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Grammatical Intuitions of Aphasic Patients Sensitivity to Functors
NOTE
GRAMMATICAL INTUITIONS OF APHASIC PATIENTS: SENSITIVITY TO FUNCTORS' E. B. Zurif, E. Green, A. Caramazza and C. Goodenough (Boston University School of Medicine, Boston Veterans Administration Hospital, The John Hopkins University and Universite de Quebec a Montreal)
Routine clinical examinations generally suggest that damage to the frontal area in the left hemisphere - Broca's area - disrupts the ability of patients to produce speech much more than their ability to comprehend. Such patients - Broca's aphasics - often seem to fully understand commands and questions and appear to know what they want to say, yet can only produce short, labored, agrammatic utterances. Like telegrams, these utterances are characterized by the relative omission of bound and unbound grammatical morphemes, or functors, and by a corresponding reliance on content words. This speech pattern and the apparent discrepancy between output and comprehension have been interpreted by some as evidence of preserved language competence in Broca's aphasia (Weigl and Bierwisch, 1970; Lenneberg, 1973; Locke, Caplan and Kellar, 1973). In this view, the patient's tacit knowledge of his language is considered spared, and his agrammatism, simply an economizing measure to circumvent articulatory problems. Evidence that we have recently gained from a metalinguistic paradigm, however, cannot be aligned with this "preserved-competence" notion. On the contrary, the metalinguistic data strongly suggest that the Broca's grammatical knowledge is limited in the same manner as is his production. This point has been underlined in two of our previous reports (Zurif, Caramazza and Myerson, 1972; Zurif and Caramazza, 1976). The present note has a two-fold purpose: to update these findings, primarily by providing a broader empirical context in which to place them, and to permit us a second pass at their theoretical implications. To briefly describe the paradigm itself, data are gathered by asking patients to judge how words in a written sentence "go best together" in that sentence. No vocal output is required of the patients; in fact, precautions are taken to limit even subvocal factors. The patients need indicate their judgments simply by pointing to the words that they feel cluster best within each of the test sentences (Zurif et al., 1972). These judgment-derived word groupings then serve as input matrices for an algorithmic, hierarchical scaling procedure that generates - for each sentence separately - a graphic description in the form of a phrase structure tree. The more often any two words of a sentence are judged to form a "constituent," the more compact is the node joining these two words. To the extent that these nodes can then be identified in linguistic terms - such as • The research reported here was supported by NINDS Research Grants 11408 and 06209 to Boston University School of Medicine. Cortex (1976) 12, 183-186.
184
E. B. Zurif, E. Green, A. Caramazza and C. Goodenough
verb phrase and the like, we can characterize the grammatical fit of the patients' judgments (Levelt, 1970a, 1970b; Martin, 1970). We first used this paradigm and scaling procedure to test three Broca's aphasics considered to have relatively intact comprehension and three non neurological control patients (Zurif et al., 1972). Both groups were observed to judge affinities among words in a sentence on the basis of an implicit hierarchical organization, but the two groups' subjective hierarchies were noticeably different from each other. The relatedness judgments of the control subjects took into account the surface structure restrictions of the sentences, such as using articles appropriately to mark noun phrases. The aphasic patients, in contrast, coupled the content words together, attending inconsistently to the functors. It must also be emphasized that the aphasics did not just ignore the functors. Rather, they did not seem to know what role they played in a sentences, often either grouping two articles together or, in a completely unprincipled fashion, grouping an article with a main verb. As a result, their judgments violated the linguistic unity of the noun phrases of the sentences (provided by the structure-marking determiners) and also failed to account for copula forms. Stated more generally, the results indicate that a lesion in Broca's area can compromise a patient's tacit knowledge of his language in the same manner as his speech, even when the clinical impression is one of relatively preserved comprehension (see also Goodglass, 1968; Von Stockert, 1972; Gardner, Denes and Zurif, 1975). Yet even granting the above assertion, it does not necessarily follow that agrammatism applies equally to all functors. The terms "functor" or "grammatical morpheme" offer descriptive convenience, but the small words characterized as such do not appear to constitute a single structural or semantic class (Brown, 1973). Consider, in this respect, the two sentences, "The ball was hit to John." vs. "The ball was hit by John." The contrastive use of "to" and "by" entails critical meaning differences between these two sentences; the copula and the definite article, however, are of no consequence either to the contrast in the logical relations, or to the semantic roles of the participants. The obvious point is that functors differ among themselves in the kind of meaning they provide. These differences were not fully explored in the first study. Accordingly, in our second use of the judgment paradigm, we chose sentences in which the functors differed more systematically in their levels and quality of communicative content (Zurif and Caramazza, 1975). Also, in addition to non-neurological control patients and Broca's aphasics with "relatively preserved comprehension," we tested patients whom we termed mixed aphasics. Like the Broca's aphasics, these mixed patients produced labored, non-fluent speech; unlike the Broca's group, they presented clinically moderate comprehension deficits. 2 Again, the judgments yielded consistent differences between normal speakers and aphasics for those clusters involving articles: in each instance the control group linked articles with their respective nouns to form well integrated noun phrases; but both aphasic groups were unsure about the role of the articles, 2 The word "moderate" in this context may be taken to serve only one certain purpose; namely, to define an upper and lower limit to comprehension capacity as assessed clinically and as measured formally by the Boston Diagnostic Aphasia Test (Goodglass and Kaplan, 1972). That is, unlike the Broca's aphasics, none of the mixed group presented what could be termed "relatively intact comprehension;" yet, these patients were sufficiently intact both to be able to read the test sentences and to master the metalinguistic demands of the task. It should also be noted that this clinical picture sometimes arises even when evidence points to a circumscribed anterior lesion (e.g. Hecaen and Consoli, 1973).
Grammatical intuitions of aphasic patients
185
grouping them inconsistently and thus violating the structural unity of the noun phrases. The Broca's aphasics, however, treated very differently those functors which signalled critical underlying structural differences between sentences (i.e., differences involving verb-noun relations). For sentences of the form, "Stories were read to Billy," as well as for the contrasting passives such as, "Stories were read by Billy," the Broca's consistently formed strong links between the final nouns and their associated prepositions.' The normal speakers also grouped the prepositions and the nouns in this fashion; but, significantly, the mixed aphasics failed to show any such pattern. There is, of course, no a priori reason to enthrone these intra-sentences relatedness judgments as the purest measure of the aphasic's language competence. Like laboratory tests of comprehension, of sentences segmentation, and of memory for sentences, or like the data of spontaneous speech, these judgments constitute simply another aspect of performance. Nonetheless, we think it important to emphasize the correspondence between performance on the word-relatedness judgment task and the more usual performance measures of spontaneous speech and comprehension. Mixed aphasics, who have clinically observable comprehension deficits, showed little metalinguistic control of functors, even of functors critical to the syntactic expression of basic semantic relations. In contrast, Broca's aphasics, who clinically present relatively intact comprehension, showed uncertainty only for those functors that are usually of no communicative consequence. Thus, in a general and indirect manner, the meta linguistic patterns parallel those for comprehension, and at the same time are consistent with the telegraphic quality of the routinely observed speech limitations. A study recently completed at the Boston V.A. Hospital by Katherine Kurowski establishes even more directly the parallel between metalinguistic relatedness judgments and comprehension for ongoing speech. Kurowski used sentences identical to those we used. But by adding a sentence-picture matching comprehension test, she was able to show that patients who formed strong links between nouns and prepositions in their relatedness judgments generally had no problem in choosing the correct pictorial representation of these sentences. In cpntrast, patients who failed to form these clusters performed relatively poorly on the test of direct comprehension. It appears, therefore, that the tight links between "to" and "by" and their accompanying nouns are not based simply on a spared memory for some of the more obvious transitional dependencies in various surface forms. Rather, these links signal that Broca's aphasics can process the structural meaning differences entailed in the contrastive use of "to" and "by". The empirical details described to this point lack sufficient scope for us to conclude, however, that Broca's aphasics are intensitive only to fine distinctions involving noun phrases. The sentences we have used- whether passive or active~ have all been rather simple sentences, containing either one sentence node in their underlying structure, or two sentence nodes, but in a right-branching arrangement with each other. Once beyond this initial level of complexity, however- even to forms no more complex than single center-embedded sentences easily understood by six year old children (Caramazza, 1974)- the Broca's aphasic shows a rather dramatic breakdown in comprehension. Specifically, Caramazza has observed that 3 To test that the morpheme "to," in itself, had no undue salience to which the Broca's were sensitive, we included sentences in which "to" served as an infinitival complementizer, the absence of which does not seriously affect the gaining of sentence meaning. Given such sentences, Broca's aphasics grouped "to" on a random basis, thus failing to generate a compact cluster between "to" and the following infinitive.
186
E. B. Zurif, E. Green, A. Caramazza and C. Goodenough
when semantic cues are removed from such forms, by presenting sentences in which both the matrix and the relativized noun phrases are capable of performing the action specified by the verb, the Broca's comprehension is reduced to chance level. Taken together, these findings underline the truism that comprehension is the result of a complex inferential process roughly divided into semantic and syntactic operations. Once Broca's aphasics have processed basic noun-verb relations in simple sentences - presumably in terms of lexical knowledge and what they know about the real world - they are then forced to confront and integrate the syntactic elements that establish these relations. When, however, the syntactic elements appear in complex, semantically unconstrained sentences or when they signal distinctions not directly involving the verb, the Broca's aphasic is incapable of processing them. What seems to emerge from the data, therefore, is that anterior brain damage exerts the same general pattern of disruption to the underlying knowledge of language as it does to speech. The articulatory problems are undoubtedly important determinants of nonfluency in Broca's aphasia, but the concomitant agrammatism is not simply the result of an economizing measure. Rather, it reflects a language limitation.
Acknowledgments. We are indebted to Drs. Howard Gardner, Wolfgang Dressler, Harry Whitaker and Harold Goodglass for their help in developing the notions expressed in this paper. REFERENCES BROWN, R. (1973) A First Language: The Early Stages, Harvard University Press, Cambridge, Mass. CARAMAZZA, A. (1974) Comprehension of sentences of varying complexity in children and aphasic patients, Symposium "The Development and breakdown of language functions: parallels and divergencies," Academy of Aphasia, Warrenton, Va. GARDNER, H., DENES, G., and ZURIF, E.B. (1975) Critical reading at the sentence level in aphasia, "Cortex," 11, 60-72. GoODGLASS, H. (1966) Studies on the grammar of aphasics, in Developments in Applied Psycho linguistics Research, ed. by S. Rosenberg and J. Koplin, MacMillan, New York. and KAPLAN, E. (1972) The Assessment of Aphasia and Related Disorders, Lea and Febiger, Philadelphia, Pa. H:EcAEN, H., and CoNSOLI, S. (1973) Analyse des troubles du langage au cours des tesions de l'aire de Broca, "Neuropsychologia," 11, 377-388. KuROWSKI, K. (Manuscript in preparation) M.A. Thesis, Dept. of Linguistics, Brown University. LENNEBERG, E.H. (1973) The neurology of language, "Daedalus," 102, 115-133. LEVELT, W.].M. (1970a) Introduction - hierarchical clustering algorithms in the psychology of grammar, in Advances in Psycholinguistics, ed. by G.B. Flores d'Arcais and W.J.M. Levelt, North-Holland Publishing Co., Amsterdam. (1970b) A scaling approach to the study of syntactic relations, in Advances in Psycholin guistics, ed. by G.B. Flores d'Arcais and W.J.M. Levelt, North-Holland Publishing Co., Amsterdam. LocKE, S., CAPLAN, D., and KELLAR, L. (1973) A Study in Neurolinguistics, Charles C. Thomas, Springfield, Ill. MARTIN, E. (1970) Toward an analysis of subjective phrase structure, "Psycho!. Bull.," 74, 153-166. VON STOCKERT, T. (1972) Recognition of syntactic structure in aphasia, "Cortex," 8, 323-334. WEIGL, E., and BIERWISCH, M. (1970) Neuropsychology and linguistics: topics of common research, "Foundations of Language," 6. ZuRIF, E.B., and CARAMAZZA, A. (1976) Psycholinguistic structure in aphasia: studies in syntax and semantics, in Studies in Neurolinguistics, ed. by H. Whitaker and H. Whitaker, Academic Press, New York, in press. - , -,and MYERSON, R. (1972) Grammatical judgments of agrammatic aphasics, "Neuropsycholo gia," 10, 405-417. Or. E. B. Zurif, Psychology Service, Boston VA Hospital, 150 South Huntington Ave., Boston, Mass., U.S.A.
GRAMMATICAL INTUITIONS OF APHASIC PATIENTS: SENSITIVITY TO FUNCTORS' E. B. Zurif, E. Green, A. Caramazza and C. Goodenough (Boston University School of Medicine, Boston Veterans Administration Hospital, The John Hopkins University and Universite de Quebec a Montreal)
Routine clinical examinations generally suggest that damage to the frontal area in the left hemisphere - Broca's area - disrupts the ability of patients to produce speech much more than their ability to comprehend. Such patients - Broca's aphasics - often seem to fully understand commands and questions and appear to know what they want to say, yet can only produce short, labored, agrammatic utterances. Like telegrams, these utterances are characterized by the relative omission of bound and unbound grammatical morphemes, or functors, and by a corresponding reliance on content words. This speech pattern and the apparent discrepancy between output and comprehension have been interpreted by some as evidence of preserved language competence in Broca's aphasia (Weigl and Bierwisch, 1970; Lenneberg, 1973; Locke, Caplan and Kellar, 1973). In this view, the patient's tacit knowledge of his language is considered spared, and his agrammatism, simply an economizing measure to circumvent articulatory problems. Evidence that we have recently gained from a metalinguistic paradigm, however, cannot be aligned with this "preserved-competence" notion. On the contrary, the metalinguistic data strongly suggest that the Broca's grammatical knowledge is limited in the same manner as is his production. This point has been underlined in two of our previous reports (Zurif, Caramazza and Myerson, 1972; Zurif and Caramazza, 1976). The present note has a two-fold purpose: to update these findings, primarily by providing a broader empirical context in which to place them, and to permit us a second pass at their theoretical implications. To briefly describe the paradigm itself, data are gathered by asking patients to judge how words in a written sentence "go best together" in that sentence. No vocal output is required of the patients; in fact, precautions are taken to limit even subvocal factors. The patients need indicate their judgments simply by pointing to the words that they feel cluster best within each of the test sentences (Zurif et al., 1972). These judgment-derived word groupings then serve as input matrices for an algorithmic, hierarchical scaling procedure that generates - for each sentence separately - a graphic description in the form of a phrase structure tree. The more often any two words of a sentence are judged to form a "constituent," the more compact is the node joining these two words. To the extent that these nodes can then be identified in linguistic terms - such as • The research reported here was supported by NINDS Research Grants 11408 and 06209 to Boston University School of Medicine. Cortex (1976) 12, 183-186.
184
E. B. Zurif, E. Green, A. Caramazza and C. Goodenough
verb phrase and the like, we can characterize the grammatical fit of the patients' judgments (Levelt, 1970a, 1970b; Martin, 1970). We first used this paradigm and scaling procedure to test three Broca's aphasics considered to have relatively intact comprehension and three non neurological control patients (Zurif et al., 1972). Both groups were observed to judge affinities among words in a sentence on the basis of an implicit hierarchical organization, but the two groups' subjective hierarchies were noticeably different from each other. The relatedness judgments of the control subjects took into account the surface structure restrictions of the sentences, such as using articles appropriately to mark noun phrases. The aphasic patients, in contrast, coupled the content words together, attending inconsistently to the functors. It must also be emphasized that the aphasics did not just ignore the functors. Rather, they did not seem to know what role they played in a sentences, often either grouping two articles together or, in a completely unprincipled fashion, grouping an article with a main verb. As a result, their judgments violated the linguistic unity of the noun phrases of the sentences (provided by the structure-marking determiners) and also failed to account for copula forms. Stated more generally, the results indicate that a lesion in Broca's area can compromise a patient's tacit knowledge of his language in the same manner as his speech, even when the clinical impression is one of relatively preserved comprehension (see also Goodglass, 1968; Von Stockert, 1972; Gardner, Denes and Zurif, 1975). Yet even granting the above assertion, it does not necessarily follow that agrammatism applies equally to all functors. The terms "functor" or "grammatical morpheme" offer descriptive convenience, but the small words characterized as such do not appear to constitute a single structural or semantic class (Brown, 1973). Consider, in this respect, the two sentences, "The ball was hit to John." vs. "The ball was hit by John." The contrastive use of "to" and "by" entails critical meaning differences between these two sentences; the copula and the definite article, however, are of no consequence either to the contrast in the logical relations, or to the semantic roles of the participants. The obvious point is that functors differ among themselves in the kind of meaning they provide. These differences were not fully explored in the first study. Accordingly, in our second use of the judgment paradigm, we chose sentences in which the functors differed more systematically in their levels and quality of communicative content (Zurif and Caramazza, 1975). Also, in addition to non-neurological control patients and Broca's aphasics with "relatively preserved comprehension," we tested patients whom we termed mixed aphasics. Like the Broca's aphasics, these mixed patients produced labored, non-fluent speech; unlike the Broca's group, they presented clinically moderate comprehension deficits. 2 Again, the judgments yielded consistent differences between normal speakers and aphasics for those clusters involving articles: in each instance the control group linked articles with their respective nouns to form well integrated noun phrases; but both aphasic groups were unsure about the role of the articles, 2 The word "moderate" in this context may be taken to serve only one certain purpose; namely, to define an upper and lower limit to comprehension capacity as assessed clinically and as measured formally by the Boston Diagnostic Aphasia Test (Goodglass and Kaplan, 1972). That is, unlike the Broca's aphasics, none of the mixed group presented what could be termed "relatively intact comprehension;" yet, these patients were sufficiently intact both to be able to read the test sentences and to master the metalinguistic demands of the task. It should also be noted that this clinical picture sometimes arises even when evidence points to a circumscribed anterior lesion (e.g. Hecaen and Consoli, 1973).
Grammatical intuitions of aphasic patients
185
grouping them inconsistently and thus violating the structural unity of the noun phrases. The Broca's aphasics, however, treated very differently those functors which signalled critical underlying structural differences between sentences (i.e., differences involving verb-noun relations). For sentences of the form, "Stories were read to Billy," as well as for the contrasting passives such as, "Stories were read by Billy," the Broca's consistently formed strong links between the final nouns and their associated prepositions.' The normal speakers also grouped the prepositions and the nouns in this fashion; but, significantly, the mixed aphasics failed to show any such pattern. There is, of course, no a priori reason to enthrone these intra-sentences relatedness judgments as the purest measure of the aphasic's language competence. Like laboratory tests of comprehension, of sentences segmentation, and of memory for sentences, or like the data of spontaneous speech, these judgments constitute simply another aspect of performance. Nonetheless, we think it important to emphasize the correspondence between performance on the word-relatedness judgment task and the more usual performance measures of spontaneous speech and comprehension. Mixed aphasics, who have clinically observable comprehension deficits, showed little metalinguistic control of functors, even of functors critical to the syntactic expression of basic semantic relations. In contrast, Broca's aphasics, who clinically present relatively intact comprehension, showed uncertainty only for those functors that are usually of no communicative consequence. Thus, in a general and indirect manner, the meta linguistic patterns parallel those for comprehension, and at the same time are consistent with the telegraphic quality of the routinely observed speech limitations. A study recently completed at the Boston V.A. Hospital by Katherine Kurowski establishes even more directly the parallel between metalinguistic relatedness judgments and comprehension for ongoing speech. Kurowski used sentences identical to those we used. But by adding a sentence-picture matching comprehension test, she was able to show that patients who formed strong links between nouns and prepositions in their relatedness judgments generally had no problem in choosing the correct pictorial representation of these sentences. In cpntrast, patients who failed to form these clusters performed relatively poorly on the test of direct comprehension. It appears, therefore, that the tight links between "to" and "by" and their accompanying nouns are not based simply on a spared memory for some of the more obvious transitional dependencies in various surface forms. Rather, these links signal that Broca's aphasics can process the structural meaning differences entailed in the contrastive use of "to" and "by". The empirical details described to this point lack sufficient scope for us to conclude, however, that Broca's aphasics are intensitive only to fine distinctions involving noun phrases. The sentences we have used- whether passive or active~ have all been rather simple sentences, containing either one sentence node in their underlying structure, or two sentence nodes, but in a right-branching arrangement with each other. Once beyond this initial level of complexity, however- even to forms no more complex than single center-embedded sentences easily understood by six year old children (Caramazza, 1974)- the Broca's aphasic shows a rather dramatic breakdown in comprehension. Specifically, Caramazza has observed that 3 To test that the morpheme "to," in itself, had no undue salience to which the Broca's were sensitive, we included sentences in which "to" served as an infinitival complementizer, the absence of which does not seriously affect the gaining of sentence meaning. Given such sentences, Broca's aphasics grouped "to" on a random basis, thus failing to generate a compact cluster between "to" and the following infinitive.
186
E. B. Zurif, E. Green, A. Caramazza and C. Goodenough
when semantic cues are removed from such forms, by presenting sentences in which both the matrix and the relativized noun phrases are capable of performing the action specified by the verb, the Broca's comprehension is reduced to chance level. Taken together, these findings underline the truism that comprehension is the result of a complex inferential process roughly divided into semantic and syntactic operations. Once Broca's aphasics have processed basic noun-verb relations in simple sentences - presumably in terms of lexical knowledge and what they know about the real world - they are then forced to confront and integrate the syntactic elements that establish these relations. When, however, the syntactic elements appear in complex, semantically unconstrained sentences or when they signal distinctions not directly involving the verb, the Broca's aphasic is incapable of processing them. What seems to emerge from the data, therefore, is that anterior brain damage exerts the same general pattern of disruption to the underlying knowledge of language as it does to speech. The articulatory problems are undoubtedly important determinants of nonfluency in Broca's aphasia, but the concomitant agrammatism is not simply the result of an economizing measure. Rather, it reflects a language limitation.
Acknowledgments. We are indebted to Drs. Howard Gardner, Wolfgang Dressler, Harry Whitaker and Harold Goodglass for their help in developing the notions expressed in this paper. REFERENCES BROWN, R. (1973) A First Language: The Early Stages, Harvard University Press, Cambridge, Mass. CARAMAZZA, A. (1974) Comprehension of sentences of varying complexity in children and aphasic patients, Symposium "The Development and breakdown of language functions: parallels and divergencies," Academy of Aphasia, Warrenton, Va. GARDNER, H., DENES, G., and ZURIF, E.B. (1975) Critical reading at the sentence level in aphasia, "Cortex," 11, 60-72. GoODGLASS, H. (1966) Studies on the grammar of aphasics, in Developments in Applied Psycho linguistics Research, ed. by S. Rosenberg and J. Koplin, MacMillan, New York. and KAPLAN, E. (1972) The Assessment of Aphasia and Related Disorders, Lea and Febiger, Philadelphia, Pa. H:EcAEN, H., and CoNSOLI, S. (1973) Analyse des troubles du langage au cours des tesions de l'aire de Broca, "Neuropsychologia," 11, 377-388. KuROWSKI, K. (Manuscript in preparation) M.A. Thesis, Dept. of Linguistics, Brown University. LENNEBERG, E.H. (1973) The neurology of language, "Daedalus," 102, 115-133. LEVELT, W.].M. (1970a) Introduction - hierarchical clustering algorithms in the psychology of grammar, in Advances in Psycholinguistics, ed. by G.B. Flores d'Arcais and W.J.M. Levelt, North-Holland Publishing Co., Amsterdam. (1970b) A scaling approach to the study of syntactic relations, in Advances in Psycholin guistics, ed. by G.B. Flores d'Arcais and W.J.M. Levelt, North-Holland Publishing Co., Amsterdam. LocKE, S., CAPLAN, D., and KELLAR, L. (1973) A Study in Neurolinguistics, Charles C. Thomas, Springfield, Ill. MARTIN, E. (1970) Toward an analysis of subjective phrase structure, "Psycho!. Bull.," 74, 153-166. VON STOCKERT, T. (1972) Recognition of syntactic structure in aphasia, "Cortex," 8, 323-334. WEIGL, E., and BIERWISCH, M. (1970) Neuropsychology and linguistics: topics of common research, "Foundations of Language," 6. ZuRIF, E.B., and CARAMAZZA, A. (1976) Psycholinguistic structure in aphasia: studies in syntax and semantics, in Studies in Neurolinguistics, ed. by H. Whitaker and H. Whitaker, Academic Press, New York, in press. - , -,and MYERSON, R. (1972) Grammatical judgments of agrammatic aphasics, "Neuropsycholo gia," 10, 405-417. Or. E. B. Zurif, Psychology Service, Boston VA Hospital, 150 South Huntington Ave., Boston, Mass., U.S.A.