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Preservation of orthographic knowledge in aphasia
BRAIN
AND
LANGUAGE
14, 307-314 (1981)
Preservation of Orthographic Knowledge in Aphasia RHONDA B. FRIEDMAN Boston
University
School
of Medicine, Medical
and Aphasia Center
Research
Center,
Boston
V.A.
A simple untimed lexical decision task was designed to test implicit letter recognition in aphasic patients. Half of the nonwords used in this task were orthographically regular pronounceable pseudowords, and half were orthographically irregular unpronounceable letter strings. Twenty-five randomly chosen aphasic patients with mild to severe degrees of aphasia participated in the study. Although only six of the patients performed the lexical decision task successfully, all 25 demonstrated the ability to distinguish orthographically regular from irregular letter strings and, by implication, the ability to recognize and make use of the identities of written letters.
Aphasia following damage to the left hemisphere of the brain is usually accompanied by some degree of reading disturbance (Goodglass & Geschwind, 1969). The alexias are often subdivided into two categories, “literal alexia” in which words are read better than letters, and “verbal alexia” in which letters are read better than words (Benson, 1976). Global alexia refers to the total inability to read either words or letters (Albert, 1979). The existence of literal alexia in the absence of verbal alexia may at first seem puzzling. Since it is a particular sequence of letters which uniquely determines a word, it follows that the letters of a word must be identified if the word is to be identified. Closer examination of the phenomenon of literal alexia helps to resolve the apparent contradiction. Although literal alexia is often defined as the inability to “read” or “identify” letters (Benson, Brown, & Tomlinson, 1971), these terms are misleading. What is really deficient in patients said to have literal alexia is the ability to name letters, i.e., the ability to look at a b and call it This work was supported by USPHS Fellowship NS06065 and by USPHS Grant NS06209. I would like to thank Roger Graves, Edgar Zurif, Harold Goodglass, and Marjorie Perlman for their helpful comments. Please address reprint requests to: Dr. Rhonda B. Friedman, Psychology Service (116B), Veterans Administration Medical Center, 150 S. Huntington Avenue, Boston, MA 02130. 307 0093-934X/060307-08$02.00/0 Copyright 0 1981 by Academic Press, Inc. All rights of reproduction in any form reserved.
308
RHONDA
B. FRIEDMAN
a “b.” But it is letter recognition, not letter naming, which is the prerequisite to word identification. Letter recognition, as opposed to letter naming, may be tested by having the patient match upper case letters to lower case letters or print letters to script letters (Benson & Geschwind, 1969); such a test is included in the Boston Diagnostic Aphasia Examination (Goodglass & Kaplan, 1972). This task is a good test of the patient’s ability to recognize isolated letters as familiar symbols. Nevertheless, failure on this task need not indicate an inability to recognize letter identities in other situations. We know that such dissociations exist within other domains of aphasia. For example, a patient who does not respond appropriately to the words eyes or hair within the context of a pointing task may nevertheless respond appropriately to the commands “Close your eyes” and “Comb ‘your hair.” Similarly, it is possible that a patient who fails to demonstrate any recognition of single letters in isolation may nevertheless be able to make decisions based upon letter identity when the letters occur within the context of a letter string. The following experiment tests the degree to which implicit letter recognition-i.e., the ability to use letter identities in making other judgments about letter strings-is retained in the aphasic patient. The task will be one of distinguishing real words from letter strings which do not comprise real words. No explicit letter naming or letter matching is required, nor does the patient have to identify any of the words in the list. The patient’s sole task is to indicate recognition of familiar letter strings (i.e., words). Since words can be distinguished from nonwords only on the basis of the letters of which they are composed, success on this task necessarily implies that successful letter recognition has occurred as well. An additional factor which was built into the study is concerned with the orthographic structure of the nonwords. Much recent research has shown that the adult reader is sensitive not only to the actual “wordness” of a string, but also to its orthographic regularity (Baron & Thurston, 1973; Miller, Bruner, & Postman, 1954) and pronounceability (Gibson, Pick, Osser, & Hammond, 1962). In fact, some authors (Baron & Thurston, 1973; Massaro, 1975) suggest that readers may be more sensitive to orthographic regularity than to familiarity (wordness). Since orthographic regularity may affect performance in some way, half of all nonwords in this task were orthographically regular, and half were not. METHODS Design A stack of 40 cards was placed in front of the patient, each card containing one fourletter string. One-half of the strings were real words; one-fourth were orthographically regular pronounceable nonwords, called “pseudowords” (e.g., felp); and one-fourth were
ORTHOGRAPHIC
KNOWLEDGE
IN APHASIA
309
orthographically irregular, unpronounceable letter strings (e.g., bdxc). The subject was instructed to place all the words in one pile, all the nonwords in a separate pile. This was demonstrated explicitly to the patient with a set of 9 practice items. For patients with comprehension difficulties, a dictionary was employed to aid in explaining the task. The dictionary was shown to the patient and he was asked if he recognized it. All patients readily acknowledged that they knew what the dictionary was. The patient was told to put all those items which were contained within the dictionary on top of the dictionary and all others in a separate place. This was demonstrated with the practice items. Some patients, who for some reason found it difficult or uncomfortable to lift each card and place it into one of the piles, simply pointed to one pile or the other as the examiner held up each card.
Subjects The subjects were 25 aphasic patients on the Aphasia/Neurobehavioral Service of the Boston Veterans Administration Medical Center. There were no special criteria for participation in the study; only those aphasic patients with poor eyesight, evidence of childhood reading difficulties, or an expressed dislike of testing were not asked to participate. The patients spanned a wide range of auditory comprehension and reading abilities. They fell into the following categories of aphasia type, based on clinical evaluations and scores on the Boston Diagnostic Aphasia Examination (Goodglass & Kaplan, 1972): nine global, five Wernicke’s, three Broca’s, three “other” nonfluent aphasias,’ two conduction, two anemic, and one transcortical sensory aphasia.
RESULTS
The number of correct responses for each type of letter string (word, pseudoword, unrelated letter string) was recorded for each patient. A patient was considered to have correctly categorized a letter string type if he placed a significant proportion of the items in the correct pile. The .05 significance levels were determined by binominal test to be the following: 9/10 correct for pseudowords (PW’s) and unrelated letters (UL’s); 15/20 correct for words. Five patterns of results emerged. They are shown in Table 1. The five groups may be characterized as follows: Group 1. The three patients in this group correctly classified the UL’s as nonwords and the words as words, but consistently classified the PW’s incorrectly as words (i.e., placed at least 9 of 10 PW’s into the word pile). Group 2. These four patients performed randomly on words and PW’s, putting some words and some PW’s in each pile, while correctly classifying all UL’s as nonwords. Group 3. Eleven patients correctly classified all UL’s and all words, but performed randomly with PW’s, classifying some as words, some as nonwords. ’ These three patients presented with nonfluent speech typical of Broca’s aphasia. However, Patients 18 and 24 displayed comprehension deficits which were far more severe than the typical Broca’s aphasia patient, while Patient 23 displayed a disproportionately severe anarthria.
310
RHONDA
B. FRIEDMAN
TABLE
1
THE FIVE PATTERNS OF RESULTS
Group
Words
Pseudowords
I
Correct
2 3 4 5
Random Correct Correct Random
Consistently incorrect Random Random Correct Correct
Unrelated letters Correct Correct Correct Correct Correct
Group 4. The six patients in this group correctly classified all three types of letter strings; that is, they put the real words in one pile, and the PW’s and UL’s in another. Group 5. One patient placed all the UL’s and PW’s in the nonword pile, yet failed to consistently place all words in the correct pile. The different error patterns are suggestive of different degrees of impairment in the ability to recognize two separate types of properties of letter strings-familiarity (have I seen this letter string before?) and orthographic regularity (does this letter string conform to the orthographic rules of the language?). The task required the patient to classify solely on the basis of familiarity; the patient was never specifically asked to attend to orthographic regularity. Yet when the task was failed, incorrect responses appeared to reflect decisions based upon orthographic regularity rather than pure guessing. The five groups of error patterns are discussed below with regard to the factors of familiarity and orthographic regularity. Group 2. The consistent but incorrect placement of PW’s into the word pile by these patients indicates a breakdown in the ability to distinguish familiar letter strings (words) from unfamiliar ones (PW’s). Nevertheless, they demonstrated a retained ability to distinguish orthographically regular from orthographically irregular letter strings. That is, they could tell whether or not a letter string could be a word, but they could not decide whether in fact it is a word. Their strategy apparently was to put all potential words into the word pile. Group 2. Like Group 1, these four patients also distinguished orthographically irregular from orthographically regular letter strings, placing no UL into the word pile. Like Group 1, they did not successfully distinguish words from PW’s; they could not use familiarity to make their decisions. Unlike Group 1, the patients in this group did not classify all potential words as words. Instead, they appear to have actively tried to judge the familiarity of the words and PW’s, although their attempts were unsuccessful. Thus, the difference between Groups 1 and 2 may
ORTHOGRAPHIC
KNOWLEDGE
IN APHASIA
311
reflect differences in strategy or in their criteria for calling something ‘ ‘familiar. ’ ’ Group 3. The 11 patients in Group 3 also retained the ability to make use of orthographic rules in sorting the cards. All UL’s were again correctly placed into the nonword pile. These patients demonstrated some ability to make use of familiarity as well, although this ability was impaired. Thus all real words were judged to be familiar by these patients, but some PW’s were judged to be familiar as well. Group 4. The patients in Group 4 clearly demonstrate that they can distinguish words which they have seen before from unfamiliar letter strings. Since they correctly placed all PW’s in the nonword pile, and they were never asked specifically to separate the orthographically regular from the orthographically irregular nonwords, we cannot know for sure whether or not they retain their sensitivity to orthographic regularity. However, there is little reason to suspect that they have lost this ability. They are among the best readers of the 25 patients tested, all of them obtaining combined BDAE reading scores of 30 or better (out of a possible 46). Furthermore, as mentioned earlier, in tachistoscopic tests with normal readers orthographic regularity plays a larger and far more consistent role in affecting the perceptibility of letter strings than does word familiarity (see Massaro, 1975, Chap. 7 for discussion) suggesting a greater sensitivity to this dimension among normal readers. Group 5. Finally, the one patient in Group 5 placed most stimuliregardless of category-into the nonword pile. Thus he showed no evidence of the ability to use either familiarity or orthographic regularity in making his decisions. Nevertheless, it is still quite possible that he retains sensitivity to orthographic regularity. That is, if he were attending only to familiarity (as the task requirements actually demanded), and if his ability to recognize familiar words were impaired, then he might very well end up placing most cards in the nonword pile. As with the patients in Group 4, it is possible that this patient could have performed well were the task to sort potential words from illegal letters strings, rather than real words. Table 2 presents the types of aphasic patients comprising each group, along with the severity rating scores and the symbol discrimination scores of the Boston Diagnostic Aphasia Examination (BDAE). The severity rating score is an indicator of oral communication ability. A score of “0” indicates no usable speech; a score of “5” indicates minimal impairment. The symbol discrimination test, as mentioned above, is a multiple-choice test in which letters and words are to be matched to the same letters and words written in different lettering style-print, script, lower case, upper case. There are 10 trials; hence the range of scores is O-10.
312
RHONDA
B. FRIEDMAN
TABLE BREAKWWN
OF THE DIAGNOSIS
AND ERROR
Group 1 2
3
4
5
RELEVANT PATTERN
2 BDAE
SCORES
FOR EACH
OF THE FIVE
GROUPS
Patient number
Diagnosis
BDAE severity rating
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
global Broca’s anemic global global Wemicke’s Wernicke’s global global global global global global Wemicke’s Wernicke’s Broca’s transcortical sensory “other” nonfluent Wernicke’s anemic conduction conduction “other” nonfluent “other” nonfluent Broca’s
0.5 1.5 1.0 0.0 1.0 1.0 0.0 2.0 1.0 0.0 1.0 0.5 0.5 3.5 1.0 1.0 1.0 0.0 2.5 4.0 2.0 3.0 1.0 0.0 0.5
BDAE symbol discrimination 3 10 9 0 5 10 3 8 8 0 9 10 5 10 5 10 4 9 10 10 9 10 9 10 9
No relationship between error pattern group and diagnostic aphasia category is apparent, and in fact none was predicted. Reading, unlike speech, is not a universal, automatically acquired skill. Instead it is an historically relatively new skill, which is built upon many other preexisting skills of language and visual perception. We would therefore expect it to be more difficult to localize this multifaceted skill. Similarly, there is no consistent relationship between error pattern group and aphasia severity ratings, although the scores of the patients in Group 4 do tend to be on the average higher than those of the other groups. Likewise, the symbol discrimination scores show wide variation within groups, except for Group 4. In short, aside from the observation that the patients with the mildest degree of aphasia may be the least likely to commit any errors at all on the present task, there are no obvious relationships between error patterns on this task and either severity of aphasia or performance on the symbol discrimination task.
ORTHOGRAPHIC
KNOWLEDGE
IN APHASIA
313
CONCLUSION The single most striking aspect of these data is that all 25 of the randomly chosen aphasic patients in this study (with the possible exception of the patient in Group 5) showed convincing evidence of being able to use multiple letter identities to perform some higher-order task. Also of great interest is the manner in which this ability manifests itself in some patients. Even when nonwords could not be distinguished from words, orthographically irregular letter strings were still consistently distinguished from orthographically regular strings. It is important that this result held true across a broad spectrum of aphasia types and severity ratings. It is also significant that this result held true for the five patients (Nos. 1, 4, 7, 10, 17) in this random sample who scored 4 or below (out of 10) on the BDAE symbol discrimination task. This indicates that implicit letter identification can indeed occur in the absence of the ability to explicitly match written letters of the same identity to one another. In sum, while the ability to name written letters may be lost in some aphasic patients, even when word reading remains intact, the ability of aphasic patients to identify written letters may be among the best preserved of all language skills. The symbol discrimination subtest of the BDAE, which is a test of explicit letter recognition, is by far the least difficult of all reading tasks on the BDAE for aphasic patients. The present task takes this further in indicating that knowledge of the orthographic rules of the written language-and by implication implicit letter recognition as well-may be nearly universally preserved among patients with language disturbances caused by dominant hemisphere damage. REFERENCES Albert, M. L. 1979. Alexia. In K. H. Heilman & E. Valenstein (Eds.), Clinical neuropsychology. New York: Oxford Univ. Press. Pp. 59-91. Baron, J., & Thurston, 1. 1973. An analysis of the word superiority effect. Cognitive Psychology,
4, 207-228.
Benson, D. F. 1976. Alexia. In J. T. Guthrie (Ed.), Aspectsof readingacquisition.Ba]timore: Johns Hopkins Press. Pp. 7-36. Benson, D. F., Brown, J., & Tomlinson, E. B. 1971. Varieties of alexia. Neurology, 21, 951-957. Benson, D. F., & Geschwind, N. 1969. The alexias. In P. J. Vi&en & G. W. Bruyn (Eds.), Handbook of clinical neurology. Amsterdam: North-Holland. Vol. 4, pp. 112-140. Gibson, E. J., Pick, A., Osser, H., & Hammond, M. 1962. The role of grapheme-phoneme correspondence in the perception of words. American Journal of Psychology, 75, 554-570. Goodglass, H., & Geschwind, N. 1976. Language disorders. In E. D. Carterette & M. P. Friedman (Eds.), Handbook of perception. New York: Academic Press. Vol. 7, pp. 389-428.
314
RHONDA
B. FRIEDMAN
Goodglass, H., 81 Kaplan, E. 1972. The assessment of aphasia and related disorders. Philadelphia: Lea & Febiger. Massaro, D. W. 197.5. Primary and secondary recognition in reading. In D. W. Massaro (Ed.), Understanding language. New York: Academic Press. Pp. 241-289. Miller, G. A., Bruner, J., & Postman, L. 1954. Familiarity of letter sequences and tachistoscopic identification. Journal of General Psychology, 50, 129-139.
AND
LANGUAGE
14, 307-314 (1981)
Preservation of Orthographic Knowledge in Aphasia RHONDA B. FRIEDMAN Boston
University
School
of Medicine, Medical
and Aphasia Center
Research
Center,
Boston
V.A.
A simple untimed lexical decision task was designed to test implicit letter recognition in aphasic patients. Half of the nonwords used in this task were orthographically regular pronounceable pseudowords, and half were orthographically irregular unpronounceable letter strings. Twenty-five randomly chosen aphasic patients with mild to severe degrees of aphasia participated in the study. Although only six of the patients performed the lexical decision task successfully, all 25 demonstrated the ability to distinguish orthographically regular from irregular letter strings and, by implication, the ability to recognize and make use of the identities of written letters.
Aphasia following damage to the left hemisphere of the brain is usually accompanied by some degree of reading disturbance (Goodglass & Geschwind, 1969). The alexias are often subdivided into two categories, “literal alexia” in which words are read better than letters, and “verbal alexia” in which letters are read better than words (Benson, 1976). Global alexia refers to the total inability to read either words or letters (Albert, 1979). The existence of literal alexia in the absence of verbal alexia may at first seem puzzling. Since it is a particular sequence of letters which uniquely determines a word, it follows that the letters of a word must be identified if the word is to be identified. Closer examination of the phenomenon of literal alexia helps to resolve the apparent contradiction. Although literal alexia is often defined as the inability to “read” or “identify” letters (Benson, Brown, & Tomlinson, 1971), these terms are misleading. What is really deficient in patients said to have literal alexia is the ability to name letters, i.e., the ability to look at a b and call it This work was supported by USPHS Fellowship NS06065 and by USPHS Grant NS06209. I would like to thank Roger Graves, Edgar Zurif, Harold Goodglass, and Marjorie Perlman for their helpful comments. Please address reprint requests to: Dr. Rhonda B. Friedman, Psychology Service (116B), Veterans Administration Medical Center, 150 S. Huntington Avenue, Boston, MA 02130. 307 0093-934X/060307-08$02.00/0 Copyright 0 1981 by Academic Press, Inc. All rights of reproduction in any form reserved.
308
RHONDA
B. FRIEDMAN
a “b.” But it is letter recognition, not letter naming, which is the prerequisite to word identification. Letter recognition, as opposed to letter naming, may be tested by having the patient match upper case letters to lower case letters or print letters to script letters (Benson & Geschwind, 1969); such a test is included in the Boston Diagnostic Aphasia Examination (Goodglass & Kaplan, 1972). This task is a good test of the patient’s ability to recognize isolated letters as familiar symbols. Nevertheless, failure on this task need not indicate an inability to recognize letter identities in other situations. We know that such dissociations exist within other domains of aphasia. For example, a patient who does not respond appropriately to the words eyes or hair within the context of a pointing task may nevertheless respond appropriately to the commands “Close your eyes” and “Comb ‘your hair.” Similarly, it is possible that a patient who fails to demonstrate any recognition of single letters in isolation may nevertheless be able to make decisions based upon letter identity when the letters occur within the context of a letter string. The following experiment tests the degree to which implicit letter recognition-i.e., the ability to use letter identities in making other judgments about letter strings-is retained in the aphasic patient. The task will be one of distinguishing real words from letter strings which do not comprise real words. No explicit letter naming or letter matching is required, nor does the patient have to identify any of the words in the list. The patient’s sole task is to indicate recognition of familiar letter strings (i.e., words). Since words can be distinguished from nonwords only on the basis of the letters of which they are composed, success on this task necessarily implies that successful letter recognition has occurred as well. An additional factor which was built into the study is concerned with the orthographic structure of the nonwords. Much recent research has shown that the adult reader is sensitive not only to the actual “wordness” of a string, but also to its orthographic regularity (Baron & Thurston, 1973; Miller, Bruner, & Postman, 1954) and pronounceability (Gibson, Pick, Osser, & Hammond, 1962). In fact, some authors (Baron & Thurston, 1973; Massaro, 1975) suggest that readers may be more sensitive to orthographic regularity than to familiarity (wordness). Since orthographic regularity may affect performance in some way, half of all nonwords in this task were orthographically regular, and half were not. METHODS Design A stack of 40 cards was placed in front of the patient, each card containing one fourletter string. One-half of the strings were real words; one-fourth were orthographically regular pronounceable nonwords, called “pseudowords” (e.g., felp); and one-fourth were
ORTHOGRAPHIC
KNOWLEDGE
IN APHASIA
309
orthographically irregular, unpronounceable letter strings (e.g., bdxc). The subject was instructed to place all the words in one pile, all the nonwords in a separate pile. This was demonstrated explicitly to the patient with a set of 9 practice items. For patients with comprehension difficulties, a dictionary was employed to aid in explaining the task. The dictionary was shown to the patient and he was asked if he recognized it. All patients readily acknowledged that they knew what the dictionary was. The patient was told to put all those items which were contained within the dictionary on top of the dictionary and all others in a separate place. This was demonstrated with the practice items. Some patients, who for some reason found it difficult or uncomfortable to lift each card and place it into one of the piles, simply pointed to one pile or the other as the examiner held up each card.
Subjects The subjects were 25 aphasic patients on the Aphasia/Neurobehavioral Service of the Boston Veterans Administration Medical Center. There were no special criteria for participation in the study; only those aphasic patients with poor eyesight, evidence of childhood reading difficulties, or an expressed dislike of testing were not asked to participate. The patients spanned a wide range of auditory comprehension and reading abilities. They fell into the following categories of aphasia type, based on clinical evaluations and scores on the Boston Diagnostic Aphasia Examination (Goodglass & Kaplan, 1972): nine global, five Wernicke’s, three Broca’s, three “other” nonfluent aphasias,’ two conduction, two anemic, and one transcortical sensory aphasia.
RESULTS
The number of correct responses for each type of letter string (word, pseudoword, unrelated letter string) was recorded for each patient. A patient was considered to have correctly categorized a letter string type if he placed a significant proportion of the items in the correct pile. The .05 significance levels were determined by binominal test to be the following: 9/10 correct for pseudowords (PW’s) and unrelated letters (UL’s); 15/20 correct for words. Five patterns of results emerged. They are shown in Table 1. The five groups may be characterized as follows: Group 1. The three patients in this group correctly classified the UL’s as nonwords and the words as words, but consistently classified the PW’s incorrectly as words (i.e., placed at least 9 of 10 PW’s into the word pile). Group 2. These four patients performed randomly on words and PW’s, putting some words and some PW’s in each pile, while correctly classifying all UL’s as nonwords. Group 3. Eleven patients correctly classified all UL’s and all words, but performed randomly with PW’s, classifying some as words, some as nonwords. ’ These three patients presented with nonfluent speech typical of Broca’s aphasia. However, Patients 18 and 24 displayed comprehension deficits which were far more severe than the typical Broca’s aphasia patient, while Patient 23 displayed a disproportionately severe anarthria.
310
RHONDA
B. FRIEDMAN
TABLE
1
THE FIVE PATTERNS OF RESULTS
Group
Words
Pseudowords
I
Correct
2 3 4 5
Random Correct Correct Random
Consistently incorrect Random Random Correct Correct
Unrelated letters Correct Correct Correct Correct Correct
Group 4. The six patients in this group correctly classified all three types of letter strings; that is, they put the real words in one pile, and the PW’s and UL’s in another. Group 5. One patient placed all the UL’s and PW’s in the nonword pile, yet failed to consistently place all words in the correct pile. The different error patterns are suggestive of different degrees of impairment in the ability to recognize two separate types of properties of letter strings-familiarity (have I seen this letter string before?) and orthographic regularity (does this letter string conform to the orthographic rules of the language?). The task required the patient to classify solely on the basis of familiarity; the patient was never specifically asked to attend to orthographic regularity. Yet when the task was failed, incorrect responses appeared to reflect decisions based upon orthographic regularity rather than pure guessing. The five groups of error patterns are discussed below with regard to the factors of familiarity and orthographic regularity. Group 2. The consistent but incorrect placement of PW’s into the word pile by these patients indicates a breakdown in the ability to distinguish familiar letter strings (words) from unfamiliar ones (PW’s). Nevertheless, they demonstrated a retained ability to distinguish orthographically regular from orthographically irregular letter strings. That is, they could tell whether or not a letter string could be a word, but they could not decide whether in fact it is a word. Their strategy apparently was to put all potential words into the word pile. Group 2. Like Group 1, these four patients also distinguished orthographically irregular from orthographically regular letter strings, placing no UL into the word pile. Like Group 1, they did not successfully distinguish words from PW’s; they could not use familiarity to make their decisions. Unlike Group 1, the patients in this group did not classify all potential words as words. Instead, they appear to have actively tried to judge the familiarity of the words and PW’s, although their attempts were unsuccessful. Thus, the difference between Groups 1 and 2 may
ORTHOGRAPHIC
KNOWLEDGE
IN APHASIA
311
reflect differences in strategy or in their criteria for calling something ‘ ‘familiar. ’ ’ Group 3. The 11 patients in Group 3 also retained the ability to make use of orthographic rules in sorting the cards. All UL’s were again correctly placed into the nonword pile. These patients demonstrated some ability to make use of familiarity as well, although this ability was impaired. Thus all real words were judged to be familiar by these patients, but some PW’s were judged to be familiar as well. Group 4. The patients in Group 4 clearly demonstrate that they can distinguish words which they have seen before from unfamiliar letter strings. Since they correctly placed all PW’s in the nonword pile, and they were never asked specifically to separate the orthographically regular from the orthographically irregular nonwords, we cannot know for sure whether or not they retain their sensitivity to orthographic regularity. However, there is little reason to suspect that they have lost this ability. They are among the best readers of the 25 patients tested, all of them obtaining combined BDAE reading scores of 30 or better (out of a possible 46). Furthermore, as mentioned earlier, in tachistoscopic tests with normal readers orthographic regularity plays a larger and far more consistent role in affecting the perceptibility of letter strings than does word familiarity (see Massaro, 1975, Chap. 7 for discussion) suggesting a greater sensitivity to this dimension among normal readers. Group 5. Finally, the one patient in Group 5 placed most stimuliregardless of category-into the nonword pile. Thus he showed no evidence of the ability to use either familiarity or orthographic regularity in making his decisions. Nevertheless, it is still quite possible that he retains sensitivity to orthographic regularity. That is, if he were attending only to familiarity (as the task requirements actually demanded), and if his ability to recognize familiar words were impaired, then he might very well end up placing most cards in the nonword pile. As with the patients in Group 4, it is possible that this patient could have performed well were the task to sort potential words from illegal letters strings, rather than real words. Table 2 presents the types of aphasic patients comprising each group, along with the severity rating scores and the symbol discrimination scores of the Boston Diagnostic Aphasia Examination (BDAE). The severity rating score is an indicator of oral communication ability. A score of “0” indicates no usable speech; a score of “5” indicates minimal impairment. The symbol discrimination test, as mentioned above, is a multiple-choice test in which letters and words are to be matched to the same letters and words written in different lettering style-print, script, lower case, upper case. There are 10 trials; hence the range of scores is O-10.
312
RHONDA
B. FRIEDMAN
TABLE BREAKWWN
OF THE DIAGNOSIS
AND ERROR
Group 1 2
3
4
5
RELEVANT PATTERN
2 BDAE
SCORES
FOR EACH
OF THE FIVE
GROUPS
Patient number
Diagnosis
BDAE severity rating
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
global Broca’s anemic global global Wemicke’s Wernicke’s global global global global global global Wemicke’s Wernicke’s Broca’s transcortical sensory “other” nonfluent Wernicke’s anemic conduction conduction “other” nonfluent “other” nonfluent Broca’s
0.5 1.5 1.0 0.0 1.0 1.0 0.0 2.0 1.0 0.0 1.0 0.5 0.5 3.5 1.0 1.0 1.0 0.0 2.5 4.0 2.0 3.0 1.0 0.0 0.5
BDAE symbol discrimination 3 10 9 0 5 10 3 8 8 0 9 10 5 10 5 10 4 9 10 10 9 10 9 10 9
No relationship between error pattern group and diagnostic aphasia category is apparent, and in fact none was predicted. Reading, unlike speech, is not a universal, automatically acquired skill. Instead it is an historically relatively new skill, which is built upon many other preexisting skills of language and visual perception. We would therefore expect it to be more difficult to localize this multifaceted skill. Similarly, there is no consistent relationship between error pattern group and aphasia severity ratings, although the scores of the patients in Group 4 do tend to be on the average higher than those of the other groups. Likewise, the symbol discrimination scores show wide variation within groups, except for Group 4. In short, aside from the observation that the patients with the mildest degree of aphasia may be the least likely to commit any errors at all on the present task, there are no obvious relationships between error patterns on this task and either severity of aphasia or performance on the symbol discrimination task.
ORTHOGRAPHIC
KNOWLEDGE
IN APHASIA
313
CONCLUSION The single most striking aspect of these data is that all 25 of the randomly chosen aphasic patients in this study (with the possible exception of the patient in Group 5) showed convincing evidence of being able to use multiple letter identities to perform some higher-order task. Also of great interest is the manner in which this ability manifests itself in some patients. Even when nonwords could not be distinguished from words, orthographically irregular letter strings were still consistently distinguished from orthographically regular strings. It is important that this result held true across a broad spectrum of aphasia types and severity ratings. It is also significant that this result held true for the five patients (Nos. 1, 4, 7, 10, 17) in this random sample who scored 4 or below (out of 10) on the BDAE symbol discrimination task. This indicates that implicit letter identification can indeed occur in the absence of the ability to explicitly match written letters of the same identity to one another. In sum, while the ability to name written letters may be lost in some aphasic patients, even when word reading remains intact, the ability of aphasic patients to identify written letters may be among the best preserved of all language skills. The symbol discrimination subtest of the BDAE, which is a test of explicit letter recognition, is by far the least difficult of all reading tasks on the BDAE for aphasic patients. The present task takes this further in indicating that knowledge of the orthographic rules of the written language-and by implication implicit letter recognition as well-may be nearly universally preserved among patients with language disturbances caused by dominant hemisphere damage. REFERENCES Albert, M. L. 1979. Alexia. In K. H. Heilman & E. Valenstein (Eds.), Clinical neuropsychology. New York: Oxford Univ. Press. Pp. 59-91. Baron, J., & Thurston, 1. 1973. An analysis of the word superiority effect. Cognitive Psychology,
4, 207-228.
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