JOURNAL OF COMMUNICATION DISORDERS 12 ( 1979)) 46 l-479
461
EFFECT OF PRESTIMULATION ON SENTENCE COMPREHENSION BY APHASIC SUBJECTS MARCIE R. WALLER Purdue University, West Lafayette, Indiana 47907
FREDERIC L. DARLEY Speech Pathology. Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901
Aphasic subjects and controls were tested to determine whether comprehension of spoken sentences was enhanced by prestimulation concerning their contents. For each of the 20 test points, the subject listened to the test sentence and selected the corresponding picture from among four pictures presented simultaneously. The preparatory suggestions were given in one test condition and withheld in the other. Each prestimulation consisted of one or two sentences that indicated’the persons, objects, or general situation to be presented in the test sentence. Analysis of variance indicated that the effect of the,prestimulation was not significant.
Introduction
In recent years, the breakdown of language reception has become a focus of following the guidelines of increased research in aphasia. Investigators transformational-generative grammar have examined various syntactic structures for differences in complexity (Parisi and Pizzamiglio, 1970; Levy and Holland, 197 1; Shewan and Canter, 197 1). Other researchers have incorporated linguistic complexity into processing variables, such as rate of utterance and pause time (Gardner et al., 1975; Liles and Brookshire, 1975; Lasky et al., 1976). These investigations similarly indicate that syntactic complexity can be detrimental to comprehension-more so than a simple increase of length-but slower rates and strategically placed pauses (at constituent boundaries) are facilitative. Together, the reports cited here provide important guidelines for the presentation of auditory linguistic stimuli to aphasic patients. However, little research on aphasia has been devoted to the context of the message (Boller et al., 1977). In the recent psycholinguistic literature, investigators have stressed the integrative and inferential processes involved in comprehension while paying less attention to stimuli consisting of isolated sentences and words (Bransford and Franks, 1971; Bransford et al., 1972; Haviland and Clark, 1974; Carpenter and Just, 1977). In fact, it does appear that understanding spoken discourse involves more than just deriving the abstract semantic representation of an individual sentence. Address correspondence 55901.
to: Frederic L. Darley, Speech Pathology,
D Elsevier North Holland,
Inc.,
1979
Mayo Clinic, Rochester,
MN
0021-9924179/O&361-09$01.75
462
M.R. WALLER
and F.L. DARLEY
The importance of context and reference factors in the processing can no longer be denied. As Haviland and Clark (1974) stated:
of sentences
We very rarely process sentences in isolation, and although we can understand such sentences this is not what we normally mean by “understanding” or “comprehension” at all. In ordinary language, these words refer to the way we take in the meaning of a sentence and integrate it with information we already know-from context and from past memory. (p. 5 12) Haviland and Clark (1974) (also Clark and Haviland, 1977; Clark and Clark, 1977) have further discussed the processes in which normal listeners engage during comprehension and have formulated an explanatory mechanism: the Given-New contract. In their strategy, a speaker attempts to relate a new piece of information to his listener. According to cooperative principles of communication, the speaker needs to take into account the knowledge base available to his listener (the Given), which will aid the listener in integrating the new information. For example, a listener hearing the sentence, “It was John who was following Mary, ’ ’ first utilizes syntactic distinctions (here a cleft construction) to separate (that person was John). The Given subsequently serves as an address to where the new item is to be placed or consolidated within the listener’s knowledge system (a system hypothesized by the authors to consist of a series of nodes, each with attached propositional units). If the listener lacks information to match the referents in the sentence, then he must form an indirect antecedent by an inferential bridging process or-if bridging is not possible-establish a new node. According to these authors the integrative role of the Given, or existing information, offers a possible explanation for the seemingly excessive redundancy of language. Haviland and Clark (1974) presented subjects with a series of sentences preceded by direct or indirect antecedents, as indicated below: Target sentence: Direct antecedent: Indirect antecedent:
The beer was warm. We got some beer out of the trunk. We checked the picnic supplies.
(In a second experiment the effect of an indirect antecedent containing the key noun of the target sentence-e.g , beer, in “Andrew was especially fond of beer,” was contrasted with the effect of the direct antecedent.) Subjects were asked to press a button when they “understood” a target sentence. As anticipated, reaction times for sentences provided with direct antecedents were faster, indicating greater ease of comprehension. Data supporting the effect of such manipulations on ease of comprehension can be found in the work of Carpenter and Just (1977). The following definition of comprehension appears to be an accurate reflection of current orientations: “Comprehension, broadly conceived, is an active process that uses prior knowledge to interpret and organize the meanings of utterances ” (Glucksberg and Danks, 1975, p. 114).
PRESTIMULATION
AND SENTENCE
COMPREHENSION
463
The majority of studies concerned with the auditory comprehension of aphasic subjects have utilized brief stimuli-words or sentences-partly because retention span so often is reduced in this population. Frequently the target words or sentences have been unrelated and have been presented with little or no linguistic context. Typically, however, preparatory context and redundancy have increased the speed of normal listeners’ comprehension. With severely impaired aphasic patients, Green and Boller (1974) found that two-word and three-word antecedents (e.g., “Here is something”) facilitated auditory comprehension. Furthermore, aphasic patients have been reported to benefit from increased sentence redundancy (Gardner et al., 1975). Such patients are in particular need of therapeutic strategies and self-cueing devices for dealing with receptive deficits, and it appears that the usefulness of antecedents is worth further exploration. We investigated the effect of auditory prestimulation on aphasic subjects’ performance of a sentence-comprehension task. Of interest was whether prior spoken context would influence the aphasic subjects’ processing of sentences. Method Subjects Sixteen aphasic subjects were selected from among patients referred to the Section of Speech Pathology at the Mayo Clinic (Rochester, MN), the Aphasia Section of the Minneapolis Veterans Administration Hospital, and the Sister Kenny Rehabilitation Institute (Minneapolis, MN). All subjects, as evaluated by the consulting staff in speech pathology, had some deficit in auditory comprehension. The neurologic causes were: left cerebrovascular accident (12); left frontal meningioma or craniotomy (3); and left temporal lobectomy (1). The ages of the aphasic subjects ranged from 22 to 75 and averaged 50 yr. Most of the subjects were hospitalized because of a recent neurologic episode. The time since onset ranged from 15 days to 33 mo (mean: 5.7 mo), but exceeded a year in only three cases. According to medical records, all patients were free of any defects of visual and auditory acuity that would influence performance on the experimental task. The aphasia of each patient had been evaluated extensively by a clinician. No attempt was made to classify the patients on the basis of their oral expression since our interest was in their ability for auditory comprehension. Much current research implies that, between subgroups based on oral expression, the differences in comprehension are only quantitative. (See Parisi and Pizzamiglio, 1970; Shewan and Canter, 1971; Boller et al., 1977.) As a preliminary, all aphasic subjects were given the Token Test (De Renzi and Vignolo, 1962) and subtests VI and X of the Porch Index of Communicative Ability (PICA) (Porch, 1967). The Token Test elicits evidence of the ability of aphasic subjects to deal
464
M.R. WALLER and F.L. DARLEY
with increasing amounts of nonredundant information and to follow syntactic directives in a chip-manipulation task. The PICA subtests require pointing to objects in response to spoken descriptions-words (subtest X) or sentences (subtest VI). From the two PICA subtests, 13 of the aphasic subjects had average scores of 14 to 15 (mean: 14.6) and two others had averages of 13.5. The scores of the 16th patient were not available. Token Test errors on Part V ranged from 3 to 22 (mean: 12.8); no specific cutoff criterion was applied in the selection of subjects. Control subjects consisted of two groups of 16-a younger group of mean age 22 yr and an older one of mean age 55 yr, the latter having been selected for mean age equivalent to that of the aphasic subjects. All control subjects were volunteers from the general maintenance and business staff at the Mayo Clinic. Materials Twenty antecedent-and-sentence pairs were developed for use as experimental stimuli. Each of the 20 target sentences contained a syntactic feature reported to be difficult for aphasic patients (Goodglass et al., 1970; Parisi and Pizzamiglio, 1970; Shewan and Canter, 197 1): before in 3 sentences, after in 3, under in 1, passive in 4, negative passive in 4, indirect object in 2, and direct object in 3. The sentences ranged in length from 8 to 16 words (mean: 11.75). Before hearing the target sentence, subjects received either a spoken antecedent (A) or no antecedent (N). In pilot manipulations, single words had been utilized as the antecedents: but it was decided that the antecedents in the study should be more informative, although that made them longer. The antecedents then became descriptions, one or two sentences long (each antecedent 6 to 17 words in length; mean: 11.75), which indicated persons or objects and something of the general situation to be presented in the target sentence. The following illustrates an antecedent-target sentence pair. Antecedent: Target:
You’ll see some people reading newspapers. Some of them will also be eating. The newspaper was read by the man eating lunch at the counter.
All of the target sentences and their antecedents are presented in the Appendix. Target sentences were tape recorded for presentation at about 130 words per minute, slow rates having been reported as advantageous for auditory comprehension (Lasky et al., 1976). Antecedents were presented in live voice by an experimenter (the same throughout the study) because it was thought that this would provide desirable environmental support. Evidence confirms that aphasic patients do not respond so well to tape-recorded stimuli (Gardner et al., 1975). The subjects’ comprehension was tested by having them select a picture from four possible choices on a ptige. The pictures were black-and-white Clip-Art
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AND SENTENCE
COMPREHENSION
465
drawings, 12.5 cm square. The three foils were closely related to the correct alternative. For example, with the target sentence above (“The newspaper was read by the man eating lunch at the counter”), the following drawings were presented: (1) a man in a business suit sitting at a counter reading a newspaper while eating a sandwich, (2) a woman in a robe drinking a cup of coffee and reading a newspaper; (3) men standing and reading newspapers in a subway car; and (4) a construction worker, with a lunch pail at his feet, sitting on a chair drinking coffee while reading a newspaper. Procedures The subjects participated in two test sessions on consecutive days. All presentations in the same session were of the same type (A or N), and the order of the types was determined randomly. Each subject was presented with a loose-leaf notebook containing 22 pages of pictures. The task was to match the target sentence heard from the tape recorder with one of four pictures on an indicated page. The experimental task was preceded by two examples of a target sentence and picture group. In A presentations, the subject heard the live-voice antecedent, then the tape-recorded signal “show me,” and then the target sentence. The N presentation was simply “show me” and then the target sentence. There was a lo-set pause after each target sentence; but latency was not of concern in the study, and the tape recorder was turned off if the subject had not responded or had requested more time. Repetitions of the target sentence were allowed, but few subjects needed them. In testing of the control subjects, a few modifications were made. Subjects were tested in-groups of four, and all answers were written down on prepared forms. Results Table 1 presents the mean number of correct responses under A and N conditions for younger control subjects, older control subjects, and aphasic subjects. Analysis of variance indicated that the effects of the antecedents were not significant in any of the three subject groups. The younger and older control subjects, as expected, usually failed on only one or two trials (average correct: 94%), regardless of condition. Comparison (by inspection) of A means versus N means, subject by subject, revealed trends for slight facilitation by use of antecedents. The younger group of subjects performed the same in the two testing sessions, but the older group improved significantly on their second exposure (F = 6.48; df = 1, 14;~ < 0.025). Among the aphasic subjects the mean of correct responses was 76%. Sentences of negative passive form were especially difficult for these subjects,
466
M.R. WALLER and F.L. DARLEY
Correct Responses
TABLE 1 by Younger and Older Control Subjects and Aphasic Patients, (A) and No Antecedent (N) Conditions Controls Test
Aphasic patients
Older
Younger
With Antecedent
Condition
day
Mean
SD
Mean
SD
Mean
SD
N
1 2 1 2
18.6 19.0 19.4 19.1
1.4 0.8 1.1 1.1
17.9 18.9 18.9 18.6
1 .o 0.6 1.1 1.5
15.0 15.1 14.8 16.4
1.9
A A
N
1.8
3.2 2.4
substantiating reports from other investigations. Inspection of single-subject data confirmed the similarity of response under A and N conditions: the A and N scores of individual aphasic subjects were even closer than those of the individual control subjects. Nevertheless, one aphasic subject did lose 5 points from the A test on day 1 to the N test on day 2; and this decrease contributed to a marginally significant order effect in the data of the aphasic subjects (F = 4.20; df = 1, 14;~ = 0.057). It is of interest that the antecedents did not appear to overload the subjects-that is, negatively influence accuracy levels. Discussion The effect of antecedent information is questionable. However, prestimulation may have potentialities not allowed by the design of this study. Therapeutically, clinicians attempt to engage a patient’s linguistic mechanisms maximally, not simply to initiate rote types of responding and processing. In regard to tasks of naming, for instance, Brookshire (1975) reported that having patients repeat prompted vocabulary items did not improve their ability to deal with items not drilled on: more active participation appears to be a stimulus for meaningful processing. Earlier reports indicated that ease and depth of comprehension by normal subjects were facilitated by prior information. Our study was concerned only with the accuracy of responses, not with latency or extent of retention. Perhaps prestimulation has a strategic value, not evident in plus-minus scoring, for increasing the depth of comprehension. According to Glucksberg and Danks (1973, comprehension of a sentence involves the following operations: assigning meaning to words, analyzing syntactic and semantic relations, and integrating the information as quickly as possible to reduce the load on immediate memory. Possibly the speed of integration may be increased by some kind of contextual support, especially in a patient population whose retention may be deficient. A factor of utmost importance to our results is the difficulties of aphasic
PRESTIMULATION
AND SENTENCE COMPREHENSION
467
patients with syntactic analysis. In our study, the aphasic subjects’ difficulty with the syntax of the sentences may have limited the benefit from antecedents. Earlier in the development of the research, we considered the hypothesis that antecedent knowledge might allow aphasic subjects to focus on the more abstract task of deciphering the syntactic relations within a sentence, but it appears that completion of syntactic analysis may be prerequisite to the possible contextual benefits. It should be mentioned that the syntax of the 20 target sentences is complicated, a factor that made it more difficult for the subjects to separate Given and New information. Further, although the antecedents provided basic referential information (e.g., as in “the man, ” provided referents for the nouns in the target sentences), they necessarily were of a somewhat general nature, so as not to aid the subjects in eliminating the pictorial alternatives. The direct antecedents in Haviland and Clark’s (1974) study of reaction time corresponded more specifically to the new assertion in each target sentence, and the favorable results obtained might warrant employment of direct antecedents in future research. Certainly, redundancy and contextual prestimulation need to be investigated further with aphasic patients. Appendix Spoken Antecedents 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
11. 12. 13.
(A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T):
(A) and Target Sentences (T)
You’ll see some people reading newspapers. Some of them will also be eating. The newspaper was read by the man eating lunch at the counter. You’ll see some workers in a factory. It’s late in the day. The workers all checked the bulletin board before they leftfor the day. You’ll see some people studying and doing schoolwork here. The boy shows the girl how to write the answer. You’ll see a trial going on. The judge is sympathetic to the young man on trial. The judge talked to the defendant before the lawyerspresented their case. You’ll see a baby and his parents. Many times the father helps out and feeds the baby. Today the baby was notfed by his father. You’ll see some men working on cars. It has been a busy day today. A man was still working under the car. You’ll see a man who’s finished work. Each night he buys a newspaper on the way home. After taking the train home, the man sat reading the newspaper. You’ll see some men and some police. Crime is rising in the city. This man has not been caught by the police. You’ll see a trial going on. The judge has decided on the sentence. The young boy listened to the sentence reached by the judge. You’ll see a doctor and he’s discussing a woman’s x-rays. The doctor explains the woman’s x-rays to his nurse. You’ll see a protest march. The police expect it to be nonviolent. The protest was not stopped by the police in the area. You’ll see a newborn baby. His father is seeing him for the first time. The baby was put in the incubator after thefather said goodbye to him. You’ll see a doctor. He’s explaining some x-rays. The doctor showed the man his wife’s r-rays.
468
14. 15. 16. 17. 18. 19. 20.
M.R. WALLER and F.L. DARLEY
(A); (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T):
You’ll see some men reading newspapers. The newspaper was not read by the man indoors. You’ll see some men at work. A new salesman has just joined the staff. The man introduced the new salesman to the district manager. You’ll see some men and boys talking in different situations. The man shows the boy the answer to the problem. You’ll see some police at work. They regularly patrol certain areas. He had better hurry before the police arrive on the scene. You’ll see a man with a newspaper The newspaper is read by the man standing on the train. You’ll see some family pictures. It’s a beautiful day to be outside. The parents took the babyfor a walk in his buggy after hefinished his bottle. You’ll see some pictures of families together. The little girl was picked up by herfather.
References Boiler, F., Kim, Y., Mack, J. L. (1977). Auditory comprehension in aphasia. In H. Whitaker, H. A. Whitaker (eds.), Studies in Neurolinguistics. Vol. 3. New York: Academic Press. Bransford, J. D., Barclay, J. R., Franks, J. J. (1972). Sentence memory: a constructive versus interpretive approach. Cognitive Psycho/. 3: 193-209. Bransford, J. D., Franks, J. J. (1971). The abstraction of linguistic ideas. Cognitive Psychol. 2: 331-350. Brookshire, R. H. (1975) Effects of prompting on spontaneous naming of pictures by aphasic subjects. Hum. Commun. 3: 63-71. Carpenter, P. A., Just, M. A. (1977). Integrative processes in comprehension. In D. LaBerge, S. J. Samuels (eds.), Basic Processes in Reading: Perception and Comprehension. Hillsdale, NJ: Lawrence Erlbaum Associates. Clark, H. H., Clark, E. V. (1977). Psychology and Language: An Introduction to Psycholinguistics. New York: Harcourt, Brace, Jovanovich. Clark, H. H., Haviland, S. E. (1977). Comprehension and the given-new contract, In R. 0. Freedle (ed.), Discourse Production and Comprehension. Norwood, NJ: Ablex Publishing. De Renzi, E., Vignolo, L. A. (1962). The token test: a sensitive test to detect receptive disturbances in aphasics. Brain 85: 66S678. Gardner, H., Albert, M. L., Weintraub, S. (1975). Comprehending a word: the influence of speed and redundancy on auditory comprehension in aphasia. Cortex 11: 15.%162. Glucksberg, S., Danks, J. H. (1975). Experimental Psycholinguistics: An Introduction. Hillsdale, NJ: Lawrence Erlbaum Associates. Goodglass, H., Gleason, J. B., Hyde, M. R. (1970). Some dimensions of auditory language comprehension in aphasia. .I. Sp. Hear. Res. 13: 595-606. Green, E., Boller, F. (1974). Features of auditory comprehension in severely impaired aphasics. Cortex 10: 133-145. Haviland, S. E., Ciark, H. H. (1974). What’s new: Acquiring new information as a process in comprehension. J. Verb. Learn. Verb. Behav. 13: 512-521. Lasky, E. Z., Weidner, W. E., Johnson, J. P. (1976). Influence of linguistic complexity, rate of presentation, and interphrase pause time on auditory-verbal comprehension of adult aphasic patients. Brain Lang. 3: 386395. Levy, C. E., Holland, A. L. (1971). Influence of grammatical complexity and sentence length on comprehension with adult aphasics. In A. Holland (ed.), Psycholinguistics and behavioral variables underlying recovery from aphasia. Project report submitted to Social and Rehabilitative Service, Dept. of Health, Education, and Welfare, No. RD-3116~SW-69.
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Liles, B. Z., Brookshire, R. H. (1975). The effects of pause time on auditory comprehension of aphasic subjects. J. Commun. Dis. 8: 221-235. Parisi, D., Pizzamiglio, L. (1970). Syntactic comprehension in aphasia. Correx 6: 204-215. Porch, B. E. (1967). Porch Index of Communicarive Ability. Palo Alto, CA: Consulting Psychologists Press. Shewan, C. M., Canter, C. J. (1971). Effects of vocabulary, syntax, and sentence length on auditory comprehension in aphasic patients. Cortex 7: 209226.
461
EFFECT OF PRESTIMULATION ON SENTENCE COMPREHENSION BY APHASIC SUBJECTS MARCIE R. WALLER Purdue University, West Lafayette, Indiana 47907
FREDERIC L. DARLEY Speech Pathology. Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55901
Aphasic subjects and controls were tested to determine whether comprehension of spoken sentences was enhanced by prestimulation concerning their contents. For each of the 20 test points, the subject listened to the test sentence and selected the corresponding picture from among four pictures presented simultaneously. The preparatory suggestions were given in one test condition and withheld in the other. Each prestimulation consisted of one or two sentences that indicated’the persons, objects, or general situation to be presented in the test sentence. Analysis of variance indicated that the effect of the,prestimulation was not significant.
Introduction
In recent years, the breakdown of language reception has become a focus of following the guidelines of increased research in aphasia. Investigators transformational-generative grammar have examined various syntactic structures for differences in complexity (Parisi and Pizzamiglio, 1970; Levy and Holland, 197 1; Shewan and Canter, 197 1). Other researchers have incorporated linguistic complexity into processing variables, such as rate of utterance and pause time (Gardner et al., 1975; Liles and Brookshire, 1975; Lasky et al., 1976). These investigations similarly indicate that syntactic complexity can be detrimental to comprehension-more so than a simple increase of length-but slower rates and strategically placed pauses (at constituent boundaries) are facilitative. Together, the reports cited here provide important guidelines for the presentation of auditory linguistic stimuli to aphasic patients. However, little research on aphasia has been devoted to the context of the message (Boller et al., 1977). In the recent psycholinguistic literature, investigators have stressed the integrative and inferential processes involved in comprehension while paying less attention to stimuli consisting of isolated sentences and words (Bransford and Franks, 1971; Bransford et al., 1972; Haviland and Clark, 1974; Carpenter and Just, 1977). In fact, it does appear that understanding spoken discourse involves more than just deriving the abstract semantic representation of an individual sentence. Address correspondence 55901.
to: Frederic L. Darley, Speech Pathology,
D Elsevier North Holland,
Inc.,
1979
Mayo Clinic, Rochester,
MN
0021-9924179/O&361-09$01.75
462
M.R. WALLER
and F.L. DARLEY
The importance of context and reference factors in the processing can no longer be denied. As Haviland and Clark (1974) stated:
of sentences
We very rarely process sentences in isolation, and although we can understand such sentences this is not what we normally mean by “understanding” or “comprehension” at all. In ordinary language, these words refer to the way we take in the meaning of a sentence and integrate it with information we already know-from context and from past memory. (p. 5 12) Haviland and Clark (1974) (also Clark and Haviland, 1977; Clark and Clark, 1977) have further discussed the processes in which normal listeners engage during comprehension and have formulated an explanatory mechanism: the Given-New contract. In their strategy, a speaker attempts to relate a new piece of information to his listener. According to cooperative principles of communication, the speaker needs to take into account the knowledge base available to his listener (the Given), which will aid the listener in integrating the new information. For example, a listener hearing the sentence, “It was John who was following Mary, ’ ’ first utilizes syntactic distinctions (here a cleft construction) to separate (that person was John). The Given subsequently serves as an address to where the new item is to be placed or consolidated within the listener’s knowledge system (a system hypothesized by the authors to consist of a series of nodes, each with attached propositional units). If the listener lacks information to match the referents in the sentence, then he must form an indirect antecedent by an inferential bridging process or-if bridging is not possible-establish a new node. According to these authors the integrative role of the Given, or existing information, offers a possible explanation for the seemingly excessive redundancy of language. Haviland and Clark (1974) presented subjects with a series of sentences preceded by direct or indirect antecedents, as indicated below: Target sentence: Direct antecedent: Indirect antecedent:
The beer was warm. We got some beer out of the trunk. We checked the picnic supplies.
(In a second experiment the effect of an indirect antecedent containing the key noun of the target sentence-e.g , beer, in “Andrew was especially fond of beer,” was contrasted with the effect of the direct antecedent.) Subjects were asked to press a button when they “understood” a target sentence. As anticipated, reaction times for sentences provided with direct antecedents were faster, indicating greater ease of comprehension. Data supporting the effect of such manipulations on ease of comprehension can be found in the work of Carpenter and Just (1977). The following definition of comprehension appears to be an accurate reflection of current orientations: “Comprehension, broadly conceived, is an active process that uses prior knowledge to interpret and organize the meanings of utterances ” (Glucksberg and Danks, 1975, p. 114).
PRESTIMULATION
AND SENTENCE
COMPREHENSION
463
The majority of studies concerned with the auditory comprehension of aphasic subjects have utilized brief stimuli-words or sentences-partly because retention span so often is reduced in this population. Frequently the target words or sentences have been unrelated and have been presented with little or no linguistic context. Typically, however, preparatory context and redundancy have increased the speed of normal listeners’ comprehension. With severely impaired aphasic patients, Green and Boller (1974) found that two-word and three-word antecedents (e.g., “Here is something”) facilitated auditory comprehension. Furthermore, aphasic patients have been reported to benefit from increased sentence redundancy (Gardner et al., 1975). Such patients are in particular need of therapeutic strategies and self-cueing devices for dealing with receptive deficits, and it appears that the usefulness of antecedents is worth further exploration. We investigated the effect of auditory prestimulation on aphasic subjects’ performance of a sentence-comprehension task. Of interest was whether prior spoken context would influence the aphasic subjects’ processing of sentences. Method Subjects Sixteen aphasic subjects were selected from among patients referred to the Section of Speech Pathology at the Mayo Clinic (Rochester, MN), the Aphasia Section of the Minneapolis Veterans Administration Hospital, and the Sister Kenny Rehabilitation Institute (Minneapolis, MN). All subjects, as evaluated by the consulting staff in speech pathology, had some deficit in auditory comprehension. The neurologic causes were: left cerebrovascular accident (12); left frontal meningioma or craniotomy (3); and left temporal lobectomy (1). The ages of the aphasic subjects ranged from 22 to 75 and averaged 50 yr. Most of the subjects were hospitalized because of a recent neurologic episode. The time since onset ranged from 15 days to 33 mo (mean: 5.7 mo), but exceeded a year in only three cases. According to medical records, all patients were free of any defects of visual and auditory acuity that would influence performance on the experimental task. The aphasia of each patient had been evaluated extensively by a clinician. No attempt was made to classify the patients on the basis of their oral expression since our interest was in their ability for auditory comprehension. Much current research implies that, between subgroups based on oral expression, the differences in comprehension are only quantitative. (See Parisi and Pizzamiglio, 1970; Shewan and Canter, 1971; Boller et al., 1977.) As a preliminary, all aphasic subjects were given the Token Test (De Renzi and Vignolo, 1962) and subtests VI and X of the Porch Index of Communicative Ability (PICA) (Porch, 1967). The Token Test elicits evidence of the ability of aphasic subjects to deal
464
M.R. WALLER and F.L. DARLEY
with increasing amounts of nonredundant information and to follow syntactic directives in a chip-manipulation task. The PICA subtests require pointing to objects in response to spoken descriptions-words (subtest X) or sentences (subtest VI). From the two PICA subtests, 13 of the aphasic subjects had average scores of 14 to 15 (mean: 14.6) and two others had averages of 13.5. The scores of the 16th patient were not available. Token Test errors on Part V ranged from 3 to 22 (mean: 12.8); no specific cutoff criterion was applied in the selection of subjects. Control subjects consisted of two groups of 16-a younger group of mean age 22 yr and an older one of mean age 55 yr, the latter having been selected for mean age equivalent to that of the aphasic subjects. All control subjects were volunteers from the general maintenance and business staff at the Mayo Clinic. Materials Twenty antecedent-and-sentence pairs were developed for use as experimental stimuli. Each of the 20 target sentences contained a syntactic feature reported to be difficult for aphasic patients (Goodglass et al., 1970; Parisi and Pizzamiglio, 1970; Shewan and Canter, 197 1): before in 3 sentences, after in 3, under in 1, passive in 4, negative passive in 4, indirect object in 2, and direct object in 3. The sentences ranged in length from 8 to 16 words (mean: 11.75). Before hearing the target sentence, subjects received either a spoken antecedent (A) or no antecedent (N). In pilot manipulations, single words had been utilized as the antecedents: but it was decided that the antecedents in the study should be more informative, although that made them longer. The antecedents then became descriptions, one or two sentences long (each antecedent 6 to 17 words in length; mean: 11.75), which indicated persons or objects and something of the general situation to be presented in the target sentence. The following illustrates an antecedent-target sentence pair. Antecedent: Target:
You’ll see some people reading newspapers. Some of them will also be eating. The newspaper was read by the man eating lunch at the counter.
All of the target sentences and their antecedents are presented in the Appendix. Target sentences were tape recorded for presentation at about 130 words per minute, slow rates having been reported as advantageous for auditory comprehension (Lasky et al., 1976). Antecedents were presented in live voice by an experimenter (the same throughout the study) because it was thought that this would provide desirable environmental support. Evidence confirms that aphasic patients do not respond so well to tape-recorded stimuli (Gardner et al., 1975). The subjects’ comprehension was tested by having them select a picture from four possible choices on a ptige. The pictures were black-and-white Clip-Art
PRESTIMIJLATION
AND SENTENCE
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drawings, 12.5 cm square. The three foils were closely related to the correct alternative. For example, with the target sentence above (“The newspaper was read by the man eating lunch at the counter”), the following drawings were presented: (1) a man in a business suit sitting at a counter reading a newspaper while eating a sandwich, (2) a woman in a robe drinking a cup of coffee and reading a newspaper; (3) men standing and reading newspapers in a subway car; and (4) a construction worker, with a lunch pail at his feet, sitting on a chair drinking coffee while reading a newspaper. Procedures The subjects participated in two test sessions on consecutive days. All presentations in the same session were of the same type (A or N), and the order of the types was determined randomly. Each subject was presented with a loose-leaf notebook containing 22 pages of pictures. The task was to match the target sentence heard from the tape recorder with one of four pictures on an indicated page. The experimental task was preceded by two examples of a target sentence and picture group. In A presentations, the subject heard the live-voice antecedent, then the tape-recorded signal “show me,” and then the target sentence. The N presentation was simply “show me” and then the target sentence. There was a lo-set pause after each target sentence; but latency was not of concern in the study, and the tape recorder was turned off if the subject had not responded or had requested more time. Repetitions of the target sentence were allowed, but few subjects needed them. In testing of the control subjects, a few modifications were made. Subjects were tested in-groups of four, and all answers were written down on prepared forms. Results Table 1 presents the mean number of correct responses under A and N conditions for younger control subjects, older control subjects, and aphasic subjects. Analysis of variance indicated that the effects of the antecedents were not significant in any of the three subject groups. The younger and older control subjects, as expected, usually failed on only one or two trials (average correct: 94%), regardless of condition. Comparison (by inspection) of A means versus N means, subject by subject, revealed trends for slight facilitation by use of antecedents. The younger group of subjects performed the same in the two testing sessions, but the older group improved significantly on their second exposure (F = 6.48; df = 1, 14;~ < 0.025). Among the aphasic subjects the mean of correct responses was 76%. Sentences of negative passive form were especially difficult for these subjects,
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Correct Responses
TABLE 1 by Younger and Older Control Subjects and Aphasic Patients, (A) and No Antecedent (N) Conditions Controls Test
Aphasic patients
Older
Younger
With Antecedent
Condition
day
Mean
SD
Mean
SD
Mean
SD
N
1 2 1 2
18.6 19.0 19.4 19.1
1.4 0.8 1.1 1.1
17.9 18.9 18.9 18.6
1 .o 0.6 1.1 1.5
15.0 15.1 14.8 16.4
1.9
A A
N
1.8
3.2 2.4
substantiating reports from other investigations. Inspection of single-subject data confirmed the similarity of response under A and N conditions: the A and N scores of individual aphasic subjects were even closer than those of the individual control subjects. Nevertheless, one aphasic subject did lose 5 points from the A test on day 1 to the N test on day 2; and this decrease contributed to a marginally significant order effect in the data of the aphasic subjects (F = 4.20; df = 1, 14;~ = 0.057). It is of interest that the antecedents did not appear to overload the subjects-that is, negatively influence accuracy levels. Discussion The effect of antecedent information is questionable. However, prestimulation may have potentialities not allowed by the design of this study. Therapeutically, clinicians attempt to engage a patient’s linguistic mechanisms maximally, not simply to initiate rote types of responding and processing. In regard to tasks of naming, for instance, Brookshire (1975) reported that having patients repeat prompted vocabulary items did not improve their ability to deal with items not drilled on: more active participation appears to be a stimulus for meaningful processing. Earlier reports indicated that ease and depth of comprehension by normal subjects were facilitated by prior information. Our study was concerned only with the accuracy of responses, not with latency or extent of retention. Perhaps prestimulation has a strategic value, not evident in plus-minus scoring, for increasing the depth of comprehension. According to Glucksberg and Danks (1973, comprehension of a sentence involves the following operations: assigning meaning to words, analyzing syntactic and semantic relations, and integrating the information as quickly as possible to reduce the load on immediate memory. Possibly the speed of integration may be increased by some kind of contextual support, especially in a patient population whose retention may be deficient. A factor of utmost importance to our results is the difficulties of aphasic
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patients with syntactic analysis. In our study, the aphasic subjects’ difficulty with the syntax of the sentences may have limited the benefit from antecedents. Earlier in the development of the research, we considered the hypothesis that antecedent knowledge might allow aphasic subjects to focus on the more abstract task of deciphering the syntactic relations within a sentence, but it appears that completion of syntactic analysis may be prerequisite to the possible contextual benefits. It should be mentioned that the syntax of the 20 target sentences is complicated, a factor that made it more difficult for the subjects to separate Given and New information. Further, although the antecedents provided basic referential information (e.g., as in “the man, ” provided referents for the nouns in the target sentences), they necessarily were of a somewhat general nature, so as not to aid the subjects in eliminating the pictorial alternatives. The direct antecedents in Haviland and Clark’s (1974) study of reaction time corresponded more specifically to the new assertion in each target sentence, and the favorable results obtained might warrant employment of direct antecedents in future research. Certainly, redundancy and contextual prestimulation need to be investigated further with aphasic patients. Appendix Spoken Antecedents 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
11. 12. 13.
(A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T):
(A) and Target Sentences (T)
You’ll see some people reading newspapers. Some of them will also be eating. The newspaper was read by the man eating lunch at the counter. You’ll see some workers in a factory. It’s late in the day. The workers all checked the bulletin board before they leftfor the day. You’ll see some people studying and doing schoolwork here. The boy shows the girl how to write the answer. You’ll see a trial going on. The judge is sympathetic to the young man on trial. The judge talked to the defendant before the lawyerspresented their case. You’ll see a baby and his parents. Many times the father helps out and feeds the baby. Today the baby was notfed by his father. You’ll see some men working on cars. It has been a busy day today. A man was still working under the car. You’ll see a man who’s finished work. Each night he buys a newspaper on the way home. After taking the train home, the man sat reading the newspaper. You’ll see some men and some police. Crime is rising in the city. This man has not been caught by the police. You’ll see a trial going on. The judge has decided on the sentence. The young boy listened to the sentence reached by the judge. You’ll see a doctor and he’s discussing a woman’s x-rays. The doctor explains the woman’s x-rays to his nurse. You’ll see a protest march. The police expect it to be nonviolent. The protest was not stopped by the police in the area. You’ll see a newborn baby. His father is seeing him for the first time. The baby was put in the incubator after thefather said goodbye to him. You’ll see a doctor. He’s explaining some x-rays. The doctor showed the man his wife’s r-rays.
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14. 15. 16. 17. 18. 19. 20.
M.R. WALLER and F.L. DARLEY
(A); (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T): (A): (T):
You’ll see some men reading newspapers. The newspaper was not read by the man indoors. You’ll see some men at work. A new salesman has just joined the staff. The man introduced the new salesman to the district manager. You’ll see some men and boys talking in different situations. The man shows the boy the answer to the problem. You’ll see some police at work. They regularly patrol certain areas. He had better hurry before the police arrive on the scene. You’ll see a man with a newspaper The newspaper is read by the man standing on the train. You’ll see some family pictures. It’s a beautiful day to be outside. The parents took the babyfor a walk in his buggy after hefinished his bottle. You’ll see some pictures of families together. The little girl was picked up by herfather.
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Liles, B. Z., Brookshire, R. H. (1975). The effects of pause time on auditory comprehension of aphasic subjects. J. Commun. Dis. 8: 221-235. Parisi, D., Pizzamiglio, L. (1970). Syntactic comprehension in aphasia. Correx 6: 204-215. Porch, B. E. (1967). Porch Index of Communicarive Ability. Palo Alto, CA: Consulting Psychologists Press. Shewan, C. M., Canter, C. J. (1971). Effects of vocabulary, syntax, and sentence length on auditory comprehension in aphasic patients. Cortex 7: 209226.
