Feature analysis and the token test

BRAIN

AND

LANGUAGE

10,

98-l 10 (1980)

Feature Analysis and the Token Test ANNETTE Schweizerische

K.

BIRCHMEIER

Pflegerinnenschule

In a picture-matching task pictures of objects had to be arranged into pairs by aphasic and nonaphasic patients and normal controls. Aphasic patients were also given the Token Test. Correlation between the rank order of error scores in both tests was highly significant in aphasic patients. The pictures were also given to a normal group for free matching. Overlapping of normal performance on free matching and aphasic performance on bound matching occurred. We hypothesized that aphasic impairment was due to a dimculty in calling up associations, difficulty in feature analysis, and in moving from one concept to another. These findings are discussed in the light of abilities needed for Token Test performance. The results indicate that the traditionally presumed fundamental difference between verbal and nonverbal cognitive tasks is rather unsatisfactory.

In 1870 Finkelnburg described five cases of “asymbolia” and thereby initiated the discussion on nonverbal deficits in aphasia. His patients had difficulties with gestures and pantomime, one had acalculia, and another amusia. Finkelnburg realized that understanding and handling of nonverbal systems of signs were disturbed in these cases. Fifty-four years later Goldstein (1924) published results of an investigation of aphasic impairments in naming colors, identifying colors by their names, associating colors to objects and sorting colors according to principal hue (light green/dark green = green). They tended to disregard hue and to base their choice on brightness and saturation instead. Goldstein argued that aphasics had not retained well-defined concepts and that their ability for analytical thinking was impaired. About 35 years later De Renzi and Vignolo (1962) built the Token Test (TT) on these findings and on auditory I should like to thank Professor F. Lhermitte, Paris, for the generous permission to do the experimental part of this study at his clinic, and his speech therapists for their cooperative spirit. I think with gratitude of the 16 aphasic patients who kindly assisted a stranger and carefully performed in what seemed so difficult and puzzling a task. Professor G. Forster and the board of the Schweizerische Pflegerinnenschule, Zurich, encouraged this study and supported it in part by a grant from the clinic’s private funds. Address reprint requests to Annette K. Birchmeier, Schwerzenbachstrasse 18, CH-8117 F%llanden, Switzerland. 98 0093-934X/80/030098-13$02.00/0 Copyright All rights

@ 1980 by Academic Press, Inc. of reproduction in any form reserved.

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verbal comprehension. Ever since clinicians have been impressed by the diagnostic efficiency of the T”T while researchers have been puzzled by the fact that nonfluent aphasics had as much difficulty with it as fluent aphasics. The test was supposed to’ tap verbal comprehension, yet there were some doubts as to whether it really tested the same capacities in all aphasics. Much research went into evaluating the sensitivity and into determining the ideal cut-off score for distinguishing aphasic from nonaphasic patients (Boller & Vignolo, 1966; Orgass & Poeck, 1966; Hartje, Kerschensteiner, Poeck, & Orgass, 1973; Swisher & Sarno, 1969). At the same time it was established that the test gave a reliable evaluation of the overall severity of aphasic impairment (Orgass & Poeck, 1969). As the test was rather long for some patients, several short versions were proposed. They proved nearly as efficient as the original test (Spellacy & Spreen, 1969; Sipos & Tlgert, 1972; Orgass, Poeck, Hartje, & Kerschensteiner, 1973; De Renzi & Faglioni, 1978). Another group of studies drew attention to linguistic variables in the TT (Whitaker & Noll, 1972, Poeck, Orgass, Kerschensteiner, & Hartje, 1974; Lesser, 1974). They were all based on the final section. In that part the ability to understand the exact implication of each grammatical form is challenged much more than in the preceding parts. Aphasics were found to have difficulties with the handling of overt and implicit instrumental case (implicit: “Touch the blue circle and the red rectangle”; overt: “Touch the blue circle with the red rectangle”) but their difficulties were even greater with short reversible active subject/verb/object sentences where sequencing of words was critical to their interpretation. In view of the nonverbal color impairment first noticed by Lewandowsky (1908) it was felt quite from the start that some very general variable might possibly be implied in TT performance. This hypothesis was strengthened when it was found that nonverbal impairments of aphasic patients correlated well with TT scores. Basso, Faglioni, and Spinnler (1976) confirmed this for nonverbal color impairments. But patients were also found to have difficulties with analyzing meaningful sounds and associating them with the proper objects (Faglioni, Spinnler, & Vignolo, 1969; Doehring, Dudley, & Coderre, 1967; Strohner, Cohen, Kelter, & Woll, 1978); they also had difficulties in deciding which of two pictures in an item was indicated by a third when the mediator was a common perceptual feature (swan-turkey: snowman; mediator: white) (Kelter, Cohen, Engel, List, & Strohner, 1976). In the last study TT correlations were not given but patients were carefully matched and no difference found between fluent and nonfluent aphasics. Several interpretations for all these findings seem possible. If the TT is considered a purely verbal test and association tasks as unconnected with linguistic abilities, similar findings or high correlation would be interpreted as indicating a general nonverbal associative deficit concomitant with aphasia. As TT scores are a reliable measure of severity of aphasic

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impairment high correlation with TT scores might be due to impairment of a basic conceptual structure underlying language. On the other hand, one might argue that aphasics’ lack of covert verbal mediation (Goodglass, Denes, & Calderon, 1974) was a handicap in associative tasks and that availability of verbal cues was a prerequisite for verbal as well as for nonverbal material. Association would then be supposed to rely to some extent on semantic feature analysis and the ability of singling out particular features. In the study by Kelter et al. (1976) aphasics were not significantly impaired when pictorial association was based on contextual links. The absence of contextual links in the TT might therefore make semantic analysis particularly difficult for aphasics. We do not know how consciousness and availability of an object’s name and its inherent semantic information influences our awareness of that object. In a small study on color perception and color associations of Arab nomads (Zollinger & Benhar, 1974), nomads were found to have no difficulty in recognizing and naming different colors. But when asked about the color of a camel, the answers included green, blue, yellow, and red as well as white, brown, skin-colored, and black. The only color that was not mentioned was purple. Obviously the natural color of a camel was no distinctive feature for a camel among these nomads. Color names could therefore be applied to express other aspects of meaning pertaining to human experience of colors. Thus the designation of a particular color can be seen as one of several aspects of meaning in a color name. EXPERIMENTAL

DATA

With the intention of finding another general property comparable to “color” which might prove difficult for aphasics and with the wish of better understanding their associative performances, a matching task based on “material” was devised. It consisted of three series of 12 pictures each which had to be arranged into pairs according to the material the depicted objects were made of. The pictures were color photographs cut out of good magazines and mounted on cardboard (each card 4 x 4 in. in size). Two objects of the same material which formed a pair were chosen in a way to exclude as carefully as possible other associative links, so that the right choice had to be based on identity of material. First a mixed group of 20 normal subjects was tested. They made no mistakes. We therefore concluded that the task was easy and the pictures unequivocal. Next a group of 16 patients with a great variety of syndromes but a fairly even level of education and no considerable visual handicaps (age: 19-76 years, average: 55.8 years) had to assort the same pictures. Great care was taken to ensure that all patients had well understood what they were expected to do and were warned of possible errors. First the material quality of things was demonstrated with the help of objects in

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the room (e.g., “Some things are made of glass. In this room the lamp is made of glass, and so are the window-panes. They are both made of glass.“). When the patient indicated that he had understood, a series of eight pictures was used for exercise. Four pictures were laid out on the table; the four response pictures were handed over in a fixed but random order. The patients were asked to form pairs as shown. The first two pairs (from left to right) were assorted correctly by 14 out of 16 patients. All patients began with these two pairs. Their performance significantly differed from chance performance (p < .OOl). One patient assorted the second and the third, one patient the second and the fourth pairs correctlv. When a patient hesitated to begin, he was shown how to proceed. The third and the fourth pairs contained temptations for typical errors: namely for matching according to contextual and categorical associations, as opposed to the required material associations. (By contextual association we mean the combination of two objects that might easily appear together in a natural context, i.e., cigarette lighter and cup of coffee, as in “he put the lighter down beside his cup.” Categorical association on the other hand combines two objects on the basis of their belonging to a common class of objects. While contextual association could be based on the objects themselves, categorical association has to be based on a general concept like “porcelain figure” ; there is no particular object corresponding to figure.) As expected, all patients who did commit errors in these two pairs made one or both of the intended mistakes (12 out of 16 patients). The 14 patients who had started with the two correct pairs could solve the remaining two either correctly or by false contextual and categorical associations. This gave us the opportunity to demonstrate possible errors in other pairs and make the patients aware that not simply any matching would do, but only arranging according to one particular characteristicnamely the material. As a rule patients were-with a little help-able to correct their mistakes. All patients showed a marked reaction of sudden enlightenment when they saw the right solution. Then, and only then, was the actual test performed. At the beginning of each series the patients were reminded of the task. With two exceptions all patients showed over and again that they found the task difficult and were not satisfied with their performance. For a number of reasons the original group was reduced to 12 patients who were given the TT in a shortened version a week later (Spreen & Benton, 1969, plus the last item of the original version, i.e., 40 items and 170 points). Results are shown in Table 1. With the exception of one case of conduction aphasia the rank-ordered TT and matching task error scores were very similar. TT scores gave a reliable picture of overall severity of aphasia when checked on results of the detailed language exams done by the clinic’s

ANNETTE

AGE,

SYNDROME,

ERROR

K. BIRCHMEIER

TABLE 1 SCORESIN TOKEN TEST AND MATCHING

TASKS

Error scores matching task Verbal cuing

Age P.L. A.R. F.P. S.G. A.S. L.D.

30 72 56

P.S.

55

G.L. J.L. A.L. J.S. H.H.

45 65 63 19 73

75

62 75

Syndrome Global Jargon Jargon Wemicke Wemicke Wemicke Broca Mixed Broca Amnestic Amnestic Conduction

Average error score

TT

Nonverbal

36/113 331105 351104

14 12 13

271 65

11 11

18/ 55 241 221 16! 121 IO/ 61 41

9 a a

Total 5 7 4 3 3 4 2 2

41 39 23 19 13 6 5

10 2 2 9

-

201 49

9

Perseveration 5 3 2 -

1 1 1 1

1

-

3

3

2.8

1.4

Other

4 2 3 2 3

-

1 1 1

1.4

staff. The question arose whether the TT raw scores ought to be corrected as to age (Orgass, 1976) or level of education (De Renzi & Faglioni, 1978). The data indicate that the matching task was sensitive to overall aphasic impairment, but there is no means of correcting the scores of that task. One-sided correction of TT scores might only distort correlation. With one exception (a pianist) the level of education was quite similar (no college or university education). Moreover, the aged patients were a select group, chosen by a first-class psychological team because of good prognosis for reeducation. In view of these facts it seemed reasonable to base correlations on TT raw scores. Correlation between the rank orders of the two tasks was highly significant (Spearman rank correlation; p < .Ol) whether based on TT item scores or point scores. It was felt that the case of conduction aphasia may have regained most faculties needed for TT performance and that the matching task tested some particular difficulty, especially as the speech therapist watching the testing was quite aghast to see his patient unexpectedly fail on so easy a task and thought for a moment that we may have picked a bad day, but we had not. We therefore looked at correlation between the two tasks in the group without the case of conduction aphasia. The level of signiticance was raised top < .OOl. To make sure that the matching task did not differ fundamentally from similar tasks (Basso et al., 1976; Kelter et al., 1976), five aged patients with right hemiplegia without aphasia were given the test. One made four mistakes (he was a 71-year-old unskilled laborer with very little schooling), one, two, and the other three, none. In the matching task the 16

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TEST

103

aphasics made 144 mistakes while there were but two mistakes in a matched control group of 16 normal subjects (a craftsman did not distinguish between bronze and iron and thus differed from all the other normal subjects in two pairs). As 15 out of 16 patients had succeeded in assorting no less than three pairs correctly at least once in three series their performance significantly differed from chance performance (p < .OOOOOOOl). This and the results in the series which had been used for exercise made clear what seemed a rather strange fact: The patients had understood the task. They were aware of material properties, yet something kept them from following the matching principle throughout. The high correlation with TT scores proves that difficulties depended on severity of aphasic impairment. As already indicated by the preliminary exercise, wrong answers were not due to chance performance. Figure 1 represents the response matrix of the first series. There is marked clustering of alternative answers beside significant clustering of correct answers. Aphasics constantly matched the given pictures to several associative categories: material, semantic-logical affinity (wooden chest/ settee), and contextual affinity (street with rails/shoe). Distribution of correct, alternative, and chance answers is shown in Table 2. The results were surprising since the series had not been designed to test preferred associative categories although a few alternative answers had been built in to avoid frustrating patients with severe aphasia. One

imn

leather

rails

settee

FIG. 1. Matrix of matching task: aphasic matching according to material series I. Each patient is assigned one small square according to his total error score (highest error score: top left hand comer). H, Right answer; 0, wrong answer; x , alternative answer. Levels of significance: * p < .OS; ** p < .Ol.

ANNETTE

K. BIRCHMEIER

TABLE 2 NUMBER AND TYPES OF ASSOCIATIVE RESPONSES Alternative answers Correct

Erroneous

Total

Categorical

Contextual

Odd

Series I Series II Series III

50 56 38

46 40 58

43 32 51

20 18 29

23 14 22

3 8 7

Total

144

144

126

67

59

18

hundred twenty-six wrong answers can be assigned to clear alternative associative categories and only 18 cannot be clearly classified and are listed as odd responses. There was significant clustering in alternative answers to 5 out of 18 items (Table 3), four such clusters coincided with the built-in alternative answers. These alternatives seem to have acted as distracters. Actually the third series where two such alternative answers had been built in (straw hat/fur cap; tire/iron wheel) proved the most difficult for the aphasics. The question arose whether there might be some similarity between aphasic matching in the task and normal matching in free association. To test this, a group of 16 normal subjects (aged 16-65 years, average 40.2 years) were asked to match the pictures into meaningful pairs. Figure 2 shows the matrix for performance in series 1. Clustering is also very obvious in free matching of normal subjects. They matched nearly as frequently according to material, as aphasics did in the bound condition. Table 3 compares aphasic bound matching and normal free matching. Normal matching in free condition showed a marked tendency to follow material characteristics. In addition there was significant clustering for nonmaterial matching in 10 items out of 18. The five pairs that had reached a significant level for clustering of alternative answers in aphasic matching TABLE 3 COMPARISON OF APHASIC MATCHING ACCORDING TO MATERIAL AND NORMAL MATCHING IN THREE SERIES OF MATCHING TASKS( 18 PAIRS) Aphasic bound Matched according to material Total Alternative matching Total

I II III I II III

FREE

Normal free

50 56 38

48 39 53

144

140

46 40 58

48 41 43

144

148

TOKEN

TEST

identical

wooden

iron

carthe"

8:

6

different

7:

8

identical

0:,3

board

rails

UP" 7:

golden

leather

watch

settee

different

9:11

identical

7:

6

5

FIG. 2. Matrix of matching task: normal subjects free association series I. Each subject is assigned one small square according to his total number of alternative answers (highest altern$ive score: top left hand comer). n , Material choice; 0, nonmaterial choice; x, alternative answer. Levels of significance for main clustering in nonmaterial matching: * p < .05; **p < .Ol; ***p < .ool.

were significant in normal free matching as well. Main clustering (whether sign&ant or not) of alternative answers in the 18 pairs of the task was identical in nine, similar in three, and different in six items between groups. Thus aphasic behavior in bound matching and normal behavior in free matching are similar in some points but differ in others. It seems that associative strength plays an important role for aphasics in the solution of the task. This corresponds with results found in a study of word retrieval by Wiig and Globus (1971). It has been argued that aphasics did not retain well-defined concepts, and that they relapsed to the level of children in conceptual thinking. The results of our matching tasks hardly support the second view. To test the first one further the same three series were used for another experiment. The response pictures were arranged in a line on the table and the stimulus pictures shown one after the other. The same random order was used as before. For each picture shown the material was named (but not the object) and the patients had to point to the second picture with an object made of the same material. This was done immediately after nonverbal matching of the three series. Our hypothesis was that if patients had not retained well-defined concepts they would still find it difficult to match pictures according to given material characteristics, for all we could offer them was the sound of the word denoting a concept, the concept itself necessarily had to be fur-

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ANNETTE

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nished by the patient’s mind. Ability to judge whether a given material is present in a given object or not presupposes the concept of material quality and the ability to analyze pictorial data efficiently so as to arrive at significant features. Detailed results for the 12 patients with TT scores are to be found in Table 1. Error scores dropped dramatically (Table 4) but there are still a number of errors and a high correlation with TT scores is preserved (p < .Ol). This seems to substantiate the theory of a “conceptual disorder concomitant with aphasia” (Goldstein, 1924; Kelter et al., 1976). More than half of the errors were due to perseveration now but perseveration played only a minor role in Wernicke cases. Mistakes that were due to obvious semantic confusion (e.g., iron-silver) were listed separately. These results do not support the hypothesis of a uniform, general conceptual disorder in aphasia but they definitely confirm the findings of Cohen, Kelter, Engel, List, & Strohner (1976) that “it was no longer defensible to consider the TT exclusively as a test of auditory verbal comprehension.” DISCUSSION The experimental results for aphasics and for normal subjects in the matching tasks and the high correlation with TT scores raise a number of questions. The present results permit nothing more than suggestions and tentative answers. Performance of matching without verbal cue certainly depended on the following capacities: (a) unimpaired visual analysis of pictorial data, (b) the capacity of producing associations, (c) sampling associations according to a given principle, (d) ability to move from one idea to the other while sampling. Thus errors may be due to lack of production, lack of comprehension, lack of precision in analyzing visual data, a deficit in conceptual thinking, and to perseveration as well as to unknown factors. All factors may contribute to error scores in different degrees for different syndromes. The present results support the already well-substantiated hypothesis that associative matching is fundamentally disturbed in nonverbal tasks when it demands extended matching. In addition, the present investiga-

TABLE NUMBER

AND TYPES OF APHASIC

4

REWONSES

IN Two

MATCHING

TASKS

Number and types of aphasic responses

Nonverbal Verbal cue

Correct

Erroneous

Alternative

Other

144 242

144 46

126

18 11

Semantic 10

Perseveration 25

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tion shows that verbal tags will greatly facilitate the task. How are such seemingly purely perceptive and conceptual tasks related to the Token Test? The correlation between TT and matching scores was astounding in our group. The Token Test is, after all, clearly a test of auditory verbal comprehension-whatever else it might be. It is very simple on the perceptual level and makes use of simple objects with obvious characteristics: circles and squares, big and small ones in five clear colors. One may therefore speculate that aphasics do not clearly perceive the material quality of objects when this quality has to be inferred, but to suppose that an aphasic does not see a circle when there is one means he would not see the full moon shining clearly in the sky. Moreover, proof of difficulties of a linguistic nature has been substantiated by the studies of Poeck et al. (1974) and Lesser (1974). We also know that short-term verbal memory is involved in TT performance. Efron (1963) observed that a defect in sequence discrimination was found only when some degree of aphasia was present. A defective capacity for temporal sequencing of auditory stimuli in aphasics in contrast to nonaphasic brain-damaged patients has been demonstrated since (Goodglass, Gleason, & Hyde, 1970; Albert, 1972). In a further study Albert (1976) showed that three types of errors occurred: substitution, omission, and sequencing errors. All three may greatly impair Token Test scores. The same study by Albert shows that only for aphasics the influence of defective memory of sequences becomes more pronounced as the information load increases. The nature of substitution errors was not specified and no items were given, so the data do not permit any judgment of whether semantic confusion occurred or not. In a small study on naming and auditory recognition errors in 10 young, well-educated, normal subjects (Birchmeier, 1976) it was found that semantic confusion occurred with very short reaction times (t < 1 set). In the TT a purely serial disturbance will produce an answer where a square and a circle, a red and a green token are touched in response to the command: “Touch the red circle and the green square.” All semantic elements will be preserved. Semantic confusion on the other hand will produce an answer where two circles or two squares or (and) tokens of any color are touched. All these factors do not come into matching task performance. The high correlation between the two tests is therefore very puzzling. Perhaps the insistence on the evident contrast between verbal and nonverbal mode of presentation ought to be discarded. We then find that both tests are based on very general properties of objects. Objects always have particular color characteristics while “material” is just as general a property as color is. From the point of view of feature analysis color and material are but two among many features and they both can but must not be distinctive for a given object name. In the TT the number of distinctive features is very small in different tokens: small/big, round/square, and five colors.

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In addition, these nine features belong to three semantic clusters only: one concerning size, one color, and one encompassing symmetrical geometrical figures. If but one feature is only vaguely remembered in executing a TT order or if its semantic implications are only vaguely understood, confusion is sure to follow. In the matching task the property “material” is embedded in a great variety of properties in different objects. Most features of these objects have to be disregarded and analysis has to go on till the one feature vital for the task is singled out. But in both tasks a concept has to be built from isolated features. “Red” and “circle” have to be merged into the distinct concept of “red circle” in the TT while “iron rail” and “iron keys” have to be merged into the concept of “iron objects.” Nothing else would do. Thus there is again a great similarity and a great difference between the two tasks. Another strange contrast becomes evident when language is seemingly taken out of the TT and when it is introduced into the matching task. For when the TT was presented in a visual form (Cohen et al., 1976; Brookshire, 1978) aphasic performance significantly improved, while performance significantly improved in our matching task when verbal cuing was added. Yet whether language was taken out of the TT or introduced into the matching task aphasic performance still significantly differed from normal performance in both tests. When we look at nonperseverative mistakes only in the verbal cue condition of the matching test, we find that our case of global aphasia performed as well as the three cases with the best TT scores. Much more experimenting is needed to unravel the thread leading us through this truly labyrinthine problem. CONCLUSIONS

It may be useful-for practical reasons-to define as verbal only alphanumeric tasks. All other tasks are classified as nonverbal. However this may be a heuristic definition and language strategies may still be covertly present and even decisive in solving tasks with nonverbal stimuli. On the other hand nonverbal factors may come into seemingly verbal tasks like the TT. The combination of associative and alphanumeric tasks has proved quite efficient in therapeutic practice (Birchmeier, 1979). Feature analysis links the TT to the matching tasks in this study. But feature analysis is only elaborate in auditory analysis and in the final section of the TT on the syntactical level. For the TT, auditory verbal short-term memory is of great importance especially for the two final parts. In the matching task feature analysis is important in the visual modality. Short-term memory comes in on a very simple level, as there is no time limitation. Essential are the ability to call up associations, the ability to analyze them competently, and to be able to move from one association to another. The TT is predominantly receptive. There are expressive elements, however, as a concept has to be built up from

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isolated features as well as a motor performance scheme. Matching tasks have a strong expressive element. Inner sampling of associations is essentially expressive and so is building a new associative unit from two pictures chosen among a number of others. In this, matching resembles building a sentence out of words. In both tasks a concept has to be built from isolated features and in both tasks a lack of inner verbal mediation and perseveration are severe handicaps. They may link up with a tendency for substitution in the TT and will pin the aphasic down to the most obvious but erroneous answer in the matching task. Thus a number of factors, some common to both, some typical for one task only, may bring about the effect of sensitivity to language disturbance and grading according to severity of impairment. When viewed in a detached mood aphasic and normal performance in our matching task may teach us an astonishing lesson. In our common philosophy we tend to consider material substance as an elementary property of objects, the true essence of reality. But given a little associative disturbance or a slight change in experimental instructions the apparent solidity of the characteristics of different materials fades into the background. The inherent substantial and logical principles of our task were over and again disregarded. Form (gestalt), function, and context and not the quality of materials catch the eye, which reminds us that reality is but in ourselves-‘ ‘ all the mighty world of eye and ear,-both what they half create and half perceive” (Wordsworth). REFERENCES Albert, M. L. 1972. Certain aspects des troubles de la comprehension auditive du language. Langages, 7, 37-51. Albert, M. L. 1976. Short-term memory and aphasia. Brain and Language, 3, 29-33. Basso, A., Faglioni, P., & Spinnler, H. 1976. Non-verbal colour impairment of aphasics. Neuropsychologia, 14, 183-193. Birchmeier, A. K. 1976. Pidagogische Aspekte der Aphasie und der Aphasietherapie. Nervenarzt,

41, 24-28.

Birchmeier, A. K. 1979. Die Aphasie als menschliches und therapeutisches Problem: Zur Rehabilitation von geriatrischen Patienten. In G. Peuser (Ed.), Studien zar Sprachtherapie. Miinchen: Fink, 1979. Boller, F., & Vignolo, L. A. 1966. Latent sensory aphasia in hemisphere-damaged patients. An experimental study with the Token Test. Brain, 89, 815-830. Brookshire, R. H. 1978. A Token Test battery for testing auditory comprehension in brain-injured adults. Brain and Language, 6, 149-157. Cohen, R., Kelter, S., Engel, D., List, G., & Strohner, H. 1Y76. Zur Validitat des Token Tests. Nervenarzt, 47, 357-361. Cohen, R., Kelter, S., & Schafer, B. 1977. Zum Einfluss des Sprachverstlndnisses auf die Leistungen im Token Test. Zeitschrifrflr klinische Psychologie, 6, 1-14. De Renzi, E., & Vignolo, L. A. 1962. The Token Test, a sensitive test to detect receptive disturbances in aphasics. Brain, 86, 403-424. De Renzi, E., & Faglioni, P. 1978. Normative data and screening power of a shortened version of the Token Test. Cortex, 14, 41-49.

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