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Linguistic and nonlinguistic processing of narratives in aphasia
BRAIN
AND
LANGUAGE
16, l-18
(1982)
Linguistic and Nonlinguistic Processing of Narratives in Aphasia WALTER
HUBER
AND JOCHEN GLEBER
Rheinisch-Westftilische Technische Hochschule Aachen A scrambled Story Test was given to four subgroups of aphasic patients and to one group each of right-hemisphere-damaged patients and of normal controls. Subjects were asked to construct narratives from an unordered set of pictures and from unordered sets of corresponding sentences. Two verbal versions were distinguished, one with high and one with low linguistic cohesion among sentences. As expected, we found interactions between aphasic and nonaphasic behavior, such that aphasic patients made relatively more errors on the verbal versions and right-hemisphere patients on the pictorial version. High versus low linguistic cohesion, however, had no differential impact. It is concluded that brain-damaged patients when processing texts generally rely on macro- rather than on microstructure information. Furthermore, two control tests were administered: the Token Test and a sentence-to-picture matching task with either descriptive or nondescriptive stimulus sentences. Various patterns of correlation between these control tests and the Scrambled Story Test were found. The findings are interpreted in terms of a differential involvement of descriptive versus pragmatic processing strategies.
INTRODUCTION In general linguistics, a discourse or text is viewed not just as an enumeration of sentences, but is defined and described by properties of its own on the stylistic and/or syntactic level as well as on the semantic level. The most prominent semantic characteristics of texts is the overlap between the propositional structures of its sentences. The degree of propositional overlap determines the coherence of a text (van Dijk & Kintsch, 1978). There are many lexical and syntactic devices that make evident the coherence of the situations described by a text. Among these devices are coreference relations, attributive and adverbial specifications, The authors wish to thank Klaus Willmes for the statistical evaluation of the data and Klaus Poeck, Dorothea Weniger, and Ria de Bleser for their many helpful suggestions on carrying through this study and on preparing this paper. Reprint requests should be addressed to Dr. Walter Huber, Abt. Neurologie, RWTH Aachen, Goethestr. 27-29, 5100 Aachen, Federal Republic of Germany.
0093-934X/82/030001-18$02.00/0 Copyright 0 1982 by Academic Press, Inc. All rights of reproduction in any form reserved.
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changes in word order, paraphrases, repetitions, and the like. These devices all contribute to the linguistic cohesion of a particular text (Dressler, 1973). Some of the experimental work in psycholinguistics gives evidence to the point that the processing of texts depends more on semantic than on stylistic or syntactic factors. For example, Kintsch (1974) demonstrated that high versus low syntactic complexity of texts has no impact on the accuracy of recall. On the other hand, Haberlandt and Bingham (1978) showed in a reading task study that the degree of semantic and logical coherence influences the processing of texts. It must be stressed, however, that semantic coherence of a text cannot be strictly kept apart from the stylistic and syntactic cohesion of a text. Haviland and Clark (1974) argue that new information in a text can be more easily understood if the new information is linguistically tied to “given” information, i.e., information mentioned before by means of linguistic cohesion devices. Furthermore, the coherence of a text does not depend on its propositional structure alone. Pragmatic factors are also involved. The hearer incorporates information provided by the situation in which a text occurs and to which it refers. This information will be mediated by the hearer’s experiences, expectations, and so on. Thus, the hearer is involved in both verbal and situational contextualization when he is confronted with a text (Fillmore, 1974). By contextualization we mean general cognitive processes, such as inference, deduction, and problem solving, that supplement the hearer’s lexical and grammatical knowledge and are the means by which he will eventually reconstruct the series of events described in a particular text. Contextualization is, of course, not restricted to linguistic material. For example, when we look at cartoon stories we also make contextualizations. But instead of observing lexical and syntactic cohesion devices we might pick out various pictorial cues which make it easier to comprehend the series of events depicted. So far, only a few studies have dealt with contextualization in conditions of brain damage. In a text-to-picture matching task, Stachowiak, Huber, Poeck, and Kerschensteiner (1977) found that aphasic patients made only insignificantly more errors than right-hemisphere-damaged and normal controls. In a picture arrangement task, Veroff (1978) studied two features of pictorial contextualization. Subjects had to recognize changes of category in the development of an organism (e.g., a tadpole growing into a frog) and they had to recognize changes of place in the movement of an object (e.g., a golf ball rolling toward the hole). Veroff’s results indicate the possibility of a differential hemispheric involvement. Her three patients with large left-hemisphere lesions had more difficulties with change of category sequences than her six right-hemisphere-damaged patients, who made more errors on the change of place sequences. A specific involvement of the right hemisphere in visual-spatial tasks
PROCESSING
OF NARRATIVES
3
was demonstrated in many clinical studies (for review, cf. Milner, 1974; Sperry, 1974). Processing of more complex visual information, however, seems to be affected by lesions in both hemispheres, especially in the retrorolandic areas (Orgass, Hartje, Kerschensteiner, & Poeck, 1972; Basso, DeRenzi, Faglioni, Scotti, & Spinnler, 1973). With respect to the performances in the picture arrangement task of the Hamburg Wechseler Intelligence Scales, Orgass et al . (1972) did not find significant differences between aphasic patients and right-hemisphere controls. This finding might reflect either a general intellectual deficit in verbal mediation or in visual-spatial processing in either one of the two groups. It is an unresolved question whether there are common cognitive strategies underlying contextualization in both the pictorial and the linguistic mode of presentation of a narrative. In general, it is questionable whether there is a common cognitive basis to language and thought and what this basis might be. With respect to aphasia two alternative positions have been taken. On the one hand it has been claimed that the linguistic disturbance is a consequence of an underlying cognitive impairment. Such a position was taken most explicitly in the work of Bay (e.g., 1962). According to Bay (1960), the poor performance of aphasic patients in rendering verbally what they had seen in a cartoon story is caused either because of their inability to contextualize the pictorial information or because they cannot comprehend specifically the humor which is expressed by these stories. On the other hand, opponents of this view hold that aphasia is primarily characterized by specific disturbances of elementary lexical and syntactic abilities. An impairment of nonlinguistic cognitive abilities does not necessarily coincide with the occurrence of aphasia (cf. Zangwill, 1978; Lebrun & Hoops, 1974). From this view point, the poor performance of aphasic patients that was reported by Bay would be due to linguistic difficulties in their expressive verbal behavior. Hatfield and Zangwill (1974) reported of a patient with severe and persistent aphasia who was substantially unimpaired when he was asked to communicate a sequence of events by drawing in spite of severe defects in his spoken and written expression. From data like these it seems that aphasia cannot be reduced to a general intellectual impairment. However, more conclusive evidence is lacking. When investigating these questions, one has to make sure that the same or at least similar cognitive problems have to be solved in a nonlinguistic and in a linguistic mode of presentation. It was within this context of questions that we had aphasic and nonaphasic brain-damaged patients as well as normal controls construct narratives from an unordered set of pictures and from an unordered set of corresponding sentences. If, in such tasks, aphasic patients fail in both modes of presentation and if they are inferior to the nonaphasic controls even in the
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nonlinguistic mode, then the view that aphasia is an outcome of a specific intellectual deficit rather than a specific linguistic one, could not be refuted. But if one believes that aphasia is mainly a specific linguistic deficit then one should, of course, expect that clear differences between aphasics and controls will be found in the linguistic mode of presentation, but no differences in the nonlinguistic mode. If one, furthermore, doubts that the apparent common basis of language and thought will be specifically affected in conditions of brain damage, then one should expect both right-hemisphere and aphasic patients to show a clear difference between verbal and nonverbal processing, but in reverse directions, such that in right-hemisphere patniets’ nonverbal processing is more affected than verbal processing. In addition, we wanted to find out whether the linguistic processing of texts in such an arrangement task depends more on macro- than on microstructure information. The difference was controlled by two versions of the sentence arrangement task, one with low and one with high linguistic cohesion. If subjects predominantly rely on the core sequence of events, i.e., on the macropropositions of the text, then their level of performance should be substantially unchanged when they are provided with versions of higher cohesion, i.e., with additional microstructure information. This expectation follows from a previous investigation of text comprehension in aphasia (Stachowiak et al., 1977), as well as from a study of normal subjects who were asked to read and recall written texts (Vipond, 1980). MATERIALS AND METHODS Subjects Four groups of aphasic patients, a group of right-brain-damaged, and a group of normal controls were studied. Each group included 18 subjects. The aphasic groups were samples of the four major clinical syndromes of aphasia: global, Wemicke’s, Broca’s, and amnesic aphasia. Classification of the syndrome was based on standardized clinical examination (Kerschensteiner, Poeck, Huber, & Stachowiak, 1975; Poeck, Kerschensteiner, Stachowiak, 8~ Huber, 1975). The following features of spontaneous speech were taken as main characteristics: nonfluent, highly automatized speech for global aphasia; fluent, paragrammatic speech, semantic, and/or phonemic paraphasias for Wemicke’s aphasia; nonfluent agrammatic speech and phonemic paraphasias for Broca’s aphasia; word-finding difficulties for amnesic aphasia. In most aphasic and in all brain-damaged control patients, the lesion site was assessed by evaluation of CT scans or EEG recordings. The normal controls were also patients from the neurological wards having no signs of an involvement of the central nervous system. The distribution of age, sex, etiology, duration, and site of lesion is summarized in Table 1. The aphasic subjects were either in- or out-patients in the course of speech therapy. Therefore age and duration varied considerably among the aphasic subgroups. Similar differences were reported in other clinical studies (e.g., Kertesz & McCabe 1977). Educational and occupational level, however, was quite comparable among the groups. All subjects had finished elementary school and no more than two subjects of each group had full academic training.
8 5 5 7 11 6
Female
10 13 13 11 7 12
Male
a p: prerolandic, r: retrorolandic. b RH: right hemisphere; N: normal.
Global Wemicke Broca Amnesic RI-I control2 N controls*
Group (n = 18)
Sex
48.6 58.4 43.0 47.3 48.2 42.3
Mean age tye=s) 15 16 15 15 13 -
Vast
-
3 2 3 3 5
Others
Etiology
31.1 10.6 18.8 3.9 13.1 -
Mean duration (months)
TABLE 1 SAMPLECHARACTERISTICS
1 1 11 6 7 -
P
0 11 0 7 5 -
r
17 1 3 2 6 -
p+r
Site of lesion”
-
0 5 4 3 0
Unknown
% “c E
5
%
8 z 5 Q
g
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HUBER AND GLEBER
Material Scrambled Story Test. The test consisted of one pictorial and two verbal versions. In all three versions, the unordered elements of a story-pictures or sentences-had to be rearranged into the correct order. The task was demonstrated by one example for the pictorial and one example for the verbal versions. The subjects were told that they had to consider all presented pictures or sentences for a correct solution, there was no time limit imposed and the patients were asked to indicate when they had finished. Patients who did not comprehend the task on demonstration were excluded. This was the case with five additionally seen patients, four patients with global and one with Wernicke’s aphasia. A total of nine little known cartoon stories of six pictures each were selected from Plauen (1949, 1951, 1952) and from Kossatz (1972). They were similar in style and depicted scenes from everyday life featuring a man and his little son or his dog. An example of the cartoon stories is given in Fig. 1. Two written versions of each story were constructed, one with high and one with low linguistic cohesion as illustrated in Table 2. In both verbal versions, each of the six sentences corresponded to one picture of the original cartoon story. In the low-cohesion version, the syntactic structure of the sentences was as simple as possible and only familiar content words were used. No attributive or adverbial specifications of the events described were given. Thus we obtained rather nonredundant texts. The only cohesion devices we used were repetition of content words and variation in the indefinite and definite articles, marking new versus old information. In the high-cohesion version, the sentences were characterized by complex syntactic structures and many attributive and adverbial specifications. The single sentences were interconnected by stylistic and semantic devices, such as topicalization of constituents and embedding of temporal or causal clauses. The two verbal versions differed in length. In the low-cohesion version the mean number of words per sentence was 6.8 with a range from 3 to 11, and in the high-cohesion version 15.5 with a range from 9 to 21. In both verbal versions the core
FIG. 1. Example of the pictorial version of the Scrambled Story Test (cartoon story taken from Kossatz, 1972).
PROCESSING OF NARRATIVES
7
TABLE 2 EXAMPLES OF THE Two VERBAL VERSIONSOF THE SCRAMBLEDSTORY TEST(TRANSLATED FROM THE ORIGINAL GERMAN)
1. Low linguistic cohesion (1) A man is hit on the head by a flower pot (2) The man scolds the woman on the balcony (3) The man and his dog enter the house (4) The man knocks on the apartment door (5) The woman gives the dog a bone (6) The man kisses the woman’s hand 2. High linguistic cohesion (1) While walking down the street with his dog, an elderly gentleman was suddenly hit on the head by a flower pot falling from a balcony (2) Both master and dog scolded the culprit on the balcony angrily at the top of their voices (3) In order to teach him a lesson, they entered the house purposefully (4) They stopped on the second floor and the gentleman knocked on the apartment door with his cane (5) An elderly lady opened the door and, full of sympathy, comforted the dog with a bone (6) This made the elderly gentleman feel good and he gallantly kissed the lady’s hand
sequence of events was exactly the same and was based on the original cartoon story. In other words, in all three versions of each narrative we tried to keep the logical and pragmatic coherence features (the “macrostructure”) as constant as possible, but varied systematically the propositional “microstructure” of the two written versions of the narrative. This difference in microstructure is reflected by high versus low linguistic cohesion. The size of stimulus pictures was 11 x 8 cm. The unordered set of pictures was given in a single row as in the picture arrangement task of the Wechsler Intelligence Scale. The stimulus sentences were printed in capital letters on index cards with a size of 21 x 4 cm. The unordered set of sentence cards was represented and had to be rearranged in a vertical array. Visible only to the investigator, the stimulus order was specified by the alphabetic letters A, B, C, D, E, F, that were printed on the back of the stimulus cards. In all items, the number of elements that had to be reordered for a correct solution was 3 or 4. With incorrect reactions, the degree of deviation was estimated by means of an error score: proceeding in the direction of the correct order, we counted the minimal number of permutations of single elements or of chains of elements that were necessary to yield the correct solution. The correct order was also marked on the back of the stimulus cards by numbers from 1 to 6. False sequences like l-3-4-2-5-6, l-2-4-3-5-6, 2-l-3-4-5-6, 3-4-l-2-5-6, 4-5-6-l-2-3, etc. would score as 1, 2-l-4-5-3-6 as 2, 2-l- 5-4-3-6 as 3, and so on. The maximum possible score of 5 would result if the correct sequence were completely reversed to 6-5-4-3-2-l. This reaction occurred only once, namely, in the pictorial version of the task, and was counted as correct, as the patient indicated that the sequence should be read from right to left. As an alternative to this kind of scoring, permutations of chains of elements could be counted as multiple permutations of single elements. But this seemed psychologically less plausible. For example, a false sequence like 4-5-6-l-2-3 scores as 1 in our system, but would score as 3 in the alternative system. Sentence Comprehension Test. Subjects were asked to silently read a sentence. fmmediately afterward a multiple-choice set of four pictures was presented. The subject had to point to the one picture that corresponded best to the meaning of the sentence. We distinguished two sets of stimulus sentences. In the one set, nondescriptive sentences like
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HUBER AND GLEBER
“He is going to be put in jail” were given. The set of multiple choice pictures used for this particular sentence is illustrated in Fig. 2. The appropriate reference situation is depicted on the bottom left. Confusion would occur if the subject just took the lexical meaning of a single key word like “jail” in the given example. Then, subjects would most likely point to the distractor picture, the one on the top right of Fig. 2. The distractor picture represented a situation which pragmatically precedes or follows the reference situation of the target sentence. Using the same set of pictures but in different order, a second set of sentences was constructed. These were fully descriptive sentences like “The policeman who caught a criminal is now forcing him to hold back his arms and is searching him for weapons.” In this type of sentences the target situation is fully specified and described in redundant form. There were 10 items for each set of sentences. The total of 20 items was split into two blocks, such that the two sentence types were equally distributed and only one of the two sets of multiple choice pictures occurred within one block. The order of sentence types was varied across the 10 items of each block. It was hypothesized that the nondescriptive sentences would require more situational contextualization than the descriptive ones and that they therefore should be more closely related to the text with low rather than high linguistic cohesion. Token Test. In order to control the possible influence of reading performance, part III of the Token Test in the revised German version (Orgass, 1976) was given in two modes of presentation: one auditory and one visual. As in the text-sorting task, there was no time limit on reading, and the written instructions remained uncovered until the subject had finished pointing to the tokens.
t
d
FIG. 2. Example of the multiple-choice pictures used in the Sentence Comprehension Test.
9
PROCESSING OF NARRATIVES
Procedure The 27 items of the Scrambled Story Test were divided into three blocks. Within each block, each of the nine stories occurred either in the pictorial version or in one of the two written versions. Thus, each mode of presentation occurred three times within each block, but each story only once. In order to control possible position effects, the six possible combinations in ordering the three blocks were varied from patient to patient. Each order of blocks was given to three of the 18 subjects in each group. This procedure made it possible to detect differences in performance depending on whether the pictorial version came first, second, or last with respect to the two verbal versions of the same story. The blocks of the Scrambled Story Test and of the two control tests were given in the following order: Auditory Token Test (10 items), Story Test (9 items), Sentence Test (10 items), Story Test (9 items), Sentence Test (10 items), Story Test (9 items), Visual Token Test (10 items). In contrast to the Story Test, the order of blocks of the two control tests remained the same for all subjects.
RESULTS Scrambled
Story Test
The mean error scores and the standard deviations in the nine items of each of the three versions of the test are given in Table 3. The error scores of one item count the number of segments out of six that were placed into a wrong position. The number of misplaced segments given in the stimulus sequence of one item was either 3 or 4, and 31 in all 9 items. Error scores substantially lower than this were found for all groups in the pictorial version, which indicates that their performances went in the direction of the correct solution. The most difficulties occurred with the two verbal versions in the two most impaired aphasic groups, viz., patients with global and Wemicke’s aphasia. They performed nearly at chance level. As expected, there are numerical interactions between the pictorial TABLE 3 MEANS
AND STANDARD DEVIATIONS OF ERROR SCORES IN THE THREE VERSIONS OF THE SCRAMBLED STORY TEST (NINE ITEMS EACH)
Pictorial version
Verbal versions Low cohesion
n = 18 Global Wemicke Broca Amnesic RH controls N controls
High cohesion
Mean
SD
Mean
SD
Mean
SD
13.1 15.6 8.6 7.6 11.8 5.1
(6.2)
20.7 19.6” 11.6 7.7 7.2 3.3
(3.9) (7.2)
20.3 19.6” 11.0 6.0 7.0 1.6
(4.8) (7.9) (8.4) (3.9)
(7.3)
(6.2) (4.1) (7.8) (3.2)
(8.2) (4.1)
(6.6) (2.5)
(6.8) (1.8)
’ No substantial reduction of permutations when compared to the total number of permutations given in all nine stimulus sequences (N = 31); binomial tables, a = 1%.
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HUBER
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and the two verbal modes of presentation. The nonaphasic controls had more difficulties with the arrangement of pictures than with sentences. The reverse tendency holds true for the patients with global, Wernicke’s, and Broca’s aphasia. Differences between the two verbal versions seem to exist only in amnesic aphasics and normal controls. In both groups, the high-cohesion texts caused the least difficulties. The data were analyzed by univariate analysis of variance using a split-plot design. Because of heterogeneous variance-covariance matrices (x2 = 80, 7 > x2 (30, 90%) = 40, 3) we made a correction for the degrees of freedom (Kirk, 1968). We found a significant interaction between the group factor and the task factor (F = 11.94 > F(10 corrected to 5, 204, 95%) = 2.26). Significant simple main effects were found for the group factor in all three versions of the task and for the task factor with respect to global and Wernicke’s aphasics and to right-hemisphere controls. In Broca aphasics and normal controls the F values were close to being significant (Broca’s: F = 5.30, Normals: F = 5.26; F(2 corrected to 1, 204,99%) = 6.76; F (uncorrected) = 4.71). No influence was found for amnesic aphasics (F = 1.49). Succeeding pairwise comparisons using simultaneous test procedures (Gabriel, 1969) yielded the following result: (1) Pairwise comparisons between groups Pictorial version WE GL RH Verbial versions Low cohesion High cohesion
BR
AM
NC
GL
WE
BR
AM
RH
NC
GL
WE
BR
AM
RH
NC
(2) Pairwise comparisons between modes of presentation PICT LOW Global aphasia Wernicke’s
PICT
LOW
HIGH HIGH
Broca’s
PICT
HIGH
LOW
Amnesic RH controls Normal controls
PICT PICT PICT
HIGH LOW LOW
LOW
HIGH HIGH Significant differences were found only between those groups/modes which are not connected by an underline. Between groups, the differences found in the verbal versions were more often significant than those found in the pictorial version. This is mainly due to the much larger number of difficulties that patients with global and Wernicke’s aphasia had with both verbal versions. When arranging sentences into narratives, all the aphasic subgroups-with the
PROCESSING
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11
exception of amnesic aphasics-had significantly more difficulties than normal controls, which is not surprising at all. In arranging pictures, significant differences were found between patients with Wernicke’s aphasia, who had the largest amount of difficulties, and all other groups except global aphasics and right-hemisphere controls. Furthermore, the performance of patients with global aphasia was significantly worse than that of the normal controls. Significant differences between the processing of the pictorial and of each of the two verbal modes were found for global aphasics and right-hemisphere controls. In none of the, groups, however, did we find significant differences between the processing of the two verbal versions of the test. This finding was quite unexpected. In order to control the possible effects of differences in order of presentation, the error scores of each patient were divided into three portions, depending on whether the pictorial version was presented first, second, or third. For each ordering, a separate analysis of variance was carried through, calling for a reduction of the alpha level from 5 to 1%. Again, we found significant interactions between the group factor and the task factor for each type of sequence. After assessing significant simple main effects, pairwise comparisons of differences between pictures and texts were carried through. We obtained the following differences (P = pictures; T = text with either low or high cohesion): Types of sequence
Groups Global Wernicke’s Broca’s Amnesic RH controls
P-T-T P-T-T P-T-T P-T-T P-T-T
T-P-T T-P-T T-P-T T-P-T T-P-T
T-T-P T-T-P T-T-P T-T-P T-T-P
Again an underline shows that no significant difference was found between the modes of presentation thus connected. The normal controls were not considered in this analysis because the variations in their error scores were too low. The global aphasics had significantly greater difficulties in arranging sentences than pictures in each type of sequence. For Wernicke’s and Broca’s aphasics, however, significant differences were found only when the pictorial version of the narrative was presented last. In contrast, the right-hemisphere patients had significantly greater difficulties with pictures than with texts only when the pictures were presented first. Thus, the general finding of an interaction between pictures and texts with respect to aphasic versus right-hemisphere patients depends partly on the order in which pictures and texts were presented. With respect to single segments, we found that neither type nor position significantly influenced performance. First, we ascertained that type and
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HUBER AND GLEBER
position of incorrectly arranged single segments were independent features (x2 test), second, that segments l-3 in contrast to segments 4-6 of the target sequence did not yield greater or smaller frequencies of errors; and third, that the errors occurred as frequently in the first three positions of the arranged sequence as in the last three positions (Wilcoxon-test, two-tailed). Thus, the errors were almost equally distributed across individual segments and positions. Furthermore, we tried to control the influence of lesion site in the right-hemisphere patient group on the processing of pictures versus sentences. The mean error scores in Table 4 indicate that patients with retrorolandic lesions had-as expected-the largest number of difficulties with the pictorial version of the task. Because of the small sample sizes, no statistical analysis was carried through. Control Tests In the sentence comprehension task the descriptive sentences were, as expected, less difficult than the nondescriptive ones. This can be seen from the mean numbers of incorrect reactions given in Table 5. Normal controls made no errors in either version of the task. Applying analysis of variance, we found significant differences between the processing of the two types of sentences for each of the groups. As in the Scrambled Story Test, we did not find reliable differences between the right-hemisphere controls and the two less impaired aphasic groups, namely the patients with Broca’s and amnesic aphasia. Only with nondescriptive sentences was the distractor picture chosen-as expected-more often than by chance. This was true for all aphasic groups (binominal test, (Y = 1%). The mean errors of the two versions of part III of the Token Test are given in Table 5 as well. The visual version was easier to solve in all aphasic groups, although we found no significant differences when apTABLE 4 DISTRIBUTION OF ERROR SCORES IN THE SCRAMBLED STORY TEST (NINE ITEMS) AMONG RIGHT-HEMISPHERE CONTROLS WITH RESPECT TO SITE OF LESION
Verbal versions RH controls Prerolandic n=7 retrorolandic n=5 Pre + retrorolandic n=6
M Md M Md M Md
Pictorial version
Low cohesion
High cohesion
7.4 3.0 (l-23) 17.0 18.0 (6-24) 12.7 11.o (5-20)
4.4 3.0 (O-14) 7.4 6.0 (3-13) 10.3 6.5 (l-24)
4.3 3.0 (O-16) 7.2 7.0 (3-12) 10.0 7.5 (O-23)
13
PROCESSING OF NARRATIVES TABLE 5 MEANS AND STANDARD DEVIATIONS OF INCORRECTREACTIONS IN THE CONTROLTESTS (10 ITEMS EACH)
Token Test
Sentence comprehension test Descriptive n = 18 Global Wemicke Broca Amnesic RH controls
Nondescriptive
Visual
Auditory
Mean
SD
Mean
SD
Mean
SD
Mean
SD
1.8 1.4 0.4 0.3 0.3
(2.1) (2.1) (1.0) (0.6) (0.5)
6.0 4.6 3.1 2.0 2.2
(2.4) (2.5) (2.1) (0.6) (0.5)
5.2 5.6 1.6 0.2 0.0
(3.7) (4.1) (2.7) (0.4) (-1
8.7 6.8 3.7 1.8 0.0
(1.8) (3.3) (3.5) (3.1) C-1
plying analysis of variance. Right-hemisphere and normal controls were not included because they did not make any errors in either version of the test. The relationship between the performance on both control tests and the Scrambled Story Test was assessedby correlation studies. The results are given in Table 6 and 7. With respect to the Token Test performance (cf. Table 7) high correlations were found only for the visual version. Rather surprisingly, the correlations for picture arranging were as high as those for sentence arranging. Comparing the performance in the Sentence Comprehension Test and in the Scrambled Story Test (cf. Table 6), we found the following patterns. In the pictorial version, the correlations for comprehending the descriptive sentences were numerically higher than for the nondescriptive sentences in all aphasic subgroups. In the two verbal versions of the Scrambled Story Test, the nonfluent aphasic groups, namely, global and Broca’s aphasics, had numerically higher correlations for the descriptive sentences, whereas the fluent aphasics’ correlations were reversed. With the right-hemisphere controls in the pictorial version, the correlation with comprehension of nondescriptive sentences was numerically higher than with comprehension of descriptive sentences. But in the two verbal versions no striking differences were found. DISCUSSION
Aphasic patients and right-brain-damaged and normal controls were asked to arrange an unordered set of either pictures or sentences into a narrative. Two verbal versions of the target stories were constructed, one with low and one with high linguistic cohesion. The same stories were used in all three versions of the test and the content of single sentences corresponded to that of single pictures. As expected, we found a differential involvement of the two hemispheres with respect to pictures
Note. n = 18. * p c .05. ** p s .Ol.
Global Wernicke Broca Amnesic RH controls
Story X sentence
.61** .69** .55* .21 .26
TABLE 6
.13 .49* .22 -.19 .52*
Nondescriptive Nondescriptive 39 .61** .14 .25 .35
Descriptive .71** A4 .43 - .05 .33
.30 .41 .34 - .Ol .35
.23 .61** .17 .46 .40
Nondescriptive
x
TEST
High-cohesion
COMPREHENSION
Descriptive
STORY TEST AND SENTENCE
Low-cohesion x
BETWEEN PERFORMANCE ON SCRAMBLED
Picture x
CORRELATIONS
Descriptive
SPEARMAN RANK
i? ii E
% u
5 g !a
1.5
PROCESSING OF NARRATIVES TABLE I SPEARMAN
RANK
CORRELATIONS
BETWEEN PERFORMANCE ON SCRAMBLED STORY TEST AND TOKEN TEST (PART III)
Picture X Story X Token Test Global Wemicke Broca Amnesic
Low-cohesion x
Visual
Auditory
Visual
.54* .67** .41 .19
- .36 .12 -.02 - .07
.54* .65** .39 .lO
Auditory .21 .38 .18 .24
High-cohesion x Visual
Auditory
.26 .59** .33 .45
- .21 .37 .18 .38
Note. n = 18.
* p s .05. ** p s .Ol.
and sentences. The differences in performance, however, depended partly on the order in which the three versions of each story occurred during testing. Right-hemisphere patients had significantly more difficulties with the pictorial versions when they occurred before the two corresponding verbal versions. In contrast, patients with Wernicke’s and Broca’s aphasia had significantly fewer difficulties in arranging pictures than sentences when pictures occurred last. The lack of differences with the other orderings could be due to successful transfer from the less to the more impaired mode of processing, i.e., from verbal to pictorial in the right-hemisphere group and from pictorial to verbal in the aphasic groups. No transfer occurred in patients with global aphasia. Pictures were significantly easier to process than sentences in all three orderings. Because of these differences in levels of performance one can not easily conclude that only cognitive factors common to the processing of both pictures and texts are affected in conditions of brain damage. On the contrary, it seems that the ordering of pictures and texts is influenced by different factors. Even with respect to the picture arrangement taskwhere we did not find differences-it does not seem plausible that there is a general intellectual impairment influencing the performance of aphasics and right-hemisphere controls in much the same way. If we were to follow this assumption, it would be difficult to explain why it is that right-hemisphere patients make significantly fewer errors when arranging low-cohesion texts even though these texts exhibit the same coherence features as the cartoon stories and do not allow for much linguistic cuing. It seems more plausible that specific visual-cognitive deficits make it difficult for the right-hemisphere patients to recognize the pictorial cues that are necessary for correct reconstruction of the series of events depicted in the cartoon stories. The distribution of error scores when the lesion site was controlled (cf. Table 4) supports this assumption. Right-hemisphere patients’ with retrorolandic involvement had the most
16
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outstanding difficulties with the picture arrangement version as compared to the two verbal versions. This finding is in agreement with many reports on specific visual-spatial deficits caused by lesions in these areas (Milner, 1974; Sperry, 1974). Whether specific visual-cognitive deficits also caused the difficulties the aphasics had with the pictorial version cannot be decided unequivocally. At first glance it looks as if aphasia had no particular influence on the pictorial processing. However, correlation studies showed that there was a common variation between the Token Test performance and each of the arrangement tasks. This was found only with respect to the visual Token Test performance, not with respect to the auditory one. The auditory version required a greater memory load than the visual version or the three versions of the Scrambled Story Test. In the visual version of the Token Test the written commands remained uncovered until the subjects had finished pointing to the tokens. If written commands are presented only briefly, no differences between auditory and visual mode of presentation are found (Poeck & Hartje, 1979). Thus, the significant correlations between the performances on the Token Test and on the Scrambled Story Test independent of its pictorial or verbal presentation seem to indicate that there is indeed a cognitive and/or linguistic factor that is particularly relevant to aphasia and that influences performance on the linguistic as well as on the nonlinguistic arrangement task. Cohen, Kelter, and Schtifoer (1977) suggest that the poor performance of aphasic patients on the Token Test reflects an impairment in the general analytic capacity which is attributed to the left hemisphere. The degree of linguistic cohesion had no significant influences on the performance of any of the groups. The largest numerical difference between scores on low- and high-cohesion texts was found in the group of normal subjects, which, however, did not reach the level of statistical significance. The smallest number of errors occurred in the high-cohesion version. This can be attributed to the additional microstructure information provided in this version. The brain-damaged groups, however, seem to have relied only on macrostructure information, which was essentially the same in the two verbal versions of the task. An alternative interpretation would be that underlying differences in the processing of the two texts were overridden by other factors such as the overall complexity of contextualization or the impact of redundancy that made up for the greater lexical and syntactic complexity of the high-cohesion versions. The question that remains unanswered by these alternative interpretations is why right-hemisphere patients showed the same pattern of linguistic performance as aphasic patients. In our view, subjects in conditions of brain damage generally rely on macro- and not on microstructure information. In the control test on sentence comprehension two semantic types of
PROCESSING OF NARRATIVES
17
sentences were considered and these presumably induce different cognitive strategies. The sentences in which the reference situation is fully specified allow for a descriptive strategy, i.e., the subjects deduce the reference situation of the sentence by adding up the meaning of its parts. Thus, the pictorial components of the target picture can be matched not only with the meaning of the whole sentence but also with the meaning of its parts. With the nondescriptive sentences, however, a strategy of pragmatic reasoning might prevail. The target picture is more easily identified if subjects first deduce a set of plausible reference situations from the meaning of the whole sentence and then search for the best match among the multiple-choice pictures. Under this assumption of two different cognitive strategies, the results of the correlation studies lead to the following interpretation. In arranging pictures, the underlying strategy of the aphasic patients is mainly descriptive, i.e., decisions on the correct sequencing are based on comparing single pictorial components of the individual pictures. In righthemisphere patients, however, the strategy based on pragmatic expectations is the predominant one. This strategy also seems to play an additional role in patients with Wernicke’s aphasia. In arranging sentences, the Wernicke patients follow predominantly the pragmatic reasoning strategy independently of the degree of cohesion. Patients with global aphasia, however, rely on the descriptive strategy, at least when they are confronted with the noncohesive texts. The correlation values found for the other groups were too low for an interpretation, although the overall pattern is consistent with our distinction between the two strategies. How does this interpretation fit the common view on a functional asymmetry between analytic and holistic processing in the left versus right hemisphere of the normal human brain? This general distinction is reflected in our assumption of a descriptive strategy and a nondescriptive one that is based on pragmatic reasoning. Given a task in which strategies of both types can be applied, it seems that some groups of brain damaged patients adhere “paradoxically” to that type of processing that is specifically impaired. In our study this was most likely the case with the right-hemisphere patients and particularily with the global aphasics, who had extended left-hemisphere impairments. REFERENCES Basso, A., De Renzi, E., Faglioni, P., Scotti, C., & Spinnler, H. 1973. Neoropsychological evidence for the existence of cerebral areas critical to the performance of intelligence tasks. Brain, 96, 715-728. Bay, E. 1960. Zur Methodik der Aphasieuntersuchung. Nervenarzt, 31, 145-154. Bay, E. 1962. Aphasia and non-verbal disorders of language. Brain, 85, 411-425. Cohen, R., Kelter, S., & Schafoer, B. 1977. Zum Einfluss des Sprachverstandnisses auf die Leistungen im Token Test. Zeitschrif fiir Khische Psychologie, 6, 1-14. van Dijk, T. A., & Kintsch, W. 1978. Cognitive psychology and discourse: Recalling and
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summarizing stories. In W. U. Dressler (Ed.), Current trends in textlinguistics. Berlin: de Gruyter. Pp. 61-80. Dressier, W. U. 1973. Einfiihrung in die Textlinguistik. Tubingen: Niemeyer. Fillmore, C. J. 1974. Pragmatics and the description of discourse. In E. J. Fillmore, G. Lakoff, & R. Lakoff (Eds.), Berkeley studies in syntax and semantics. Berkeley: Univ. of California Press. Gabriel, K. R. 1969. Simultaneous test procedures-some theory of multiple comparisons. Annals
of Mathematical
Statistics,
40, 224-250.
Haberlandt, H., & Bingham, G. 1978. Verbs contribute to the coherence of brief narratives: Reading related and unrelated sentence triples. Journal of Verbal Learning and Verbal Behavior,
17, 419-425.
Hatfield, F. M., & Zangwill, 0. L. 1974. Ideation in aphasia: The picture-story method. Neuropsychologia,
12, 389-393.
Haviland, S. E., & Clark, H. H. 1974. What’s new? Acquiring new information as a process in comprehension. Journal of Verbal Learning and Verbal Behavior, 13, 512-521. Kerschensteiner, M., Poeck, K., Huber, W., & Stachowiak, F.-J. 1975. Die Untersuchung auf Aphasie. Aktuelle Neurologie, 2, 151-157. Kertesz, A., & McCabe, P. 1977. Recovery patterns and prognosis in aphasia. Brain, 100, 1-18. Kintsch, W. 1974. The representation of meaning in memory. Hillsdale, NJ: Erlbaum. Kirk, R. E. 1968. Experimental design: Procedures for the behavioral sciences. Belmont, CA: Brooks & Cole. Kossatz, H. 1972. So ein Dackel! 22 Bildergeschichten fiir den Sprachunterricht. Stuttgart: Klett. Lebrun, Y., & Hoops, R. (Eds.). 1974. Intelligence and aphasia. Amsterdam: Swets and Zeitlinger. I Milner, B. 1974. Hemispheric specialization: Scope and limits. In F. 0. Schmitt, & F. G. Worden (Eds.), The neurosciences. Third study program. Cambridge, MA: MIT Press. Pp. 75-89. Orgass, B. 1976. Eine Revision des Token Tests. Part I & II. Diagnostica, 22, 70-87, 141-156. Orgass, B., Hartje, W., Kerschensteiner, M., & Poeck, K. 1972. Aphasie und nichtsprachliche Intelligenz. Nervenarzt, 43, 623-627. Plauen, E. 0. 1949. 1951. 1952. Vater und Sohn. Neue Ausgabe. Konstanz: Siidverlag. Vols. l-3. Poeck, K., Kerschensteiner, M., Stachowiak, F.-J., & Huber, W. 1975. Die Aphasien. Aktuelle Neurologie, 2, 159-169. Poeck, K., & Hartje, W. 1979. Performance of aphasic patients in visual versus auditory presentation of the Token Test: Demonstration of a supramodal deficit. In F. Boller & M. Dennis (Eds.), Auditory comprehension. Clinical and experimental studies with the Token Test. New York: Academic Press. Pp. 107-113. Sperry, R. W. 1974. Lateral specialization in the surgically separated hemispheres. In F. 0. Schmitt, & F. G. Worden. (Eds.), The neurosciences. Third study program. Cambridge, MA: MIT Press, Pp. 5-19. Stachowiak, F.-J., Huber, W., Poeck, K., & Kerschensteiner, M. 1977. Text comprehension in aphasia. Brain and Language, 4, 177-195. Veroff, A. E. 1978. A structural determinant of hemispheric processing of pictorial material. Brain and Language, 5, 139-148. Vipond, D. 1980. Micro- and macroprocesses in text comprehension. Journal of Verbal Learning
and Verbal Behavior,
19, 276-296.
Zangwill, 0. L. 1978. The relation of nonverbal cognitive functions to aphasia. In E. H. Lenneberg & E. Lenneberg (Eds.), Foundations of language development. New York: Academic Press. Vol. 2, pp. 95-104.
AND
LANGUAGE
16, l-18
(1982)
Linguistic and Nonlinguistic Processing of Narratives in Aphasia WALTER
HUBER
AND JOCHEN GLEBER
Rheinisch-Westftilische Technische Hochschule Aachen A scrambled Story Test was given to four subgroups of aphasic patients and to one group each of right-hemisphere-damaged patients and of normal controls. Subjects were asked to construct narratives from an unordered set of pictures and from unordered sets of corresponding sentences. Two verbal versions were distinguished, one with high and one with low linguistic cohesion among sentences. As expected, we found interactions between aphasic and nonaphasic behavior, such that aphasic patients made relatively more errors on the verbal versions and right-hemisphere patients on the pictorial version. High versus low linguistic cohesion, however, had no differential impact. It is concluded that brain-damaged patients when processing texts generally rely on macro- rather than on microstructure information. Furthermore, two control tests were administered: the Token Test and a sentence-to-picture matching task with either descriptive or nondescriptive stimulus sentences. Various patterns of correlation between these control tests and the Scrambled Story Test were found. The findings are interpreted in terms of a differential involvement of descriptive versus pragmatic processing strategies.
INTRODUCTION In general linguistics, a discourse or text is viewed not just as an enumeration of sentences, but is defined and described by properties of its own on the stylistic and/or syntactic level as well as on the semantic level. The most prominent semantic characteristics of texts is the overlap between the propositional structures of its sentences. The degree of propositional overlap determines the coherence of a text (van Dijk & Kintsch, 1978). There are many lexical and syntactic devices that make evident the coherence of the situations described by a text. Among these devices are coreference relations, attributive and adverbial specifications, The authors wish to thank Klaus Willmes for the statistical evaluation of the data and Klaus Poeck, Dorothea Weniger, and Ria de Bleser for their many helpful suggestions on carrying through this study and on preparing this paper. Reprint requests should be addressed to Dr. Walter Huber, Abt. Neurologie, RWTH Aachen, Goethestr. 27-29, 5100 Aachen, Federal Republic of Germany.
0093-934X/82/030001-18$02.00/0 Copyright 0 1982 by Academic Press, Inc. All rights of reproduction in any form reserved.
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changes in word order, paraphrases, repetitions, and the like. These devices all contribute to the linguistic cohesion of a particular text (Dressler, 1973). Some of the experimental work in psycholinguistics gives evidence to the point that the processing of texts depends more on semantic than on stylistic or syntactic factors. For example, Kintsch (1974) demonstrated that high versus low syntactic complexity of texts has no impact on the accuracy of recall. On the other hand, Haberlandt and Bingham (1978) showed in a reading task study that the degree of semantic and logical coherence influences the processing of texts. It must be stressed, however, that semantic coherence of a text cannot be strictly kept apart from the stylistic and syntactic cohesion of a text. Haviland and Clark (1974) argue that new information in a text can be more easily understood if the new information is linguistically tied to “given” information, i.e., information mentioned before by means of linguistic cohesion devices. Furthermore, the coherence of a text does not depend on its propositional structure alone. Pragmatic factors are also involved. The hearer incorporates information provided by the situation in which a text occurs and to which it refers. This information will be mediated by the hearer’s experiences, expectations, and so on. Thus, the hearer is involved in both verbal and situational contextualization when he is confronted with a text (Fillmore, 1974). By contextualization we mean general cognitive processes, such as inference, deduction, and problem solving, that supplement the hearer’s lexical and grammatical knowledge and are the means by which he will eventually reconstruct the series of events described in a particular text. Contextualization is, of course, not restricted to linguistic material. For example, when we look at cartoon stories we also make contextualizations. But instead of observing lexical and syntactic cohesion devices we might pick out various pictorial cues which make it easier to comprehend the series of events depicted. So far, only a few studies have dealt with contextualization in conditions of brain damage. In a text-to-picture matching task, Stachowiak, Huber, Poeck, and Kerschensteiner (1977) found that aphasic patients made only insignificantly more errors than right-hemisphere-damaged and normal controls. In a picture arrangement task, Veroff (1978) studied two features of pictorial contextualization. Subjects had to recognize changes of category in the development of an organism (e.g., a tadpole growing into a frog) and they had to recognize changes of place in the movement of an object (e.g., a golf ball rolling toward the hole). Veroff’s results indicate the possibility of a differential hemispheric involvement. Her three patients with large left-hemisphere lesions had more difficulties with change of category sequences than her six right-hemisphere-damaged patients, who made more errors on the change of place sequences. A specific involvement of the right hemisphere in visual-spatial tasks
PROCESSING
OF NARRATIVES
3
was demonstrated in many clinical studies (for review, cf. Milner, 1974; Sperry, 1974). Processing of more complex visual information, however, seems to be affected by lesions in both hemispheres, especially in the retrorolandic areas (Orgass, Hartje, Kerschensteiner, & Poeck, 1972; Basso, DeRenzi, Faglioni, Scotti, & Spinnler, 1973). With respect to the performances in the picture arrangement task of the Hamburg Wechseler Intelligence Scales, Orgass et al . (1972) did not find significant differences between aphasic patients and right-hemisphere controls. This finding might reflect either a general intellectual deficit in verbal mediation or in visual-spatial processing in either one of the two groups. It is an unresolved question whether there are common cognitive strategies underlying contextualization in both the pictorial and the linguistic mode of presentation of a narrative. In general, it is questionable whether there is a common cognitive basis to language and thought and what this basis might be. With respect to aphasia two alternative positions have been taken. On the one hand it has been claimed that the linguistic disturbance is a consequence of an underlying cognitive impairment. Such a position was taken most explicitly in the work of Bay (e.g., 1962). According to Bay (1960), the poor performance of aphasic patients in rendering verbally what they had seen in a cartoon story is caused either because of their inability to contextualize the pictorial information or because they cannot comprehend specifically the humor which is expressed by these stories. On the other hand, opponents of this view hold that aphasia is primarily characterized by specific disturbances of elementary lexical and syntactic abilities. An impairment of nonlinguistic cognitive abilities does not necessarily coincide with the occurrence of aphasia (cf. Zangwill, 1978; Lebrun & Hoops, 1974). From this view point, the poor performance of aphasic patients that was reported by Bay would be due to linguistic difficulties in their expressive verbal behavior. Hatfield and Zangwill (1974) reported of a patient with severe and persistent aphasia who was substantially unimpaired when he was asked to communicate a sequence of events by drawing in spite of severe defects in his spoken and written expression. From data like these it seems that aphasia cannot be reduced to a general intellectual impairment. However, more conclusive evidence is lacking. When investigating these questions, one has to make sure that the same or at least similar cognitive problems have to be solved in a nonlinguistic and in a linguistic mode of presentation. It was within this context of questions that we had aphasic and nonaphasic brain-damaged patients as well as normal controls construct narratives from an unordered set of pictures and from an unordered set of corresponding sentences. If, in such tasks, aphasic patients fail in both modes of presentation and if they are inferior to the nonaphasic controls even in the
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nonlinguistic mode, then the view that aphasia is an outcome of a specific intellectual deficit rather than a specific linguistic one, could not be refuted. But if one believes that aphasia is mainly a specific linguistic deficit then one should, of course, expect that clear differences between aphasics and controls will be found in the linguistic mode of presentation, but no differences in the nonlinguistic mode. If one, furthermore, doubts that the apparent common basis of language and thought will be specifically affected in conditions of brain damage, then one should expect both right-hemisphere and aphasic patients to show a clear difference between verbal and nonverbal processing, but in reverse directions, such that in right-hemisphere patniets’ nonverbal processing is more affected than verbal processing. In addition, we wanted to find out whether the linguistic processing of texts in such an arrangement task depends more on macro- than on microstructure information. The difference was controlled by two versions of the sentence arrangement task, one with low and one with high linguistic cohesion. If subjects predominantly rely on the core sequence of events, i.e., on the macropropositions of the text, then their level of performance should be substantially unchanged when they are provided with versions of higher cohesion, i.e., with additional microstructure information. This expectation follows from a previous investigation of text comprehension in aphasia (Stachowiak et al., 1977), as well as from a study of normal subjects who were asked to read and recall written texts (Vipond, 1980). MATERIALS AND METHODS Subjects Four groups of aphasic patients, a group of right-brain-damaged, and a group of normal controls were studied. Each group included 18 subjects. The aphasic groups were samples of the four major clinical syndromes of aphasia: global, Wemicke’s, Broca’s, and amnesic aphasia. Classification of the syndrome was based on standardized clinical examination (Kerschensteiner, Poeck, Huber, & Stachowiak, 1975; Poeck, Kerschensteiner, Stachowiak, 8~ Huber, 1975). The following features of spontaneous speech were taken as main characteristics: nonfluent, highly automatized speech for global aphasia; fluent, paragrammatic speech, semantic, and/or phonemic paraphasias for Wemicke’s aphasia; nonfluent agrammatic speech and phonemic paraphasias for Broca’s aphasia; word-finding difficulties for amnesic aphasia. In most aphasic and in all brain-damaged control patients, the lesion site was assessed by evaluation of CT scans or EEG recordings. The normal controls were also patients from the neurological wards having no signs of an involvement of the central nervous system. The distribution of age, sex, etiology, duration, and site of lesion is summarized in Table 1. The aphasic subjects were either in- or out-patients in the course of speech therapy. Therefore age and duration varied considerably among the aphasic subgroups. Similar differences were reported in other clinical studies (e.g., Kertesz & McCabe 1977). Educational and occupational level, however, was quite comparable among the groups. All subjects had finished elementary school and no more than two subjects of each group had full academic training.
8 5 5 7 11 6
Female
10 13 13 11 7 12
Male
a p: prerolandic, r: retrorolandic. b RH: right hemisphere; N: normal.
Global Wemicke Broca Amnesic RI-I control2 N controls*
Group (n = 18)
Sex
48.6 58.4 43.0 47.3 48.2 42.3
Mean age tye=s) 15 16 15 15 13 -
Vast
-
3 2 3 3 5
Others
Etiology
31.1 10.6 18.8 3.9 13.1 -
Mean duration (months)
TABLE 1 SAMPLECHARACTERISTICS
1 1 11 6 7 -
P
0 11 0 7 5 -
r
17 1 3 2 6 -
p+r
Site of lesion”
-
0 5 4 3 0
Unknown
% “c E
5
%
8 z 5 Q
g
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HUBER AND GLEBER
Material Scrambled Story Test. The test consisted of one pictorial and two verbal versions. In all three versions, the unordered elements of a story-pictures or sentences-had to be rearranged into the correct order. The task was demonstrated by one example for the pictorial and one example for the verbal versions. The subjects were told that they had to consider all presented pictures or sentences for a correct solution, there was no time limit imposed and the patients were asked to indicate when they had finished. Patients who did not comprehend the task on demonstration were excluded. This was the case with five additionally seen patients, four patients with global and one with Wernicke’s aphasia. A total of nine little known cartoon stories of six pictures each were selected from Plauen (1949, 1951, 1952) and from Kossatz (1972). They were similar in style and depicted scenes from everyday life featuring a man and his little son or his dog. An example of the cartoon stories is given in Fig. 1. Two written versions of each story were constructed, one with high and one with low linguistic cohesion as illustrated in Table 2. In both verbal versions, each of the six sentences corresponded to one picture of the original cartoon story. In the low-cohesion version, the syntactic structure of the sentences was as simple as possible and only familiar content words were used. No attributive or adverbial specifications of the events described were given. Thus we obtained rather nonredundant texts. The only cohesion devices we used were repetition of content words and variation in the indefinite and definite articles, marking new versus old information. In the high-cohesion version, the sentences were characterized by complex syntactic structures and many attributive and adverbial specifications. The single sentences were interconnected by stylistic and semantic devices, such as topicalization of constituents and embedding of temporal or causal clauses. The two verbal versions differed in length. In the low-cohesion version the mean number of words per sentence was 6.8 with a range from 3 to 11, and in the high-cohesion version 15.5 with a range from 9 to 21. In both verbal versions the core
FIG. 1. Example of the pictorial version of the Scrambled Story Test (cartoon story taken from Kossatz, 1972).
PROCESSING OF NARRATIVES
7
TABLE 2 EXAMPLES OF THE Two VERBAL VERSIONSOF THE SCRAMBLEDSTORY TEST(TRANSLATED FROM THE ORIGINAL GERMAN)
1. Low linguistic cohesion (1) A man is hit on the head by a flower pot (2) The man scolds the woman on the balcony (3) The man and his dog enter the house (4) The man knocks on the apartment door (5) The woman gives the dog a bone (6) The man kisses the woman’s hand 2. High linguistic cohesion (1) While walking down the street with his dog, an elderly gentleman was suddenly hit on the head by a flower pot falling from a balcony (2) Both master and dog scolded the culprit on the balcony angrily at the top of their voices (3) In order to teach him a lesson, they entered the house purposefully (4) They stopped on the second floor and the gentleman knocked on the apartment door with his cane (5) An elderly lady opened the door and, full of sympathy, comforted the dog with a bone (6) This made the elderly gentleman feel good and he gallantly kissed the lady’s hand
sequence of events was exactly the same and was based on the original cartoon story. In other words, in all three versions of each narrative we tried to keep the logical and pragmatic coherence features (the “macrostructure”) as constant as possible, but varied systematically the propositional “microstructure” of the two written versions of the narrative. This difference in microstructure is reflected by high versus low linguistic cohesion. The size of stimulus pictures was 11 x 8 cm. The unordered set of pictures was given in a single row as in the picture arrangement task of the Wechsler Intelligence Scale. The stimulus sentences were printed in capital letters on index cards with a size of 21 x 4 cm. The unordered set of sentence cards was represented and had to be rearranged in a vertical array. Visible only to the investigator, the stimulus order was specified by the alphabetic letters A, B, C, D, E, F, that were printed on the back of the stimulus cards. In all items, the number of elements that had to be reordered for a correct solution was 3 or 4. With incorrect reactions, the degree of deviation was estimated by means of an error score: proceeding in the direction of the correct order, we counted the minimal number of permutations of single elements or of chains of elements that were necessary to yield the correct solution. The correct order was also marked on the back of the stimulus cards by numbers from 1 to 6. False sequences like l-3-4-2-5-6, l-2-4-3-5-6, 2-l-3-4-5-6, 3-4-l-2-5-6, 4-5-6-l-2-3, etc. would score as 1, 2-l-4-5-3-6 as 2, 2-l- 5-4-3-6 as 3, and so on. The maximum possible score of 5 would result if the correct sequence were completely reversed to 6-5-4-3-2-l. This reaction occurred only once, namely, in the pictorial version of the task, and was counted as correct, as the patient indicated that the sequence should be read from right to left. As an alternative to this kind of scoring, permutations of chains of elements could be counted as multiple permutations of single elements. But this seemed psychologically less plausible. For example, a false sequence like 4-5-6-l-2-3 scores as 1 in our system, but would score as 3 in the alternative system. Sentence Comprehension Test. Subjects were asked to silently read a sentence. fmmediately afterward a multiple-choice set of four pictures was presented. The subject had to point to the one picture that corresponded best to the meaning of the sentence. We distinguished two sets of stimulus sentences. In the one set, nondescriptive sentences like
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HUBER AND GLEBER
“He is going to be put in jail” were given. The set of multiple choice pictures used for this particular sentence is illustrated in Fig. 2. The appropriate reference situation is depicted on the bottom left. Confusion would occur if the subject just took the lexical meaning of a single key word like “jail” in the given example. Then, subjects would most likely point to the distractor picture, the one on the top right of Fig. 2. The distractor picture represented a situation which pragmatically precedes or follows the reference situation of the target sentence. Using the same set of pictures but in different order, a second set of sentences was constructed. These were fully descriptive sentences like “The policeman who caught a criminal is now forcing him to hold back his arms and is searching him for weapons.” In this type of sentences the target situation is fully specified and described in redundant form. There were 10 items for each set of sentences. The total of 20 items was split into two blocks, such that the two sentence types were equally distributed and only one of the two sets of multiple choice pictures occurred within one block. The order of sentence types was varied across the 10 items of each block. It was hypothesized that the nondescriptive sentences would require more situational contextualization than the descriptive ones and that they therefore should be more closely related to the text with low rather than high linguistic cohesion. Token Test. In order to control the possible influence of reading performance, part III of the Token Test in the revised German version (Orgass, 1976) was given in two modes of presentation: one auditory and one visual. As in the text-sorting task, there was no time limit on reading, and the written instructions remained uncovered until the subject had finished pointing to the tokens.
t
d
FIG. 2. Example of the multiple-choice pictures used in the Sentence Comprehension Test.
9
PROCESSING OF NARRATIVES
Procedure The 27 items of the Scrambled Story Test were divided into three blocks. Within each block, each of the nine stories occurred either in the pictorial version or in one of the two written versions. Thus, each mode of presentation occurred three times within each block, but each story only once. In order to control possible position effects, the six possible combinations in ordering the three blocks were varied from patient to patient. Each order of blocks was given to three of the 18 subjects in each group. This procedure made it possible to detect differences in performance depending on whether the pictorial version came first, second, or last with respect to the two verbal versions of the same story. The blocks of the Scrambled Story Test and of the two control tests were given in the following order: Auditory Token Test (10 items), Story Test (9 items), Sentence Test (10 items), Story Test (9 items), Sentence Test (10 items), Story Test (9 items), Visual Token Test (10 items). In contrast to the Story Test, the order of blocks of the two control tests remained the same for all subjects.
RESULTS Scrambled
Story Test
The mean error scores and the standard deviations in the nine items of each of the three versions of the test are given in Table 3. The error scores of one item count the number of segments out of six that were placed into a wrong position. The number of misplaced segments given in the stimulus sequence of one item was either 3 or 4, and 31 in all 9 items. Error scores substantially lower than this were found for all groups in the pictorial version, which indicates that their performances went in the direction of the correct solution. The most difficulties occurred with the two verbal versions in the two most impaired aphasic groups, viz., patients with global and Wemicke’s aphasia. They performed nearly at chance level. As expected, there are numerical interactions between the pictorial TABLE 3 MEANS
AND STANDARD DEVIATIONS OF ERROR SCORES IN THE THREE VERSIONS OF THE SCRAMBLED STORY TEST (NINE ITEMS EACH)
Pictorial version
Verbal versions Low cohesion
n = 18 Global Wemicke Broca Amnesic RH controls N controls
High cohesion
Mean
SD
Mean
SD
Mean
SD
13.1 15.6 8.6 7.6 11.8 5.1
(6.2)
20.7 19.6” 11.6 7.7 7.2 3.3
(3.9) (7.2)
20.3 19.6” 11.0 6.0 7.0 1.6
(4.8) (7.9) (8.4) (3.9)
(7.3)
(6.2) (4.1) (7.8) (3.2)
(8.2) (4.1)
(6.6) (2.5)
(6.8) (1.8)
’ No substantial reduction of permutations when compared to the total number of permutations given in all nine stimulus sequences (N = 31); binomial tables, a = 1%.
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and the two verbal modes of presentation. The nonaphasic controls had more difficulties with the arrangement of pictures than with sentences. The reverse tendency holds true for the patients with global, Wernicke’s, and Broca’s aphasia. Differences between the two verbal versions seem to exist only in amnesic aphasics and normal controls. In both groups, the high-cohesion texts caused the least difficulties. The data were analyzed by univariate analysis of variance using a split-plot design. Because of heterogeneous variance-covariance matrices (x2 = 80, 7 > x2 (30, 90%) = 40, 3) we made a correction for the degrees of freedom (Kirk, 1968). We found a significant interaction between the group factor and the task factor (F = 11.94 > F(10 corrected to 5, 204, 95%) = 2.26). Significant simple main effects were found for the group factor in all three versions of the task and for the task factor with respect to global and Wernicke’s aphasics and to right-hemisphere controls. In Broca aphasics and normal controls the F values were close to being significant (Broca’s: F = 5.30, Normals: F = 5.26; F(2 corrected to 1, 204,99%) = 6.76; F (uncorrected) = 4.71). No influence was found for amnesic aphasics (F = 1.49). Succeeding pairwise comparisons using simultaneous test procedures (Gabriel, 1969) yielded the following result: (1) Pairwise comparisons between groups Pictorial version WE GL RH Verbial versions Low cohesion High cohesion
BR
AM
NC
GL
WE
BR
AM
RH
NC
GL
WE
BR
AM
RH
NC
(2) Pairwise comparisons between modes of presentation PICT LOW Global aphasia Wernicke’s
PICT
LOW
HIGH HIGH
Broca’s
PICT
HIGH
LOW
Amnesic RH controls Normal controls
PICT PICT PICT
HIGH LOW LOW
LOW
HIGH HIGH Significant differences were found only between those groups/modes which are not connected by an underline. Between groups, the differences found in the verbal versions were more often significant than those found in the pictorial version. This is mainly due to the much larger number of difficulties that patients with global and Wernicke’s aphasia had with both verbal versions. When arranging sentences into narratives, all the aphasic subgroups-with the
PROCESSING
OF NARRATIVES
11
exception of amnesic aphasics-had significantly more difficulties than normal controls, which is not surprising at all. In arranging pictures, significant differences were found between patients with Wernicke’s aphasia, who had the largest amount of difficulties, and all other groups except global aphasics and right-hemisphere controls. Furthermore, the performance of patients with global aphasia was significantly worse than that of the normal controls. Significant differences between the processing of the pictorial and of each of the two verbal modes were found for global aphasics and right-hemisphere controls. In none of the, groups, however, did we find significant differences between the processing of the two verbal versions of the test. This finding was quite unexpected. In order to control the possible effects of differences in order of presentation, the error scores of each patient were divided into three portions, depending on whether the pictorial version was presented first, second, or third. For each ordering, a separate analysis of variance was carried through, calling for a reduction of the alpha level from 5 to 1%. Again, we found significant interactions between the group factor and the task factor for each type of sequence. After assessing significant simple main effects, pairwise comparisons of differences between pictures and texts were carried through. We obtained the following differences (P = pictures; T = text with either low or high cohesion): Types of sequence
Groups Global Wernicke’s Broca’s Amnesic RH controls
P-T-T P-T-T P-T-T P-T-T P-T-T
T-P-T T-P-T T-P-T T-P-T T-P-T
T-T-P T-T-P T-T-P T-T-P T-T-P
Again an underline shows that no significant difference was found between the modes of presentation thus connected. The normal controls were not considered in this analysis because the variations in their error scores were too low. The global aphasics had significantly greater difficulties in arranging sentences than pictures in each type of sequence. For Wernicke’s and Broca’s aphasics, however, significant differences were found only when the pictorial version of the narrative was presented last. In contrast, the right-hemisphere patients had significantly greater difficulties with pictures than with texts only when the pictures were presented first. Thus, the general finding of an interaction between pictures and texts with respect to aphasic versus right-hemisphere patients depends partly on the order in which pictures and texts were presented. With respect to single segments, we found that neither type nor position significantly influenced performance. First, we ascertained that type and
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HUBER AND GLEBER
position of incorrectly arranged single segments were independent features (x2 test), second, that segments l-3 in contrast to segments 4-6 of the target sequence did not yield greater or smaller frequencies of errors; and third, that the errors occurred as frequently in the first three positions of the arranged sequence as in the last three positions (Wilcoxon-test, two-tailed). Thus, the errors were almost equally distributed across individual segments and positions. Furthermore, we tried to control the influence of lesion site in the right-hemisphere patient group on the processing of pictures versus sentences. The mean error scores in Table 4 indicate that patients with retrorolandic lesions had-as expected-the largest number of difficulties with the pictorial version of the task. Because of the small sample sizes, no statistical analysis was carried through. Control Tests In the sentence comprehension task the descriptive sentences were, as expected, less difficult than the nondescriptive ones. This can be seen from the mean numbers of incorrect reactions given in Table 5. Normal controls made no errors in either version of the task. Applying analysis of variance, we found significant differences between the processing of the two types of sentences for each of the groups. As in the Scrambled Story Test, we did not find reliable differences between the right-hemisphere controls and the two less impaired aphasic groups, namely the patients with Broca’s and amnesic aphasia. Only with nondescriptive sentences was the distractor picture chosen-as expected-more often than by chance. This was true for all aphasic groups (binominal test, (Y = 1%). The mean errors of the two versions of part III of the Token Test are given in Table 5 as well. The visual version was easier to solve in all aphasic groups, although we found no significant differences when apTABLE 4 DISTRIBUTION OF ERROR SCORES IN THE SCRAMBLED STORY TEST (NINE ITEMS) AMONG RIGHT-HEMISPHERE CONTROLS WITH RESPECT TO SITE OF LESION
Verbal versions RH controls Prerolandic n=7 retrorolandic n=5 Pre + retrorolandic n=6
M Md M Md M Md
Pictorial version
Low cohesion
High cohesion
7.4 3.0 (l-23) 17.0 18.0 (6-24) 12.7 11.o (5-20)
4.4 3.0 (O-14) 7.4 6.0 (3-13) 10.3 6.5 (l-24)
4.3 3.0 (O-16) 7.2 7.0 (3-12) 10.0 7.5 (O-23)
13
PROCESSING OF NARRATIVES TABLE 5 MEANS AND STANDARD DEVIATIONS OF INCORRECTREACTIONS IN THE CONTROLTESTS (10 ITEMS EACH)
Token Test
Sentence comprehension test Descriptive n = 18 Global Wemicke Broca Amnesic RH controls
Nondescriptive
Visual
Auditory
Mean
SD
Mean
SD
Mean
SD
Mean
SD
1.8 1.4 0.4 0.3 0.3
(2.1) (2.1) (1.0) (0.6) (0.5)
6.0 4.6 3.1 2.0 2.2
(2.4) (2.5) (2.1) (0.6) (0.5)
5.2 5.6 1.6 0.2 0.0
(3.7) (4.1) (2.7) (0.4) (-1
8.7 6.8 3.7 1.8 0.0
(1.8) (3.3) (3.5) (3.1) C-1
plying analysis of variance. Right-hemisphere and normal controls were not included because they did not make any errors in either version of the test. The relationship between the performance on both control tests and the Scrambled Story Test was assessedby correlation studies. The results are given in Table 6 and 7. With respect to the Token Test performance (cf. Table 7) high correlations were found only for the visual version. Rather surprisingly, the correlations for picture arranging were as high as those for sentence arranging. Comparing the performance in the Sentence Comprehension Test and in the Scrambled Story Test (cf. Table 6), we found the following patterns. In the pictorial version, the correlations for comprehending the descriptive sentences were numerically higher than for the nondescriptive sentences in all aphasic subgroups. In the two verbal versions of the Scrambled Story Test, the nonfluent aphasic groups, namely, global and Broca’s aphasics, had numerically higher correlations for the descriptive sentences, whereas the fluent aphasics’ correlations were reversed. With the right-hemisphere controls in the pictorial version, the correlation with comprehension of nondescriptive sentences was numerically higher than with comprehension of descriptive sentences. But in the two verbal versions no striking differences were found. DISCUSSION
Aphasic patients and right-brain-damaged and normal controls were asked to arrange an unordered set of either pictures or sentences into a narrative. Two verbal versions of the target stories were constructed, one with low and one with high linguistic cohesion. The same stories were used in all three versions of the test and the content of single sentences corresponded to that of single pictures. As expected, we found a differential involvement of the two hemispheres with respect to pictures
Note. n = 18. * p c .05. ** p s .Ol.
Global Wernicke Broca Amnesic RH controls
Story X sentence
.61** .69** .55* .21 .26
TABLE 6
.13 .49* .22 -.19 .52*
Nondescriptive Nondescriptive 39 .61** .14 .25 .35
Descriptive .71** A4 .43 - .05 .33
.30 .41 .34 - .Ol .35
.23 .61** .17 .46 .40
Nondescriptive
x
TEST
High-cohesion
COMPREHENSION
Descriptive
STORY TEST AND SENTENCE
Low-cohesion x
BETWEEN PERFORMANCE ON SCRAMBLED
Picture x
CORRELATIONS
Descriptive
SPEARMAN RANK
i? ii E
% u
5 g !a
1.5
PROCESSING OF NARRATIVES TABLE I SPEARMAN
RANK
CORRELATIONS
BETWEEN PERFORMANCE ON SCRAMBLED STORY TEST AND TOKEN TEST (PART III)
Picture X Story X Token Test Global Wemicke Broca Amnesic
Low-cohesion x
Visual
Auditory
Visual
.54* .67** .41 .19
- .36 .12 -.02 - .07
.54* .65** .39 .lO
Auditory .21 .38 .18 .24
High-cohesion x Visual
Auditory
.26 .59** .33 .45
- .21 .37 .18 .38
Note. n = 18.
* p s .05. ** p s .Ol.
and sentences. The differences in performance, however, depended partly on the order in which the three versions of each story occurred during testing. Right-hemisphere patients had significantly more difficulties with the pictorial versions when they occurred before the two corresponding verbal versions. In contrast, patients with Wernicke’s and Broca’s aphasia had significantly fewer difficulties in arranging pictures than sentences when pictures occurred last. The lack of differences with the other orderings could be due to successful transfer from the less to the more impaired mode of processing, i.e., from verbal to pictorial in the right-hemisphere group and from pictorial to verbal in the aphasic groups. No transfer occurred in patients with global aphasia. Pictures were significantly easier to process than sentences in all three orderings. Because of these differences in levels of performance one can not easily conclude that only cognitive factors common to the processing of both pictures and texts are affected in conditions of brain damage. On the contrary, it seems that the ordering of pictures and texts is influenced by different factors. Even with respect to the picture arrangement taskwhere we did not find differences-it does not seem plausible that there is a general intellectual impairment influencing the performance of aphasics and right-hemisphere controls in much the same way. If we were to follow this assumption, it would be difficult to explain why it is that right-hemisphere patients make significantly fewer errors when arranging low-cohesion texts even though these texts exhibit the same coherence features as the cartoon stories and do not allow for much linguistic cuing. It seems more plausible that specific visual-cognitive deficits make it difficult for the right-hemisphere patients to recognize the pictorial cues that are necessary for correct reconstruction of the series of events depicted in the cartoon stories. The distribution of error scores when the lesion site was controlled (cf. Table 4) supports this assumption. Right-hemisphere patients’ with retrorolandic involvement had the most
16
HUBER
AND
GLEBER
outstanding difficulties with the picture arrangement version as compared to the two verbal versions. This finding is in agreement with many reports on specific visual-spatial deficits caused by lesions in these areas (Milner, 1974; Sperry, 1974). Whether specific visual-cognitive deficits also caused the difficulties the aphasics had with the pictorial version cannot be decided unequivocally. At first glance it looks as if aphasia had no particular influence on the pictorial processing. However, correlation studies showed that there was a common variation between the Token Test performance and each of the arrangement tasks. This was found only with respect to the visual Token Test performance, not with respect to the auditory one. The auditory version required a greater memory load than the visual version or the three versions of the Scrambled Story Test. In the visual version of the Token Test the written commands remained uncovered until the subjects had finished pointing to the tokens. If written commands are presented only briefly, no differences between auditory and visual mode of presentation are found (Poeck & Hartje, 1979). Thus, the significant correlations between the performances on the Token Test and on the Scrambled Story Test independent of its pictorial or verbal presentation seem to indicate that there is indeed a cognitive and/or linguistic factor that is particularly relevant to aphasia and that influences performance on the linguistic as well as on the nonlinguistic arrangement task. Cohen, Kelter, and Schtifoer (1977) suggest that the poor performance of aphasic patients on the Token Test reflects an impairment in the general analytic capacity which is attributed to the left hemisphere. The degree of linguistic cohesion had no significant influences on the performance of any of the groups. The largest numerical difference between scores on low- and high-cohesion texts was found in the group of normal subjects, which, however, did not reach the level of statistical significance. The smallest number of errors occurred in the high-cohesion version. This can be attributed to the additional microstructure information provided in this version. The brain-damaged groups, however, seem to have relied only on macrostructure information, which was essentially the same in the two verbal versions of the task. An alternative interpretation would be that underlying differences in the processing of the two texts were overridden by other factors such as the overall complexity of contextualization or the impact of redundancy that made up for the greater lexical and syntactic complexity of the high-cohesion versions. The question that remains unanswered by these alternative interpretations is why right-hemisphere patients showed the same pattern of linguistic performance as aphasic patients. In our view, subjects in conditions of brain damage generally rely on macro- and not on microstructure information. In the control test on sentence comprehension two semantic types of
PROCESSING OF NARRATIVES
17
sentences were considered and these presumably induce different cognitive strategies. The sentences in which the reference situation is fully specified allow for a descriptive strategy, i.e., the subjects deduce the reference situation of the sentence by adding up the meaning of its parts. Thus, the pictorial components of the target picture can be matched not only with the meaning of the whole sentence but also with the meaning of its parts. With the nondescriptive sentences, however, a strategy of pragmatic reasoning might prevail. The target picture is more easily identified if subjects first deduce a set of plausible reference situations from the meaning of the whole sentence and then search for the best match among the multiple-choice pictures. Under this assumption of two different cognitive strategies, the results of the correlation studies lead to the following interpretation. In arranging pictures, the underlying strategy of the aphasic patients is mainly descriptive, i.e., decisions on the correct sequencing are based on comparing single pictorial components of the individual pictures. In righthemisphere patients, however, the strategy based on pragmatic expectations is the predominant one. This strategy also seems to play an additional role in patients with Wernicke’s aphasia. In arranging sentences, the Wernicke patients follow predominantly the pragmatic reasoning strategy independently of the degree of cohesion. Patients with global aphasia, however, rely on the descriptive strategy, at least when they are confronted with the noncohesive texts. The correlation values found for the other groups were too low for an interpretation, although the overall pattern is consistent with our distinction between the two strategies. How does this interpretation fit the common view on a functional asymmetry between analytic and holistic processing in the left versus right hemisphere of the normal human brain? This general distinction is reflected in our assumption of a descriptive strategy and a nondescriptive one that is based on pragmatic reasoning. Given a task in which strategies of both types can be applied, it seems that some groups of brain damaged patients adhere “paradoxically” to that type of processing that is specifically impaired. In our study this was most likely the case with the right-hemisphere patients and particularily with the global aphasics, who had extended left-hemisphere impairments. REFERENCES Basso, A., De Renzi, E., Faglioni, P., Scotti, C., & Spinnler, H. 1973. Neoropsychological evidence for the existence of cerebral areas critical to the performance of intelligence tasks. Brain, 96, 715-728. Bay, E. 1960. Zur Methodik der Aphasieuntersuchung. Nervenarzt, 31, 145-154. Bay, E. 1962. Aphasia and non-verbal disorders of language. Brain, 85, 411-425. Cohen, R., Kelter, S., & Schafoer, B. 1977. Zum Einfluss des Sprachverstandnisses auf die Leistungen im Token Test. Zeitschrif fiir Khische Psychologie, 6, 1-14. van Dijk, T. A., & Kintsch, W. 1978. Cognitive psychology and discourse: Recalling and
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