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Impaired activation of the phonological lexicon: Effects upon oral reading
BRAIN
AND
LANGUAGE
38,
278-297
(I!?%)
impaired Activation of the Phonological Lexicon: Effects upon Oral Reading RHONDA B. FRIEDMAN Aphasia Research Center, Department of Neurology, Boston University School of Medicine; and Cognitive Neuroscience Unit, Medical Neurology Branch, NIH/NINDS AND SUSAN E. KOHN Neurolinguistics Laboratory, Institute of Health Professions, Massachusetts General Hospital, and Department of Neurology, Harvard Medical School The role of the phonological lexicon in oral reading is examined in a patient with a small focal left hemisphere lesion. Impaired access to the patient’s phonological lexicon is suggested by a number of findings, including the production of phonemic errors across a variety of tasks; increasing difficulty in word production with increasing word length; and difficulty on tests of homophone and rhyme judgments. Two competing models of reading are tested: the nonlexical (“rules”) and the lexical (“no-rules”) mbdels. The rules model predicts that a disturbance in the phonological lexicon will result in surface alexia; the no-rules model predicts phonological alexia. Results indicate that the patient’s reading is most similar to phonological alexia, providing support for the no-rules model. The applicability of the no-rules model to other forms of acquired alexia is explored. 0 1990 Academic Press. Inc.
The phonological lexicon is a standard feature of current models of language processing (e.g., Caramazza, Miceii, & Villa, 1986; Patterson & Shewell, 1987). Every word (or morpheme) in a person’s vocabulary is stored in this lexicon in the form of a phonological representation, consisting of information about its syllabic structure and phonemic content (Caplan, Vanier, & Baker, 1986; Kohn, 1985). This lexicon is said to be used in oral reading, spontaneous speech, naming (Margolin, MarThis work was supported in part by USPHS Grant NSO6209. Reprint requests should be addressed to Dr. Rhonda B. Friedman, Cognitive Neuroscience Unit, NIH/NINDS, Bldg. 10 Rm. 5C-422, Bethesda, MD 20892. 278 0093-934x&O $3.00 Copyright All rights
0 1990 by Academic Press. Inc of reproduction in any form reserved.
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ccl, & Carlson, 1985), and repetition (Caplan et al., 1986; Kay & Patterson, 1985). It follows that impaired access to the phonological representations in the lexicon should affect all of these language activities, resulting in qualitatively similar errors across these activities. Errors would be expected to occur along the parameters encoded in these representations. In particular, phonemic paraphasias should be produced in all such contexts, and there should be an effect of word length such that the number of errors increases as the number of syllables in words increases (e.g., Caplan et al., 1986). Further characterization of the quality of oral reading following impairment to the phonological lexicon depends upon the type of reading model consulted. According to one popular model, depicted in Fig. 1, the pronunciation of a written word may be obtained by consulting the lexicon, or it may be obtained nonlexically, through the use of a system of orthography-to-phonology conversion rules (e.g., Caramazza et al., 1986; Patterson and Shewell, 1987). Impaired access to the phonological lexicon would force reliance upon the nonlexical reading route, and the quality of the resultant reading would depend upon the characteristics of this nonlexical pathway. Since this route is rule-driven, we would expect oral reading errors on words whose pronunciations do not follow the rules of orthography-to-phonology conversion (i.e., irregular words). The types of reading errors that we should see are errors that are the result of a rule-guided strategy, i.e., “regularization” errors. For exwritten word I I c--
i
---------
letter identification
grapheme to phoneme convysion I I I
i
L,,--,,+ FIG.
spoken word
1. The “rules”
model of single word reading.
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ample, when applying the long-vowel-silent-e rule to the irregular word come, the result is “comb.” This pattern of reading, in which irregular words are read incorrectly while regular words are read correctly, and where regularization errors are produced, is called “surface alexia” (e.g., Kay & Lesser, 1985). A corollary feature of surface alexia is good performance on reading orthographically legal pseudowords such as hote. In addition, frequency should not be a factor in the pure form of this alexia, at least for regular words, since the orthography-to-phonology rules apply to words of any frequency, including zero frequency (i.e., pseudowords). Thus, according to Model 1, which we shall call the “rules” model, a patient with damaged access to the phonological lexicon should show a reading profile consistent with surface alexia (cf. Margolin et al., 1985). Reading of nonwords and regular real words should be relatively preserved; reading of irregular real words should be poor, and should result in regularization errors. Word frequency effects should not be found. According to the reading model depicted in Fig. 2, quite a different picture would be expected with impaired access to the phonological lexicon. This model does not include a nonlexical reading route. The reading of all words-and pseudowords-utilizes the phonological entries stored in the lexicon. When a letter string is viewed, the corresponding entry in the orthographic lexicon is aroused. In addition, orthographically similar “neighborhood” entries are aroused. The entry that is an exact match with the stimulus receives maximal activation; neighborhood written word I i letter identification
spoken word FIG.
2.
The “no-rules”
model of single word reading.
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words receive only partial activation. If there is no exact match in the orthographic lexicon-either because the subject is unfamiliar with the word or because it is, in fact, a pseudoword-then no one orthographic entry receives maximal activation. A pronunciation is derived from the partially activated neighborhood words, in a process of “analogy” (Glushko, 1979, 1981; Kay & Marcel, 1981), although the exact procedures by which this occurs are unclear. For example, the pseudoword bin might activate the real words him, hit, pin, and sin. These partially activated words combine to yield the composite pronunciation “hin.” If this “no-rules” model is correct, then what pattern of oral reading would we expect if the phonological lexicon were not activated properly? Recall that in this model, the reading of all words-real regular words, real irregular words, and pseudowords-depends upon proper activation of the phonological lexicon; no alternate pathway exists. Impaired access to the phonological lexicon, then, would affect the reading of both pseudowords and real words. Irregular words should present no particular difficulty relative to regular words. Frequency effects would be likely, since all reading is still occurring through the phonological lexicon: It is likely that high frequency words have stronger representations (or higher resting levels of activation (Miller & Ellis, 1987)), and hence are less likely to be affected when the system is damaged than are low-frequency, more weakly represented words. More specific effects of impaired access to the phonological lexicon in Model 2 can be illustrated by considering the consequences of reduced probabilities of activating lexical entries. Pseudoword reading depends upon the correct activation of all neighborhood words. If any neighborhood words are not properly activated, pseudoword pronunciation will be affected. By contrast, real words do not require that all neighborhood words be activated, so long as the specific target word receives maximal activation. Let us suppose that a processing deficit has reduced the probability of correctly activating a phonological code to .X. Now any given real word has the probability .X of becoming fully activated. Pseudowords, however, depend upon the combined activation of N neighborhood words. The probability that all of those words will be activated correctly is .X to the Nth power, a probability that is lower than .X, and gets lower as the number of needed neighborhood words, N, increases. Thus, according to the “no-rules” model, when activation of the phonological lexicon is impaired we expect to see a decrement in the reading of real words, and a substantially greater decrement in the reading of pseudowords. This pattern most closely resembles “phonological alexia. ” Thus, the “rules” model and the “no-rules” model yield very different predictions about the expected pattern of reading following impaired activation of the phonological lexicon. The first model predicts surface
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alexia; the second model predicts phonological alexia. To test these two models, we present the case of a patient for whom access to the phonological lexicon is impaired following neurological damage, as evidenced by similar deficits in oral reading, picture naming, and repetition. His oral reading performance was examined with respect to those variables that differentiate surface and phonological alexia, i.e., effects of regularity, production of regularization errors, pseudoword reading ability, and effects of word frequency and word length. HISTORY H.R. is a 52-year-old right-handed attorney who suffered a left cerebrovascular accident subsequent to a myocardial infarction. He initially presented with right-sided weakness and difficulty speaking. No further details about his acute condition are available. At the time of experimental testing, a mild right hemiparesis was present. H.R. returned to work as an attorney part time, and continued to receive speech therapy. A CT scan 1 month post-onset revealed a patchy lesion involving the temporal isthmus, the posterior half of Wernicke’s area, and the posterior supramarginal and angular gyri . A language examination 1 year post-onset indicated that H.R.‘s speech was fluent and well articulated. He had moderate word-finding difficulties, and he produced phonemic paraphasias which were often self-corrected. Auditory comprehension was very good. Repetition and naming were poor. Writing and oral reading were quite impaired; however, H.R.‘s reading comprehension on the Boston Diagnostic Aphasia Exam (BDAE) (Goodglass & Kaplan, 1983) was consistently good. Furthermore, he frequently provided excellent definitions for words that he could not read aloud. To further test his comprehension of single words, we constructed 36 pairs of visually similar low frequency words. For each pair, we read aloud the definition of one of the words. H.R.‘s task was to point to the written word corresponding to the spoken definition. He scored 33/36 on this task. At three years post-onset, H.R.‘s aphasia profile remained unchanged, except for some improvement in word-finding ability (Table 1). TESTS OF THE INTEGRITY
OF THE PHONOLOGICAL
LEXICON
The following tests involve accessing the phonological lexicon from different input routes. The results of these tests provide evidence for the proposition that H.R.‘s language difficulties are best attributed to a breakdown in accessing the phonological lexicon. Single Word Production As noted earlier, it is expected that disrupted access to information within the phonological lexicon should have a similar effect upon per-
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TABLE 1 BDAE SCORES (PERCENTILES) Years post-onset
Subtest Responsive Naming Confrontation Naming Animal Naming Repetition, words Repetition, high-probability Repetition, low-probability
sentences sentences
1
3
60 45 60
75 68 70
30 20 50
40 50 50
Auditory comprehension, ideational material
complex
90
Reading comprehension, and paragraphs
sentences
95
formance on all tests of single-word oral production, and in ways that can be characterized in terms of phonological properties of the target words. In order to examine H.R.‘s ability to access stored phonological representations for oral production along different routes into the phonological lexicon, his oral production of single words was tested in the following paradigms: (1) picture naming, which involves access to the phonological lexicon via the semantic lexicon, (2) oral reading, which involves access to the phonological lexicon via the orthographic lexicon, and (3) repetition, which can involve access to the phonological lexicon via acoustic phonetic input. All responses were tape recorded and transcribed for accurate error analysis. Unless otherwise noted, tests were administered at 1.5 to 2.5 years post-onset. Picture naming vs. oral reading. To compare H.R.‘s ability to produce the name of a word from a written stimulus and from a pictured stimulus, we constructed a list of 52 picturable nouns, varying in length from one to four syllables. The list was divided into two 26-item lists. On 1 day, H.R. was asked to name the pictures corresponding to one list of nouns, and to read the words corresponding to the other list of nouns. Two weeks later he was asked to name the pictures corresponding to the second list and to read the words corresponding to the first list. The results are presented in Fig. 3. On both tests, H.R. had more difficulty in correctly producing the target words as they increased in number of syllables. (There were no statistical differences between the two tasks.) On both tests, incorrect attempts were typically phonologically related to their targets. A phonologically related attempt was defined as a re-
FRIEDMAN
AND KOHN
n 1 syllable q 2 syllable 3 syllable
q
word
reading
picture
4 syllable
naming
Task FIG.
3. Word reading versus picture naming, by number of syllables.
sponse that matched its target word in terms of at least a consonant cluster (e.g., sled ---, “slight”), a stressed vowel (e.g., kangaroo ---, “goo”), or the onset and coda of a syllable (e.g., envelope + “lop”) (Kohn, 1985). The tendency to produce phonologically related (incorrect) responses was quantified as the proportion of incorrect trials that involved at least one phonologically related response. In the picture naming condition, 75% (21/28) of H.R.‘s incorrect trials involved such phonological errors. In the reading condition, 87% (20/23) of his incorrect trials involved phonological errors. (See appendix for more examples of errors that are classified as phonological as well as some nonphonological errors.) Repetition vs. oral reading. To compare H.R.‘s ability to produce the name of a word from a written and a spoken stimulus, we constructed a separate list of 28 picturable nouns ranging in length from one to three syllables. Results are presented in Fig. 4. As with the previous production data, there is an effect of number of syllables for both conditions. The overall level of performance for repetition and reading trials is quite similar (repetition, 68%; reading, 71%). In order to obtain a large enough corpus of incorrect responses to examine H.R.‘s pattern of errors during repetition, a separate set of 40 concrete nouns ranging in length from one to three syllables was presented. Performance on this test resembled performance on the previous repetition test. He correctly repeated 75% of the target words and had more difficulty as target words increased in number of syllables (one syllable, 95%; two syllables, 86%; three syllables, 43%). All (100%) of
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n q 0
1 syllable
2 syllable 3 syllable
0 repetition
reading
Task FIG. 4. Repetition versus reading, by number of syllables.
his incorrect responses involved a phonologically related attempt (as defined above). Summary. Across the three conditions of single-word oral production, H.R.‘s performance was quite similar in terms of the strong tendency for errors to involve phonological distortions of the target word and for such errors to increase as words increased in length. The results clearly demonstrate that H.R. has a general phonological deficit that impairs his oral production under various conditions. Moreover, these results are consistent with the notion that the deficit responsible for H.R.‘s wordproduction difficulty involves access to the phonological lexicon. Reading
Errors that Reject
Activation
of Multiple
Representations
A rather dramatic demonstration of the failure to activate the precise phonological code for a word occurred on trials in which H.R., unable to provide a correct pronunciation for a written word, gave a definition instead. On occasion, H.R. would produce multiple definitions for polysemous words. For example, he gave four different (correct) definitions of the word mercury. Of particular interest were those trials in which he gave two definitions for a written word-one of which was not correct. For example, sky, which was not read aloud correctly, elicited the following definitions: “That thing up there with the clouds” and “Sometimes you get one under your eye”. Apparently, both sky and sty had become activated in the orthographic lexicon, and the appropriate semantic representations for each word had subsequently been activated. H.R. was unable to access the lexical phonological information needed to tell him that sky and sty are different words; presumably, he assumed
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that he was presented with another of the many polysemous words of English. Similar confusions were made by H.R. between slate/state, galley/gallery, and continent/countenance. We believe that such multiple activations occasionally occur among normal readers as well, but the activation of two disparate phonological codes alerts the normal reader to the likelihood that this is not correct.’ Tests of Homophone
and Rhyme Judgement
The following tests of homophone and rhyme judgement were administered in order to assess H.R.‘s ability to access phonological representations within the lexicon without the confounds of a possible output problem (cf. Kohn, Schonle, & Hawkins, 1984). In order to determine if two written words are rhymes or homophones (especially if irregular spelling is involved), the reader must first access the stored orthographic representations and then their corresponding phonological representations to determine if the two phonological representations match (i.e., correspond to similar patterns of activation in the phonological lexicon). Similarly, in order to determine whether the names of two pictures are rhymes or homophones, the stored phonological representations of the pictures’ names must be compared. These tests do not require such components of phonological production as phonemic string construction or a phonemic output buffer for accurate performance (cf. Kohn, 1989). Trials for the tests of homophone and rhyme judgements were presented to H.R. individually on index cards. Homophone matching. H.R. was asked to identify written homophones under several different conditions. To determine the extent to which H.R. could identify homophones using lexical representations (as opposed to grapheme-phoneme conversion rules), he was given a test where many of the words contained spellings with ambiguous pronunciations. Specifically, he was asked to decide whether two written words were homophones, where positive and negative pairs were matched for visual similarity (e.g., doe-dough; toe-tough). On this 84-item test, there was an equal number of pairs with one- and two-syllable words. H.R. was correct on 74% of the trials (80% on homophone pairs; 61% on nonhomophone pairs). In another task, H.R. had to match a written word to its corresponding homophone from among four written choices. All written words were ’ As one reviewer pointed out, it is possible that normal readers never arouse incorrect orthographic lexical entries, and that these errors produced by H.R. reflect an impairment of the orthographic lexicon itself. While this is possible, the small number of words that were missed in this fashion suggest to us that H.R. does not have such a deficit. In any case, the fact remains that H.R. cannot disambiguate the words using phonological information.
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single syllable and ranged from three to five letters. Foils were rhymes and alliterations (e.g., sail: mail, salt, said, sale). He scored 86% correct. Finally, H.R. was given a more difficult four-choice test of homophone matching. In this test not every trial contained a homophone among the choices. In this way, we could be sure that he was searching for complete phonological identity between words, and not simply the closest phonological match. H.R. was instructed to make sure that the word chosen was not only the best choice, but a perfect match. If no match appeared among the choices, he was instructed to say so. This test had 30 trials, 10 of which contained no homophones. As with the previous multiplechoice test, all words were single syllable with three to five letters, and foils were rhymes and alliterations. H.R. scored 73% correct. Rhyming. As with the homophone judgements, H.R.‘s ability to detect rhymes was assessed in several ways. However, before these tests were administered, we determined that he understood the concept of a rhyme in the following manner. H.R. was given a spoken word, followed by three spoken words that rhyme with the target word. After each of these words was spoken, he was told that the word rhymes with the initial target word. He was then presented with 11 spoken words. After each word, he was asked if that word rhymed with the target word. This procedure was repeated for a second target word. H.R.‘s yes-no decision was correct for all 22 items, 10 yes’s and I2 no’s H.R. was next presented with pairs of written words and asked to determine whether each pair rhymed. There were 50 pairs of visually similar words. Half of the pairs were rhymes (past-cast), while the remaining nonrhyme pairs were constructed so that they were analogous to the rhyming pairs (paste-caste). Thus, as with the homophone test involving word pairs, many words involved ambiguous spellings. H.R. was successful on 70% of the trials (20/25 rhymes; 15/25 nonrhymes). This level of performance indicates that he can do the task, but that on a large number of trials he does not have sufficient phonological information about the two words to make the correct choice. H.R. was given one other test of rhyme judgement that was more difficult insofar as it increased processing demands within the phonological lexicon. A multiple choice task was employed to examine H.R.‘s ability to determine whether the names of various pictures rhyme with one another. On each of 15 trials there was a target picture, and three choice pictures. The names of each of the three choice pictures began with the same letter and differed either in the vowel or in the final consonant (e.g., CAN pin pan pail). All stimulus names were single syllable. H.R.‘s task was to choose the picture whose name rhymes with the name of the target picture. He scored 6/15, which is not above chance on this task. Summary. H.R.‘s performance on tests of homophone and rhyme
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judgements matched the expectations for impaired access to the phonological lexicon. Insofar as such tests involve the evaluation of stored phonological representations, his impaired performance on such tests can be interpreted as evidence for impaired lexical phonological access. TESTS OF SINGLE WORD ORAL READING The following tests of reading are typically used when assessing acquired disorders of reading, in order to fully characterize the type of reading impairment present: tests of the effects of regularity, part of speech, concreteness, frequency, and word length; tests of pseudoword reading; and examination of the types of errors produced. Of particular interest here are those that distinguish between surface and phonological alexia. Specifically, patients with surface alexia should read pseudowords well, should show an effect of regularity, and should produce regularization errors. Patients with phonological alexia should read pseudowords poorly, show no effect of regularity, and produce no regularization errors. Unless stated otherwise, the tests reported in this section were administered approximately 1.5 years post-onset. Pseudowords H.R. was asked to read 180 one-syllable pseudowords (PWs). He read only 7% correctly. Similar to his errors on real word reading, 82% of the errors he produced on PW reading bore phonological resemblance to the target pseudowords (e.g., hocks + /blap/; cheef + /tJit/). (The definition of phonological similarity that we used can be found in the discussion of picture naming, above.) Regularity Twenty-five regular words (e.g., chess) and 25 irregular words (e.g., chef) were presented to H,.R. for oral reading. He read 14 of the regular words, and 17 of the irregular words. Eighteen months later, H.R. was asked to read a new list of 20 regular and 20 exception words. Half of the words in each list were high frequency; half were low frequency. The results, presented in Fig. 5, show no effects of regularity, but a striking effect of frequency. Regularization Errors In examining for paralexic responses that could be classified as “regularization errors”, i.e., errors that appear to be the result of correctly applying spelling-to-sound correspondence rules in the wrong context, we attempted to use as large a pool of oral reading responses as possible. Consequently we pooled together the responses produced on many oral reading tests, spanning many months. Of the 622 paralexic errors that were found in this pool of words, only 1% could be considered regu-
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Q
high frequency
+
low frequency
.> regular
irregular
Regularity FIG. 5. Word reading: Effects of regularity versus frequency.
larization errors. Note that all of these errors (e.g., LOOSE -+ “news”; put + “putt”; plan --, “plane”) could very well be considered phonological errors as well. (Compare with these phonological errors, which cannot be considered regularizations: butter-y -+ /bct&le/, snowman + /snuman/.) Part of Speech An oral reading test containing equal numbers of concrete nouns, abstract nouns, adjectives, verbs, and three kinds of functors failed to demonstrate any effect of part of speech. In a separate test of functor word reading, 21 pairs of functor-nonfunctor homophones (be/bee, or/oar) were presented to H.R. In this task, which fully equates phonological complexity, H.R. scored 16/21 on functors, 17/21 on nonfunctors. Eighteen months later H.R. was. asked to read 305 words of 3-8 letters. Words were matched across part of speech for number of syllables, number of letters, and whether or not the first letter of the word is a vowel. Within the constraints outlined, words were chosen to be as high in frequency as possible. H.R.‘s scores were as follows: Concrete nouns, 53; abstract nouns, 53; adjectives, 53; verbs, 54; functors, 46. Taken together, these results indicate no part of speech effects in H.R.‘s oral reading, other than a possible weak, unreliable tendency for functors to be read less efficiently than content words. Concreteness In the first test for part-of-speech effects, the nouns were divided into those that are abstract and those that are concrete. All 10 concrete nouns
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were read correctly; 7 of the 10 abstract nouns were read correctly. We pursued this factor further by administering another test of oral reading of nouns 2 months later. On this test H.R. read 11/15 concrete nouns and 7/15 abstract nouns. As before, there was a nonsignificant tendency towards reading concrete nouns better than abstract nouns (x2 = 1.25). One year later, a list of 30 concrete and 30 abstract nouns was administered. H.R. read 25/30 concrete nouns and 15/30 abstract nouns. This difference is significant (x2 = 6.075, u” = 1, p < .02). Around the same time, H.R. was asked to read M. Coltheart’s list of 28 high imageability and 28 low imageability words. Imageability is highly correlated with concreteness (Paivio, Yuille, & Madigan, 1968), and some authors believe that it is the effect of imageability, not concreteness per se, that is sometimes seen in brain-damaged patients. H.R. read 12/28 high imageability and 12/28 low imageability words. One-half year later, the 305-word parts of speech list mentioned above was given to H.R. for oral reading. As noted, H.R. successfully read 53 of the concrete and 53 of the abstract nouns. In a final attempt to determine whether or not an effect of concreteness can be seen in H.R.‘s reading, a list of 75 concrete and 75 abstract words (40 high frequency pairs; 35 low frequency pairs) was presented to H.R. for oral reading. Results can be seen in Fig. 6. While there is a large effect of frequency, no effect of concreteness can be detected. The combined results of these five tests indicate that the concreteness variable was not a reliable factor in H.R.‘s reading performance.
100
”
.
~~~
Q
high
+
low frequency
frequency
1
concrete
abskxt
Concreteness FIG.
6. Word reading: Effects of concreteness versus frequency.
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AND
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READING
Frequency H.R. was asked to read a list of 48 words of one to three syllables, matched for length across frequency. He correctly read 6/16 high frequency, 4/16 middle frequency, and 2/16 low frequency words on the first attempt. The number of words read correctly given unlimited attempts was 1l/16,7/16, and 4/16 for the high, middle, and low frequency words, respectively. The effect of frequency on H.R.‘s oral reading remained strong 18 months later. On one test of concreteness and on a separate test of the effects of regularity H.R.‘s reading was greatly affected by frequency. (See sections on Regularity and Concreteness; Figs. 5 and 6). Word Length The first test given to H.R. for the assessment of effects of word length consisted of 40 nouns. His accuracy on words of 3, 5, 7, and 9 letters, respectively, was 78, 80. 44, and 17%. When broken down by number of syllables, the results for 1, 2, 3, and 4 syllable words were 78, 63, 15, and O%, respectively. In a second, more controlled test of word length, H.R.‘s scores on 4, 6-, and S-letter words were 100, 73, and 30%, respectively. He read 90% of the one-syllable, 67% of the two-syllable, and 50% of the three-syllable words. To take a closer look at the effects of number of letters vs. number of syllables, we looked at H.R.‘s reading of 40 nouns. There were five words in each of eight syllable X letter combinations. As can be seen in Table 2, it is the number of syllables, not the number of letters, that affects H.R.‘s performance.
TABLE PROPORTION
OF WORDS
READ NUMBER
2
CORRECTLY,
BY NUMBER
Number
Number 1 2 3 4
Nofe.
OF LETTERS
AND
OF SYLLABLES
of letters
3-4
5-6
l-8
.6 .2 0.40
.8 .4 0.0 0.40
.2 0.0 0.0 0.07
of syllables
n = 5 words
per cell.
0.70 0.27 0.00 0.00
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DISCUSSION The purpose of this case study was two-fold: (1) to demonstrate that H.R.‘s oral production and reading deficits reflect a deficit in accessing the phonological lexicon and (2) to determine which of two lexical models best accounts for this pattern of behavior. Model 1, which includes a system of nonlexical orthography-to-phonology conversion rules, predicts surface alexia following disturbed activation of the phonological lexicon. Model 2, whose only route to reading is through lexical access, predicts phonological alexia. It is clear that H.R. has a phonological deficit that affects oral production in all contexts. Across tests of oral reading, repetition, and picture naming, errors were consistently phonologically related to targets, and performance was affected by the number of syllables in the targets. This phonological deficit appears to involve impaired access to the phonological lexicon, as opposed to a postlexical output deficit. This is supported by his poor performance on tests that require access to stored phonological representations without requiring a spoken response, such as homophone and rhyme judgements. His unusual reading errors, in which activation of two phonologically similar words goes unnoticed, is further evidence that lexical phonology is not properly accessed. In tests of oral reading, we found no evidence of surface alexia. H.R. displayed a severe deficit in reading pseudowords, a milder deficit in reading real words, no regularization errors, and no effect of regularity. Thus, Model 1, the “rules” model, is not supported. Instead, this reading performance most resembles phonological alexia, supporting the prediction of Model 2, the “no-rules” model. This interpretation is based upon the assumption that we are dealing with a single functional deficit. Parsimony favors the explanation that relies on the fewest deficits to account for the data. Still, it is possible for Model 1 to account for the data by claiming that H.R. has two functional deficits, one in accessing the phonological lexicon and a more severe deficit in the “indirect” rule-driven reading route. It is of course difficult to disprove a two-deficit hypothesis for H.R. Nonetheless, if H.R. does have two separate deficits, then we should expect to see some patients who have only a deficit in accessing the phonological lexicon. Such patients, according to Model 1, should have surface alexia. Are there any such cases in the literature? The edited volume Surface Dyslexia (Patterson, Marshall, & Coltheart, 1985) provides several potential candidates. Margolin et al. (1985) present the case of R.F. whose’ oral reading and picture naming are impaired. The authors conclude that “entries in R.F.‘s phonological lexicon are of reduced accessibility” (p. 151). Does R.F. read like a surface alexic or a phonological alexic? Surface alexics, by definition, show an effect
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of regularity and read pseudowords well. In oral reading of real words R.F. does not show a significant effect of regularity, and her oral reading of pseudowords is poor. The authors argue, despite these findings, that R.F. should nevertheless be considered a surface alexic because she appears to be using a “sublexical strategy” for reading. However, by all objective criteria, R.F.‘s reading is more consistent with phonological alexia. In the same volume, Kay and Patterson (1985) present a patient, E.S.T., who had difficulties in reading, picture naming, and spontaneous speech following removal of a meningioma. The authors claim that “the primary impairment in E.S.T.‘s case is in gaining access to lexical phonology” (p. 99). Although E.S.T. produced regularization errors, his reading of irregular words was not significantly worse than regular words. He read 84% of pseudowords using an “acceptable” pronunciation: his responses were often correct by analogy but not by strict application of spelling-to-sound correspondence rules. This patient does not fit neatly into either category of surface or phonological alexia. A potential problem in interpreting this case is that effects of number of syllables were not measured-a critical variable for identifying breakdown within the phonological lexicon. Another problem is that both auditory comprehension and reading comprehension were impaired. These multiple deficits call into question the assertion that E.S.T.‘s difficulties are strictly the result of problems within the phonological lexicon. Thus this case also fails to demonstrate surface alexia that is solely caused by a disturbance in the phonological lexicon. Goldblum’s (1985) case of “postsemantic” surface alexia, in the same volume, is also attributed to a disturbance within the phonological lexicon. However, the patient showed no effect of number of syllables on word reading; picture naming that was superior to oral reading; and a difference in the quality of production errors between these two tasks. These findings suggest a word-finding impairment specific to reading, rather than a general problem with the phonological lexicon. Finally, the patient of Kremin (1985), described as a surface alexic with phonological disruption, may be a good example of surface alexia, but she does not appear to have a deficit within the phonological lexicon. She had difficulty with oral reading and picture naming and she read regular words more accurately than irregular words. Her level of pseudoword reading was relatively high, 72%. However, there was no effect of number of syllables for naming, and a questionable effect for oral word reading. In addition, her performance on a rather difficult written homophone matching test was excellent. This pattern of performance suggests that she does have relatively intact access to the phonological codes for lexical items. We have thus failed to uncover any convincing evidence that an iso-
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lated deficit in accessing the phonological lexicon can produce surface alexia. Consequently, at present we reject the less parsimonious interpretation that H.R.‘s problems are the result of two separate functional deficits and reaffirm our conviction that all of his deficits can be attributed to the disturbance of a single underlying mechanism-activation of the phonological lexicon. In describing the pattern of reading deficits displayed by H.R., we have demonstrated one way that phonological alexia might be produced within the framework of the “no-rules” model, i.e., disruption to the phonological lexicon. The question remains as to how well this model accounts for other reading disorders. For example, phonological alexia has also been reported in patients for whom activation of the phonological lexicon does not appear to be impaired (Beauvois and Derouesne, 1979). How does the no-rules model account for such cases of phonological alexia? In this form of phonological alexia most words are read correctly, although functors are often reported as presenting some difficulty. The no-rules model can account for this pattern of reading performance as follows: If the direct route from lexical orthographic representations to lexical phonological representations were blocked, then all real word reading would be accomplished through the alternate lexical route. In this route access to the phonological lexicon is achieved via an orthography-to-semantics-to-phonology route within the lexicon. Since there are no semantic representations for pseudowords, there would be no means by which they could be read via this alternate route; hence, the marked deficit in reading pseudowords but near perfect reading of real words. It is also posited that function words do not have strong semantic representations; hence they may be more difficult to read via the semantic route (Glosser & Friedman, 1986; Patterson, 1982). The reading disorder known as deep alexia can also be explained by the no-rules model. Like patients with phonological alexia, patients with deep alexia cannot read pseudowords and they have particular difficulty reading functors. Within the no-rules model, this pattern suggests an impairment in the direct orthography to phonology route, as in the type of phonological alexia just described. In addition, these patients produce semantic paralexias in oral reading, they have more difficulty reading abstract than concrete words, and they display an aphasia, all of which point to a deficit in semantic processing (see Glosser & Friedman, 1986). Thus, deep alexia, by the no-rules model, reflects an impairment in the orthography to phonology route plus an impairment within the semantic system. This notion is clearly demonstrated by cases of phonological alexia that evolve from deep alexia (Glosser & Friedman, 1986). Finally, surface alexia can also be accounted for by the no-rules model. In surface alexia, pseudowords and regularly spelled real words are read
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well, while irregularly spelled words are read poorly. Comprehension of a written word is consistent with the phonological code that is assigned to the word, whether it be correct or incorrect. The no-rules model can account for this reading pattern by attributing surface alexia to a disturbance in the activation of word forms within the orthographic lexicon, which reduces the pool of candidate words from which pronunciations are derived. Normally, when a word’s orthographic word form is properly activated, the word will be pronounced and comprehended correctly whether it is a regular or irregular word. However, in the no-rules model, if a word’s orthographic word form is not properly activated, the word must be read as pseudowords are read-by analogy to whatever neighborhood words are properly activated in the orthographic lexicon (Friedman, 1988). This process would result in more correct responses for regular words, whose neighbors are indeed phonologically similar, than it would for irregular words, for which pronunciation by analogy would lead one astray. If many neighborhood words are activated, we would expect to see “regularization” errors for the irregular words. If few neighbors are activated, then substitution errors of the type that have been called “partial failure” of grapheme-phoneme rules (Marshall & Newcombe, 1973) would be expected. The no-rules model of single word reading that is supported by the reading performance of H.R. can thus account for several major forms of alexic disturbance that have been reported in the literature. This model provides for the reading of all words and pseudowords via the same method of lexical look-up, thereby obviating the need to propose a system of orthography-to-phonology “rules” that are stored separately from the lexicon. APPENDIX Examples of Errors Produced by HR Phonological
Errors
Pictures kangaroo + /kaqgalu/ pitcher + /prqktJaL/ vase 4, /vas/ Words mushroom + /brJrum/ bicycle + /brkl/ elephant --, /dabrlt/ Pseudowords mub * /mAp/ grone + /grof/ fost --* /fast/
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Errors
Pictures envelope + /amab!/ pencil -+ /til/ leaf --, /flar/ Words umbrella --f /aembrdaeb!/ zebra * /gaxaz*/ flower --f /slaxj/ Pseudowords chint --, /step/ tack - /Jrap/ grood - /stAf/ REFERENCES Beauvois, M. F., & Derouesne, J. 1979. Phonological alexia: Three dissociations. Journal of Neurology, Neurosurgery, and Psychiatry, 42, 1115-l 124. Caplan, D., Vanier, M., and Baker, C. 1986. A case study of reproduction conduction aphasia. I: Word production. Cognitive Neuropsychology, 3, 99-128. Caramazza, A., Miceli, G., & Villa, G. 1986. The role of the (output) phonological buffer in reading, writing and repetition. Cognitive Neuropsychology, 3, 37-76. Friedman, R. B. 1988. Acquired alexia. In F. Boiler & J. Grafman (Eds.), Handbook of neuropsychology. Amsterdam: Elsevier Science Publishers. Glosser, G., & Friedman, R. B., in press. The continuum of deep/phonological alexia. Cortex.
Glushko, R. J. 1979. The organization and activation of orthographic knowledge in reading aloud. Journal of Experimental Psychology, 5, 674-691. Glushko, R. J. 1981. Principles for pronouncing print: The psychology of phonology. In A. M. Lesgold and C. A. Perfetti (Eds.), Interactive processes in reading. Hillsdale, New Jersey: Lawrence Erlbaum Associates. Goldblum, M.-C. 1985. Word comprehension in surface alexia. In K. E. Patterson, J. C. Marshall, and M. Coltheart (Eds.), Surface dyslexia. London: Lawrence Erlbaum Associates. Goodglass, H., & Kaplan, E. 1983. The assessment of aphasia and related disorders. Philadelphia: Lea & Febiger. Kay, J., & Lesser, R. 1985. The nature of the phonological processing in oral reading: Evidence from surface dyslexia. Quarterly Journal of Experimental Psychology A, 37, 39-81. Kay, J., & Marcel, A. J. 1981. One process, not two, in reading aloud: Lexical analogies do the work of non-lexical rules. Quarterly Journal of Experimenral Psychology A, 33, 397-413. Kay, J., & Patterson, K. E. 1985. Routes to meaning in surface dyslexia. In K. E. Patterson, J. C. Marshall, and M. Coltheart (Eds.), Surface Dyslexia. London: Lawrence Erlbaum Associates. Kohn, S. E. 1985. Phonological breakdown in aphasia. Ph.D. thesis. Tufts University, Medford, MA. Kohn, S. E. 1989. The nature of the phonemic string deficit in conduction aphasia. Aphasioiogy
3, 209-239.
Kohn, S. E., Schonle, P. W., & Hawkins, W. J. 1984. Identification of pictured homonyms: Latent phonological knowledge in Broca’s aphasia. Brain and Language, 22, 160-166.
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Kremin, H. 1985. Routes and strategies in surface dyslexia and dysgraphia. In K. E. Patterson, J. C. Marshall, and M. Coltheart (Eds.), Surface dyslexia. London: Lawrence Erlbaum Associates. Margolin, D. I., Marcel, A. J., & Carlson, N. R. 1985. Common mechanisms in dysnomia and post-semantic surface dyslexia: Processing deficits and selective attention. In K. E. Patterson, J. C. Marshall, and M. Coltheart (Eds.), Surface dyslexia. London: Lawrence Erlbaum Associates. Marshall, J. C., & Newcombe, F. 1973. Patterns of paralexias: A psycholinguistic approach. Journal of Psycholinguistic Research, 2, 175-199. Miller, D., & Ellis, A. W. 1987. Speech and writing errors in ‘neologistic jargonaphasia’: A lexical activation hypothesis. In M. Coltheart, G. Sartori, and R. Job (Eds.), The cognitive neuropsychology of langunge. London: Lawrence Erlbaum Associates. Paivio, A., Yuille, J. C., & Madigan, S. A. 1%8. Concreteness, imagery, and meaningfulness values for 925 nouns. Journal of Experimental Psychology, Monograph Suppl. 76(l), Part 1, l-25. Patterson, K. E. 1982. The relation between reading and phonological coding: Further neuropsychological observations. In A. W. Ellis (Ed.), Normality and pathology in cognitive functions. London: Academic Press. Patterson, K. E., Marshall, J. C., & Coltheart, M. (Eds.) 1985. Surface dyslexia. London: Lawrence Erlbaum Associates. Patterson, K. E., & Shewell, C. 1987. Speak and spell: Dissociations and word-class effects. neuropsychology of In M. Coltheart, G. Sartori, and R. Job (Eds.), Th e cognitive language. London: Lawrence Erlbaum Associates.
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impaired Activation of the Phonological Lexicon: Effects upon Oral Reading RHONDA B. FRIEDMAN Aphasia Research Center, Department of Neurology, Boston University School of Medicine; and Cognitive Neuroscience Unit, Medical Neurology Branch, NIH/NINDS AND SUSAN E. KOHN Neurolinguistics Laboratory, Institute of Health Professions, Massachusetts General Hospital, and Department of Neurology, Harvard Medical School The role of the phonological lexicon in oral reading is examined in a patient with a small focal left hemisphere lesion. Impaired access to the patient’s phonological lexicon is suggested by a number of findings, including the production of phonemic errors across a variety of tasks; increasing difficulty in word production with increasing word length; and difficulty on tests of homophone and rhyme judgments. Two competing models of reading are tested: the nonlexical (“rules”) and the lexical (“no-rules”) mbdels. The rules model predicts that a disturbance in the phonological lexicon will result in surface alexia; the no-rules model predicts phonological alexia. Results indicate that the patient’s reading is most similar to phonological alexia, providing support for the no-rules model. The applicability of the no-rules model to other forms of acquired alexia is explored. 0 1990 Academic Press. Inc.
The phonological lexicon is a standard feature of current models of language processing (e.g., Caramazza, Miceii, & Villa, 1986; Patterson & Shewell, 1987). Every word (or morpheme) in a person’s vocabulary is stored in this lexicon in the form of a phonological representation, consisting of information about its syllabic structure and phonemic content (Caplan, Vanier, & Baker, 1986; Kohn, 1985). This lexicon is said to be used in oral reading, spontaneous speech, naming (Margolin, MarThis work was supported in part by USPHS Grant NSO6209. Reprint requests should be addressed to Dr. Rhonda B. Friedman, Cognitive Neuroscience Unit, NIH/NINDS, Bldg. 10 Rm. 5C-422, Bethesda, MD 20892. 278 0093-934x&O $3.00 Copyright All rights
0 1990 by Academic Press. Inc of reproduction in any form reserved.
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ccl, & Carlson, 1985), and repetition (Caplan et al., 1986; Kay & Patterson, 1985). It follows that impaired access to the phonological representations in the lexicon should affect all of these language activities, resulting in qualitatively similar errors across these activities. Errors would be expected to occur along the parameters encoded in these representations. In particular, phonemic paraphasias should be produced in all such contexts, and there should be an effect of word length such that the number of errors increases as the number of syllables in words increases (e.g., Caplan et al., 1986). Further characterization of the quality of oral reading following impairment to the phonological lexicon depends upon the type of reading model consulted. According to one popular model, depicted in Fig. 1, the pronunciation of a written word may be obtained by consulting the lexicon, or it may be obtained nonlexically, through the use of a system of orthography-to-phonology conversion rules (e.g., Caramazza et al., 1986; Patterson and Shewell, 1987). Impaired access to the phonological lexicon would force reliance upon the nonlexical reading route, and the quality of the resultant reading would depend upon the characteristics of this nonlexical pathway. Since this route is rule-driven, we would expect oral reading errors on words whose pronunciations do not follow the rules of orthography-to-phonology conversion (i.e., irregular words). The types of reading errors that we should see are errors that are the result of a rule-guided strategy, i.e., “regularization” errors. For exwritten word I I c--
i
---------
letter identification
grapheme to phoneme convysion I I I
i
L,,--,,+ FIG.
spoken word
1. The “rules”
model of single word reading.
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ample, when applying the long-vowel-silent-e rule to the irregular word come, the result is “comb.” This pattern of reading, in which irregular words are read incorrectly while regular words are read correctly, and where regularization errors are produced, is called “surface alexia” (e.g., Kay & Lesser, 1985). A corollary feature of surface alexia is good performance on reading orthographically legal pseudowords such as hote. In addition, frequency should not be a factor in the pure form of this alexia, at least for regular words, since the orthography-to-phonology rules apply to words of any frequency, including zero frequency (i.e., pseudowords). Thus, according to Model 1, which we shall call the “rules” model, a patient with damaged access to the phonological lexicon should show a reading profile consistent with surface alexia (cf. Margolin et al., 1985). Reading of nonwords and regular real words should be relatively preserved; reading of irregular real words should be poor, and should result in regularization errors. Word frequency effects should not be found. According to the reading model depicted in Fig. 2, quite a different picture would be expected with impaired access to the phonological lexicon. This model does not include a nonlexical reading route. The reading of all words-and pseudowords-utilizes the phonological entries stored in the lexicon. When a letter string is viewed, the corresponding entry in the orthographic lexicon is aroused. In addition, orthographically similar “neighborhood” entries are aroused. The entry that is an exact match with the stimulus receives maximal activation; neighborhood written word I i letter identification
spoken word FIG.
2.
The “no-rules”
model of single word reading.
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words receive only partial activation. If there is no exact match in the orthographic lexicon-either because the subject is unfamiliar with the word or because it is, in fact, a pseudoword-then no one orthographic entry receives maximal activation. A pronunciation is derived from the partially activated neighborhood words, in a process of “analogy” (Glushko, 1979, 1981; Kay & Marcel, 1981), although the exact procedures by which this occurs are unclear. For example, the pseudoword bin might activate the real words him, hit, pin, and sin. These partially activated words combine to yield the composite pronunciation “hin.” If this “no-rules” model is correct, then what pattern of oral reading would we expect if the phonological lexicon were not activated properly? Recall that in this model, the reading of all words-real regular words, real irregular words, and pseudowords-depends upon proper activation of the phonological lexicon; no alternate pathway exists. Impaired access to the phonological lexicon, then, would affect the reading of both pseudowords and real words. Irregular words should present no particular difficulty relative to regular words. Frequency effects would be likely, since all reading is still occurring through the phonological lexicon: It is likely that high frequency words have stronger representations (or higher resting levels of activation (Miller & Ellis, 1987)), and hence are less likely to be affected when the system is damaged than are low-frequency, more weakly represented words. More specific effects of impaired access to the phonological lexicon in Model 2 can be illustrated by considering the consequences of reduced probabilities of activating lexical entries. Pseudoword reading depends upon the correct activation of all neighborhood words. If any neighborhood words are not properly activated, pseudoword pronunciation will be affected. By contrast, real words do not require that all neighborhood words be activated, so long as the specific target word receives maximal activation. Let us suppose that a processing deficit has reduced the probability of correctly activating a phonological code to .X. Now any given real word has the probability .X of becoming fully activated. Pseudowords, however, depend upon the combined activation of N neighborhood words. The probability that all of those words will be activated correctly is .X to the Nth power, a probability that is lower than .X, and gets lower as the number of needed neighborhood words, N, increases. Thus, according to the “no-rules” model, when activation of the phonological lexicon is impaired we expect to see a decrement in the reading of real words, and a substantially greater decrement in the reading of pseudowords. This pattern most closely resembles “phonological alexia. ” Thus, the “rules” model and the “no-rules” model yield very different predictions about the expected pattern of reading following impaired activation of the phonological lexicon. The first model predicts surface
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alexia; the second model predicts phonological alexia. To test these two models, we present the case of a patient for whom access to the phonological lexicon is impaired following neurological damage, as evidenced by similar deficits in oral reading, picture naming, and repetition. His oral reading performance was examined with respect to those variables that differentiate surface and phonological alexia, i.e., effects of regularity, production of regularization errors, pseudoword reading ability, and effects of word frequency and word length. HISTORY H.R. is a 52-year-old right-handed attorney who suffered a left cerebrovascular accident subsequent to a myocardial infarction. He initially presented with right-sided weakness and difficulty speaking. No further details about his acute condition are available. At the time of experimental testing, a mild right hemiparesis was present. H.R. returned to work as an attorney part time, and continued to receive speech therapy. A CT scan 1 month post-onset revealed a patchy lesion involving the temporal isthmus, the posterior half of Wernicke’s area, and the posterior supramarginal and angular gyri . A language examination 1 year post-onset indicated that H.R.‘s speech was fluent and well articulated. He had moderate word-finding difficulties, and he produced phonemic paraphasias which were often self-corrected. Auditory comprehension was very good. Repetition and naming were poor. Writing and oral reading were quite impaired; however, H.R.‘s reading comprehension on the Boston Diagnostic Aphasia Exam (BDAE) (Goodglass & Kaplan, 1983) was consistently good. Furthermore, he frequently provided excellent definitions for words that he could not read aloud. To further test his comprehension of single words, we constructed 36 pairs of visually similar low frequency words. For each pair, we read aloud the definition of one of the words. H.R.‘s task was to point to the written word corresponding to the spoken definition. He scored 33/36 on this task. At three years post-onset, H.R.‘s aphasia profile remained unchanged, except for some improvement in word-finding ability (Table 1). TESTS OF THE INTEGRITY
OF THE PHONOLOGICAL
LEXICON
The following tests involve accessing the phonological lexicon from different input routes. The results of these tests provide evidence for the proposition that H.R.‘s language difficulties are best attributed to a breakdown in accessing the phonological lexicon. Single Word Production As noted earlier, it is expected that disrupted access to information within the phonological lexicon should have a similar effect upon per-
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TABLE 1 BDAE SCORES (PERCENTILES) Years post-onset
Subtest Responsive Naming Confrontation Naming Animal Naming Repetition, words Repetition, high-probability Repetition, low-probability
sentences sentences
1
3
60 45 60
75 68 70
30 20 50
40 50 50
Auditory comprehension, ideational material
complex
90
Reading comprehension, and paragraphs
sentences
95
formance on all tests of single-word oral production, and in ways that can be characterized in terms of phonological properties of the target words. In order to examine H.R.‘s ability to access stored phonological representations for oral production along different routes into the phonological lexicon, his oral production of single words was tested in the following paradigms: (1) picture naming, which involves access to the phonological lexicon via the semantic lexicon, (2) oral reading, which involves access to the phonological lexicon via the orthographic lexicon, and (3) repetition, which can involve access to the phonological lexicon via acoustic phonetic input. All responses were tape recorded and transcribed for accurate error analysis. Unless otherwise noted, tests were administered at 1.5 to 2.5 years post-onset. Picture naming vs. oral reading. To compare H.R.‘s ability to produce the name of a word from a written stimulus and from a pictured stimulus, we constructed a list of 52 picturable nouns, varying in length from one to four syllables. The list was divided into two 26-item lists. On 1 day, H.R. was asked to name the pictures corresponding to one list of nouns, and to read the words corresponding to the other list of nouns. Two weeks later he was asked to name the pictures corresponding to the second list and to read the words corresponding to the first list. The results are presented in Fig. 3. On both tests, H.R. had more difficulty in correctly producing the target words as they increased in number of syllables. (There were no statistical differences between the two tasks.) On both tests, incorrect attempts were typically phonologically related to their targets. A phonologically related attempt was defined as a re-
FRIEDMAN
AND KOHN
n 1 syllable q 2 syllable 3 syllable
q
word
reading
picture
4 syllable
naming
Task FIG.
3. Word reading versus picture naming, by number of syllables.
sponse that matched its target word in terms of at least a consonant cluster (e.g., sled ---, “slight”), a stressed vowel (e.g., kangaroo ---, “goo”), or the onset and coda of a syllable (e.g., envelope + “lop”) (Kohn, 1985). The tendency to produce phonologically related (incorrect) responses was quantified as the proportion of incorrect trials that involved at least one phonologically related response. In the picture naming condition, 75% (21/28) of H.R.‘s incorrect trials involved such phonological errors. In the reading condition, 87% (20/23) of his incorrect trials involved phonological errors. (See appendix for more examples of errors that are classified as phonological as well as some nonphonological errors.) Repetition vs. oral reading. To compare H.R.‘s ability to produce the name of a word from a written and a spoken stimulus, we constructed a separate list of 28 picturable nouns ranging in length from one to three syllables. Results are presented in Fig. 4. As with the previous production data, there is an effect of number of syllables for both conditions. The overall level of performance for repetition and reading trials is quite similar (repetition, 68%; reading, 71%). In order to obtain a large enough corpus of incorrect responses to examine H.R.‘s pattern of errors during repetition, a separate set of 40 concrete nouns ranging in length from one to three syllables was presented. Performance on this test resembled performance on the previous repetition test. He correctly repeated 75% of the target words and had more difficulty as target words increased in number of syllables (one syllable, 95%; two syllables, 86%; three syllables, 43%). All (100%) of
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n q 0
1 syllable
2 syllable 3 syllable
0 repetition
reading
Task FIG. 4. Repetition versus reading, by number of syllables.
his incorrect responses involved a phonologically related attempt (as defined above). Summary. Across the three conditions of single-word oral production, H.R.‘s performance was quite similar in terms of the strong tendency for errors to involve phonological distortions of the target word and for such errors to increase as words increased in length. The results clearly demonstrate that H.R. has a general phonological deficit that impairs his oral production under various conditions. Moreover, these results are consistent with the notion that the deficit responsible for H.R.‘s wordproduction difficulty involves access to the phonological lexicon. Reading
Errors that Reject
Activation
of Multiple
Representations
A rather dramatic demonstration of the failure to activate the precise phonological code for a word occurred on trials in which H.R., unable to provide a correct pronunciation for a written word, gave a definition instead. On occasion, H.R. would produce multiple definitions for polysemous words. For example, he gave four different (correct) definitions of the word mercury. Of particular interest were those trials in which he gave two definitions for a written word-one of which was not correct. For example, sky, which was not read aloud correctly, elicited the following definitions: “That thing up there with the clouds” and “Sometimes you get one under your eye”. Apparently, both sky and sty had become activated in the orthographic lexicon, and the appropriate semantic representations for each word had subsequently been activated. H.R. was unable to access the lexical phonological information needed to tell him that sky and sty are different words; presumably, he assumed
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that he was presented with another of the many polysemous words of English. Similar confusions were made by H.R. between slate/state, galley/gallery, and continent/countenance. We believe that such multiple activations occasionally occur among normal readers as well, but the activation of two disparate phonological codes alerts the normal reader to the likelihood that this is not correct.’ Tests of Homophone
and Rhyme Judgement
The following tests of homophone and rhyme judgement were administered in order to assess H.R.‘s ability to access phonological representations within the lexicon without the confounds of a possible output problem (cf. Kohn, Schonle, & Hawkins, 1984). In order to determine if two written words are rhymes or homophones (especially if irregular spelling is involved), the reader must first access the stored orthographic representations and then their corresponding phonological representations to determine if the two phonological representations match (i.e., correspond to similar patterns of activation in the phonological lexicon). Similarly, in order to determine whether the names of two pictures are rhymes or homophones, the stored phonological representations of the pictures’ names must be compared. These tests do not require such components of phonological production as phonemic string construction or a phonemic output buffer for accurate performance (cf. Kohn, 1989). Trials for the tests of homophone and rhyme judgements were presented to H.R. individually on index cards. Homophone matching. H.R. was asked to identify written homophones under several different conditions. To determine the extent to which H.R. could identify homophones using lexical representations (as opposed to grapheme-phoneme conversion rules), he was given a test where many of the words contained spellings with ambiguous pronunciations. Specifically, he was asked to decide whether two written words were homophones, where positive and negative pairs were matched for visual similarity (e.g., doe-dough; toe-tough). On this 84-item test, there was an equal number of pairs with one- and two-syllable words. H.R. was correct on 74% of the trials (80% on homophone pairs; 61% on nonhomophone pairs). In another task, H.R. had to match a written word to its corresponding homophone from among four written choices. All written words were ’ As one reviewer pointed out, it is possible that normal readers never arouse incorrect orthographic lexical entries, and that these errors produced by H.R. reflect an impairment of the orthographic lexicon itself. While this is possible, the small number of words that were missed in this fashion suggest to us that H.R. does not have such a deficit. In any case, the fact remains that H.R. cannot disambiguate the words using phonological information.
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single syllable and ranged from three to five letters. Foils were rhymes and alliterations (e.g., sail: mail, salt, said, sale). He scored 86% correct. Finally, H.R. was given a more difficult four-choice test of homophone matching. In this test not every trial contained a homophone among the choices. In this way, we could be sure that he was searching for complete phonological identity between words, and not simply the closest phonological match. H.R. was instructed to make sure that the word chosen was not only the best choice, but a perfect match. If no match appeared among the choices, he was instructed to say so. This test had 30 trials, 10 of which contained no homophones. As with the previous multiplechoice test, all words were single syllable with three to five letters, and foils were rhymes and alliterations. H.R. scored 73% correct. Rhyming. As with the homophone judgements, H.R.‘s ability to detect rhymes was assessed in several ways. However, before these tests were administered, we determined that he understood the concept of a rhyme in the following manner. H.R. was given a spoken word, followed by three spoken words that rhyme with the target word. After each of these words was spoken, he was told that the word rhymes with the initial target word. He was then presented with 11 spoken words. After each word, he was asked if that word rhymed with the target word. This procedure was repeated for a second target word. H.R.‘s yes-no decision was correct for all 22 items, 10 yes’s and I2 no’s H.R. was next presented with pairs of written words and asked to determine whether each pair rhymed. There were 50 pairs of visually similar words. Half of the pairs were rhymes (past-cast), while the remaining nonrhyme pairs were constructed so that they were analogous to the rhyming pairs (paste-caste). Thus, as with the homophone test involving word pairs, many words involved ambiguous spellings. H.R. was successful on 70% of the trials (20/25 rhymes; 15/25 nonrhymes). This level of performance indicates that he can do the task, but that on a large number of trials he does not have sufficient phonological information about the two words to make the correct choice. H.R. was given one other test of rhyme judgement that was more difficult insofar as it increased processing demands within the phonological lexicon. A multiple choice task was employed to examine H.R.‘s ability to determine whether the names of various pictures rhyme with one another. On each of 15 trials there was a target picture, and three choice pictures. The names of each of the three choice pictures began with the same letter and differed either in the vowel or in the final consonant (e.g., CAN pin pan pail). All stimulus names were single syllable. H.R.‘s task was to choose the picture whose name rhymes with the name of the target picture. He scored 6/15, which is not above chance on this task. Summary. H.R.‘s performance on tests of homophone and rhyme
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judgements matched the expectations for impaired access to the phonological lexicon. Insofar as such tests involve the evaluation of stored phonological representations, his impaired performance on such tests can be interpreted as evidence for impaired lexical phonological access. TESTS OF SINGLE WORD ORAL READING The following tests of reading are typically used when assessing acquired disorders of reading, in order to fully characterize the type of reading impairment present: tests of the effects of regularity, part of speech, concreteness, frequency, and word length; tests of pseudoword reading; and examination of the types of errors produced. Of particular interest here are those that distinguish between surface and phonological alexia. Specifically, patients with surface alexia should read pseudowords well, should show an effect of regularity, and should produce regularization errors. Patients with phonological alexia should read pseudowords poorly, show no effect of regularity, and produce no regularization errors. Unless stated otherwise, the tests reported in this section were administered approximately 1.5 years post-onset. Pseudowords H.R. was asked to read 180 one-syllable pseudowords (PWs). He read only 7% correctly. Similar to his errors on real word reading, 82% of the errors he produced on PW reading bore phonological resemblance to the target pseudowords (e.g., hocks + /blap/; cheef + /tJit/). (The definition of phonological similarity that we used can be found in the discussion of picture naming, above.) Regularity Twenty-five regular words (e.g., chess) and 25 irregular words (e.g., chef) were presented to H,.R. for oral reading. He read 14 of the regular words, and 17 of the irregular words. Eighteen months later, H.R. was asked to read a new list of 20 regular and 20 exception words. Half of the words in each list were high frequency; half were low frequency. The results, presented in Fig. 5, show no effects of regularity, but a striking effect of frequency. Regularization Errors In examining for paralexic responses that could be classified as “regularization errors”, i.e., errors that appear to be the result of correctly applying spelling-to-sound correspondence rules in the wrong context, we attempted to use as large a pool of oral reading responses as possible. Consequently we pooled together the responses produced on many oral reading tests, spanning many months. Of the 622 paralexic errors that were found in this pool of words, only 1% could be considered regu-
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Q
high frequency
+
low frequency
.> regular
irregular
Regularity FIG. 5. Word reading: Effects of regularity versus frequency.
larization errors. Note that all of these errors (e.g., LOOSE -+ “news”; put + “putt”; plan --, “plane”) could very well be considered phonological errors as well. (Compare with these phonological errors, which cannot be considered regularizations: butter-y -+ /bct&le/, snowman + /snuman/.) Part of Speech An oral reading test containing equal numbers of concrete nouns, abstract nouns, adjectives, verbs, and three kinds of functors failed to demonstrate any effect of part of speech. In a separate test of functor word reading, 21 pairs of functor-nonfunctor homophones (be/bee, or/oar) were presented to H.R. In this task, which fully equates phonological complexity, H.R. scored 16/21 on functors, 17/21 on nonfunctors. Eighteen months later H.R. was. asked to read 305 words of 3-8 letters. Words were matched across part of speech for number of syllables, number of letters, and whether or not the first letter of the word is a vowel. Within the constraints outlined, words were chosen to be as high in frequency as possible. H.R.‘s scores were as follows: Concrete nouns, 53; abstract nouns, 53; adjectives, 53; verbs, 54; functors, 46. Taken together, these results indicate no part of speech effects in H.R.‘s oral reading, other than a possible weak, unreliable tendency for functors to be read less efficiently than content words. Concreteness In the first test for part-of-speech effects, the nouns were divided into those that are abstract and those that are concrete. All 10 concrete nouns
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were read correctly; 7 of the 10 abstract nouns were read correctly. We pursued this factor further by administering another test of oral reading of nouns 2 months later. On this test H.R. read 11/15 concrete nouns and 7/15 abstract nouns. As before, there was a nonsignificant tendency towards reading concrete nouns better than abstract nouns (x2 = 1.25). One year later, a list of 30 concrete and 30 abstract nouns was administered. H.R. read 25/30 concrete nouns and 15/30 abstract nouns. This difference is significant (x2 = 6.075, u” = 1, p < .02). Around the same time, H.R. was asked to read M. Coltheart’s list of 28 high imageability and 28 low imageability words. Imageability is highly correlated with concreteness (Paivio, Yuille, & Madigan, 1968), and some authors believe that it is the effect of imageability, not concreteness per se, that is sometimes seen in brain-damaged patients. H.R. read 12/28 high imageability and 12/28 low imageability words. One-half year later, the 305-word parts of speech list mentioned above was given to H.R. for oral reading. As noted, H.R. successfully read 53 of the concrete and 53 of the abstract nouns. In a final attempt to determine whether or not an effect of concreteness can be seen in H.R.‘s reading, a list of 75 concrete and 75 abstract words (40 high frequency pairs; 35 low frequency pairs) was presented to H.R. for oral reading. Results can be seen in Fig. 6. While there is a large effect of frequency, no effect of concreteness can be detected. The combined results of these five tests indicate that the concreteness variable was not a reliable factor in H.R.‘s reading performance.
100
”
.
~~~
Q
high
+
low frequency
frequency
1
concrete
abskxt
Concreteness FIG.
6. Word reading: Effects of concreteness versus frequency.
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Frequency H.R. was asked to read a list of 48 words of one to three syllables, matched for length across frequency. He correctly read 6/16 high frequency, 4/16 middle frequency, and 2/16 low frequency words on the first attempt. The number of words read correctly given unlimited attempts was 1l/16,7/16, and 4/16 for the high, middle, and low frequency words, respectively. The effect of frequency on H.R.‘s oral reading remained strong 18 months later. On one test of concreteness and on a separate test of the effects of regularity H.R.‘s reading was greatly affected by frequency. (See sections on Regularity and Concreteness; Figs. 5 and 6). Word Length The first test given to H.R. for the assessment of effects of word length consisted of 40 nouns. His accuracy on words of 3, 5, 7, and 9 letters, respectively, was 78, 80. 44, and 17%. When broken down by number of syllables, the results for 1, 2, 3, and 4 syllable words were 78, 63, 15, and O%, respectively. In a second, more controlled test of word length, H.R.‘s scores on 4, 6-, and S-letter words were 100, 73, and 30%, respectively. He read 90% of the one-syllable, 67% of the two-syllable, and 50% of the three-syllable words. To take a closer look at the effects of number of letters vs. number of syllables, we looked at H.R.‘s reading of 40 nouns. There were five words in each of eight syllable X letter combinations. As can be seen in Table 2, it is the number of syllables, not the number of letters, that affects H.R.‘s performance.
TABLE PROPORTION
OF WORDS
READ NUMBER
2
CORRECTLY,
BY NUMBER
Number
Number 1 2 3 4
Nofe.
OF LETTERS
AND
OF SYLLABLES
of letters
3-4
5-6
l-8
.6 .2 0.40
.8 .4 0.0 0.40
.2 0.0 0.0 0.07
of syllables
n = 5 words
per cell.
0.70 0.27 0.00 0.00
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DISCUSSION The purpose of this case study was two-fold: (1) to demonstrate that H.R.‘s oral production and reading deficits reflect a deficit in accessing the phonological lexicon and (2) to determine which of two lexical models best accounts for this pattern of behavior. Model 1, which includes a system of nonlexical orthography-to-phonology conversion rules, predicts surface alexia following disturbed activation of the phonological lexicon. Model 2, whose only route to reading is through lexical access, predicts phonological alexia. It is clear that H.R. has a phonological deficit that affects oral production in all contexts. Across tests of oral reading, repetition, and picture naming, errors were consistently phonologically related to targets, and performance was affected by the number of syllables in the targets. This phonological deficit appears to involve impaired access to the phonological lexicon, as opposed to a postlexical output deficit. This is supported by his poor performance on tests that require access to stored phonological representations without requiring a spoken response, such as homophone and rhyme judgements. His unusual reading errors, in which activation of two phonologically similar words goes unnoticed, is further evidence that lexical phonology is not properly accessed. In tests of oral reading, we found no evidence of surface alexia. H.R. displayed a severe deficit in reading pseudowords, a milder deficit in reading real words, no regularization errors, and no effect of regularity. Thus, Model 1, the “rules” model, is not supported. Instead, this reading performance most resembles phonological alexia, supporting the prediction of Model 2, the “no-rules” model. This interpretation is based upon the assumption that we are dealing with a single functional deficit. Parsimony favors the explanation that relies on the fewest deficits to account for the data. Still, it is possible for Model 1 to account for the data by claiming that H.R. has two functional deficits, one in accessing the phonological lexicon and a more severe deficit in the “indirect” rule-driven reading route. It is of course difficult to disprove a two-deficit hypothesis for H.R. Nonetheless, if H.R. does have two separate deficits, then we should expect to see some patients who have only a deficit in accessing the phonological lexicon. Such patients, according to Model 1, should have surface alexia. Are there any such cases in the literature? The edited volume Surface Dyslexia (Patterson, Marshall, & Coltheart, 1985) provides several potential candidates. Margolin et al. (1985) present the case of R.F. whose’ oral reading and picture naming are impaired. The authors conclude that “entries in R.F.‘s phonological lexicon are of reduced accessibility” (p. 151). Does R.F. read like a surface alexic or a phonological alexic? Surface alexics, by definition, show an effect
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of regularity and read pseudowords well. In oral reading of real words R.F. does not show a significant effect of regularity, and her oral reading of pseudowords is poor. The authors argue, despite these findings, that R.F. should nevertheless be considered a surface alexic because she appears to be using a “sublexical strategy” for reading. However, by all objective criteria, R.F.‘s reading is more consistent with phonological alexia. In the same volume, Kay and Patterson (1985) present a patient, E.S.T., who had difficulties in reading, picture naming, and spontaneous speech following removal of a meningioma. The authors claim that “the primary impairment in E.S.T.‘s case is in gaining access to lexical phonology” (p. 99). Although E.S.T. produced regularization errors, his reading of irregular words was not significantly worse than regular words. He read 84% of pseudowords using an “acceptable” pronunciation: his responses were often correct by analogy but not by strict application of spelling-to-sound correspondence rules. This patient does not fit neatly into either category of surface or phonological alexia. A potential problem in interpreting this case is that effects of number of syllables were not measured-a critical variable for identifying breakdown within the phonological lexicon. Another problem is that both auditory comprehension and reading comprehension were impaired. These multiple deficits call into question the assertion that E.S.T.‘s difficulties are strictly the result of problems within the phonological lexicon. Thus this case also fails to demonstrate surface alexia that is solely caused by a disturbance in the phonological lexicon. Goldblum’s (1985) case of “postsemantic” surface alexia, in the same volume, is also attributed to a disturbance within the phonological lexicon. However, the patient showed no effect of number of syllables on word reading; picture naming that was superior to oral reading; and a difference in the quality of production errors between these two tasks. These findings suggest a word-finding impairment specific to reading, rather than a general problem with the phonological lexicon. Finally, the patient of Kremin (1985), described as a surface alexic with phonological disruption, may be a good example of surface alexia, but she does not appear to have a deficit within the phonological lexicon. She had difficulty with oral reading and picture naming and she read regular words more accurately than irregular words. Her level of pseudoword reading was relatively high, 72%. However, there was no effect of number of syllables for naming, and a questionable effect for oral word reading. In addition, her performance on a rather difficult written homophone matching test was excellent. This pattern of performance suggests that she does have relatively intact access to the phonological codes for lexical items. We have thus failed to uncover any convincing evidence that an iso-
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lated deficit in accessing the phonological lexicon can produce surface alexia. Consequently, at present we reject the less parsimonious interpretation that H.R.‘s problems are the result of two separate functional deficits and reaffirm our conviction that all of his deficits can be attributed to the disturbance of a single underlying mechanism-activation of the phonological lexicon. In describing the pattern of reading deficits displayed by H.R., we have demonstrated one way that phonological alexia might be produced within the framework of the “no-rules” model, i.e., disruption to the phonological lexicon. The question remains as to how well this model accounts for other reading disorders. For example, phonological alexia has also been reported in patients for whom activation of the phonological lexicon does not appear to be impaired (Beauvois and Derouesne, 1979). How does the no-rules model account for such cases of phonological alexia? In this form of phonological alexia most words are read correctly, although functors are often reported as presenting some difficulty. The no-rules model can account for this pattern of reading performance as follows: If the direct route from lexical orthographic representations to lexical phonological representations were blocked, then all real word reading would be accomplished through the alternate lexical route. In this route access to the phonological lexicon is achieved via an orthography-to-semantics-to-phonology route within the lexicon. Since there are no semantic representations for pseudowords, there would be no means by which they could be read via this alternate route; hence, the marked deficit in reading pseudowords but near perfect reading of real words. It is also posited that function words do not have strong semantic representations; hence they may be more difficult to read via the semantic route (Glosser & Friedman, 1986; Patterson, 1982). The reading disorder known as deep alexia can also be explained by the no-rules model. Like patients with phonological alexia, patients with deep alexia cannot read pseudowords and they have particular difficulty reading functors. Within the no-rules model, this pattern suggests an impairment in the direct orthography to phonology route, as in the type of phonological alexia just described. In addition, these patients produce semantic paralexias in oral reading, they have more difficulty reading abstract than concrete words, and they display an aphasia, all of which point to a deficit in semantic processing (see Glosser & Friedman, 1986). Thus, deep alexia, by the no-rules model, reflects an impairment in the orthography to phonology route plus an impairment within the semantic system. This notion is clearly demonstrated by cases of phonological alexia that evolve from deep alexia (Glosser & Friedman, 1986). Finally, surface alexia can also be accounted for by the no-rules model. In surface alexia, pseudowords and regularly spelled real words are read
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well, while irregularly spelled words are read poorly. Comprehension of a written word is consistent with the phonological code that is assigned to the word, whether it be correct or incorrect. The no-rules model can account for this reading pattern by attributing surface alexia to a disturbance in the activation of word forms within the orthographic lexicon, which reduces the pool of candidate words from which pronunciations are derived. Normally, when a word’s orthographic word form is properly activated, the word will be pronounced and comprehended correctly whether it is a regular or irregular word. However, in the no-rules model, if a word’s orthographic word form is not properly activated, the word must be read as pseudowords are read-by analogy to whatever neighborhood words are properly activated in the orthographic lexicon (Friedman, 1988). This process would result in more correct responses for regular words, whose neighbors are indeed phonologically similar, than it would for irregular words, for which pronunciation by analogy would lead one astray. If many neighborhood words are activated, we would expect to see “regularization” errors for the irregular words. If few neighbors are activated, then substitution errors of the type that have been called “partial failure” of grapheme-phoneme rules (Marshall & Newcombe, 1973) would be expected. The no-rules model of single word reading that is supported by the reading performance of H.R. can thus account for several major forms of alexic disturbance that have been reported in the literature. This model provides for the reading of all words and pseudowords via the same method of lexical look-up, thereby obviating the need to propose a system of orthography-to-phonology “rules” that are stored separately from the lexicon. APPENDIX Examples of Errors Produced by HR Phonological
Errors
Pictures kangaroo + /kaqgalu/ pitcher + /prqktJaL/ vase 4, /vas/ Words mushroom + /brJrum/ bicycle + /brkl/ elephant --, /dabrlt/ Pseudowords mub * /mAp/ grone + /grof/ fost --* /fast/
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Errors
Pictures envelope + /amab!/ pencil -+ /til/ leaf --, /flar/ Words umbrella --f /aembrdaeb!/ zebra * /gaxaz*/ flower --f /slaxj/ Pseudowords chint --, /step/ tack - /Jrap/ grood - /stAf/ REFERENCES Beauvois, M. F., & Derouesne, J. 1979. Phonological alexia: Three dissociations. Journal of Neurology, Neurosurgery, and Psychiatry, 42, 1115-l 124. Caplan, D., Vanier, M., and Baker, C. 1986. A case study of reproduction conduction aphasia. I: Word production. Cognitive Neuropsychology, 3, 99-128. Caramazza, A., Miceli, G., & Villa, G. 1986. The role of the (output) phonological buffer in reading, writing and repetition. Cognitive Neuropsychology, 3, 37-76. Friedman, R. B. 1988. Acquired alexia. In F. Boiler & J. Grafman (Eds.), Handbook of neuropsychology. Amsterdam: Elsevier Science Publishers. Glosser, G., & Friedman, R. B., in press. The continuum of deep/phonological alexia. Cortex.
Glushko, R. J. 1979. The organization and activation of orthographic knowledge in reading aloud. Journal of Experimental Psychology, 5, 674-691. Glushko, R. J. 1981. Principles for pronouncing print: The psychology of phonology. In A. M. Lesgold and C. A. Perfetti (Eds.), Interactive processes in reading. Hillsdale, New Jersey: Lawrence Erlbaum Associates. Goldblum, M.-C. 1985. Word comprehension in surface alexia. In K. E. Patterson, J. C. Marshall, and M. Coltheart (Eds.), Surface dyslexia. London: Lawrence Erlbaum Associates. Goodglass, H., & Kaplan, E. 1983. The assessment of aphasia and related disorders. Philadelphia: Lea & Febiger. Kay, J., & Lesser, R. 1985. The nature of the phonological processing in oral reading: Evidence from surface dyslexia. Quarterly Journal of Experimental Psychology A, 37, 39-81. Kay, J., & Marcel, A. J. 1981. One process, not two, in reading aloud: Lexical analogies do the work of non-lexical rules. Quarterly Journal of Experimenral Psychology A, 33, 397-413. Kay, J., & Patterson, K. E. 1985. Routes to meaning in surface dyslexia. In K. E. Patterson, J. C. Marshall, and M. Coltheart (Eds.), Surface Dyslexia. London: Lawrence Erlbaum Associates. Kohn, S. E. 1985. Phonological breakdown in aphasia. Ph.D. thesis. Tufts University, Medford, MA. Kohn, S. E. 1989. The nature of the phonemic string deficit in conduction aphasia. Aphasioiogy
3, 209-239.
Kohn, S. E., Schonle, P. W., & Hawkins, W. J. 1984. Identification of pictured homonyms: Latent phonological knowledge in Broca’s aphasia. Brain and Language, 22, 160-166.
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Kremin, H. 1985. Routes and strategies in surface dyslexia and dysgraphia. In K. E. Patterson, J. C. Marshall, and M. Coltheart (Eds.), Surface dyslexia. London: Lawrence Erlbaum Associates. Margolin, D. I., Marcel, A. J., & Carlson, N. R. 1985. Common mechanisms in dysnomia and post-semantic surface dyslexia: Processing deficits and selective attention. In K. E. Patterson, J. C. Marshall, and M. Coltheart (Eds.), Surface dyslexia. London: Lawrence Erlbaum Associates. Marshall, J. C., & Newcombe, F. 1973. Patterns of paralexias: A psycholinguistic approach. Journal of Psycholinguistic Research, 2, 175-199. Miller, D., & Ellis, A. W. 1987. Speech and writing errors in ‘neologistic jargonaphasia’: A lexical activation hypothesis. In M. Coltheart, G. Sartori, and R. Job (Eds.), The cognitive neuropsychology of langunge. London: Lawrence Erlbaum Associates. Paivio, A., Yuille, J. C., & Madigan, S. A. 1%8. Concreteness, imagery, and meaningfulness values for 925 nouns. Journal of Experimental Psychology, Monograph Suppl. 76(l), Part 1, l-25. Patterson, K. E. 1982. The relation between reading and phonological coding: Further neuropsychological observations. In A. W. Ellis (Ed.), Normality and pathology in cognitive functions. London: Academic Press. Patterson, K. E., Marshall, J. C., & Coltheart, M. (Eds.) 1985. Surface dyslexia. London: Lawrence Erlbaum Associates. Patterson, K. E., & Shewell, C. 1987. Speak and spell: Dissociations and word-class effects. neuropsychology of In M. Coltheart, G. Sartori, and R. Job (Eds.), Th e cognitive language. London: Lawrence Erlbaum Associates.