of the observed relationship may be affected by the type of error analysis and subject selection procedures. Additional studies of the characteristics of apraxia and its relationship to other language processes appear in order, however, and we are currently investigating the effects of voice, abstraction, and noun phrase position on speech production in patients with apraxia. Finally, we would like to indicate that in-depth case studies and intensive investigations of phonemic and non-phonemic aspects of the disorder are crucial to our understanding of apraxia. The time has come to bring to bear our knowledge of psycholinguistics and speech motor programming to answer questions regarding this disorder.
Word production in apraxia of speech
29
SUMMARY
The errors of ten apraxic speakers on a single word task were analyzed to the effects of articulatory and linguistic variables on speech production. Results su~ested that phoneme difficulty but not phoneme position or grammatical class signifiCdntly affected the errors of the subjects. A significant low positive correlation between mean word abstraction and· the errors of the apraxic speakers was observed although correlations for the grammatical classes decreased with increases in ab:.traction. These findings were interpreted to suggest that impaired motor speech ptl1gramming may be affected by linguistic and articulatory variables.
determin~
Acknowledgmi!nt. The authors acknowledge the help of Robert Dunlop in the preparation of figures for this article.
REFERENCES ALAJOUANINE, T., OMBREDANE, A., and DURAND, M. (1939) Le Syndrome de Desintegration Phonetique dans l'Aphasie, Masson, P:u:is. - , and LHERMITTE, F. (1960) Les troubles des activites expressives du langage dans l'aphasie: Leurs relations avec les apraxies, "Revue Neurologique," 102, 604-629. , - (1963) Activites expressives du langage dans l'aphasie, "Encephale," 52, 5-45. ATEN, J. L., JOHNS, D. F., and DARLEY, F. L. (1971) Auditory perception of sequenced words in apraxia of speech, "J. Speech Hear. Res.," 14, 131-143. - , DARLEY, F. L., DEAL, J. L., and JOHNS, D. F. (1975) Comment on A. D. Martin's Some objections to the term apraxia of speech, "J. Speech Hear. Dis.," 40, 416-420. BRUNING, ]., and KINTZ, B. (1968) Computational Handbook of Statistics, Scotts, Foresman and Co., Glenview. CARROLL, J. B., DAVIES, P., and RICKMAN, B. (1971) Word Frequency Book, American Heritage Publishing Co., Inc., New York. DARLEY, F. L., SHERMAN, D., and SIEGAL, G. M. (1959) Scaling of abstraction level of single words, "J. Speech Hear. Res.," 2, 161-167. DEAL, ]. L., and DARLEY, F. L. (1972) The influence of linguistic and situational variables on phonemic accuracy in apraxia of speech, "J. Speech He:u:. Res.," 15, 639-653. JOHNS, D. F., and DARLEY, F. L. (1970) Phonemic variability in apraxia of speech, "J. Speech Hear. Res.," 14, 131-143. LAPOINTE, L. L., and JOHNS, D. F. (1975) Some phonemic characteristics in apraxia of speech, "J. Commun. Dis.," 8, 259-269. MARTIN, A. D. (1974) Some objections to the term "apraxia of speech," "J. Speech Hear. Dis.," 39, 53-64. - , and RIGRODSKY, S. (1974) Phonological impairment in aphasia, Part I, "Cortex," 10, 317-328. McNEIL, M. R. (1973) A psychometric revision of the Token Test, Paper presented at the American Speech and He:u:ing Association Convention, Detroit, Michigan. ROSENBEK, J. c., WERTZ, R. T., and DARLEY, F. L. (1973) Oral sensation and perception in apraxia of speech and aphasia, "J. Speech Hear. Res.," 16, 22-36. SHANKWEILER, D., and HARRIS, K. (1966) An experimental approach to the problem of articulation in aphasics, "Cortex," 2, 277-292. SPREEN, O. (1968) Psycholinguistic aspects of aphasia, "J. Speech He:u:. Res.," 11, 467-480. THORNDIKE, E. L., and LoRGE, 1. (1944) Teachers Word Book of 30,000 Words, Teachers College Press, New York. TROST, J. E., and CANTER, G. J. (1974) Apraxia of speech in patients with Broca's aphasia: A study of phoneme production accuracy and error patterns, "Brain Lang.," 1, 63-79. WERTZ, R. T., ROSENBEK, J. C., and DEAL, J. L. (1970) A review of 228 cases of apraxia of speech: Classification, etiology and localization, Paper presened at the American Speech and Hearing Association Convention, New York. Jeanette M. Dunlop, M. A., Instructor, Department of Audiology and Speech Pathology, University of Tennessee, Knoxville, Tennessee 37916. Thomas P. Marquardt, Ph. D., Assistant Professor, Department of Audiology and Speech Pathology, University of Tennessee, Knoxville, Tennessee 37916.