Mechanisms for accessing lexical representations for output: Evidence from a category-specific...

BRAIN AND LANGUAGE 4, 106-144 (1991)

Mechanisms for Accessing Lexical Representations for Output: Evidence from a Category-Specific

Semantic Deficit

ARGYE E. HILLIS

HealthSouth Rehabilitation Corporation

AND

ALFONSO CARAMAZZA

Department of Cognitive Science, The Johns Hopkins University

We report the performance of a neurologically impaired patient, JJ, whose oral reading of words exceeded his naming and comprehension performance for the same words-a pattern of performance that has been previously presented as evidence for “direct, nonsemantic, lexical” routes to output in reading. However, detailed analyses of JJ’s reading and comprehension revealed two results that do not follow directly from the “direct route” hypothesis: (1) He accurately read aloud all orthophonologically regular words and just those irregular words for which he demonstrated some comprehension (as indicated by correct responses or within-category semantic errors in naming and comprehension tasks); and (2) his reading errors on words that were not comprehended at all (but were recognized as words) were phonologically plausible (e.g., soot read as “suit”). We account for these results by proposing that preserved sublexical mechanisms for converting print to sound, together with partially preserved semantic information, serve to mediate the activation of representations in the phonological output lexicon in the task of reading aloud. We present similar arguments for postulating an interaction between sublexical mechanisms and lexical output components of the spelling process. D 1991 Academic Pres,. Inc.

The research reported here was supported in part by NIH Grant NS22201 and by grants from the Seaver Institute and the McDonnell/Pew Program in Cognitive Neuroscience. This support is acknowledged with gratitude. We also thank Chris Barry and an anonymous referee for detailed and helpful comments on an earlier version of this paper, and we are particularly grateful to JJ for his cheerful participation in the studies. Address reprint requests to Alfonso Caramazza, Department of Cognitive Science, The Johns Hopkins University, Baltimore, MD 21218.

0093-934)(/91 $3.00 Copyright 0 1991 by Academic Press, Inc. All rights of reproduction in any form reserved.

106

ACCESSING LEXICAL REPRESENTATIONS 107

Semantic System

Orthographic 1 Output Lexicon

Spoken Output Written Output FIG. 1. Schematic representation of the major components of lexical processing.

Recent research in aphasia has provided evidence that the lexical system-the cognitive processes which underlie tasks such as spelling, naming, and comprehension of words--consists of relatively independent processing components which can be selectively impaired by brain damage. One hypothesis about the structure of the lexical processing system is that it consists of a set of modality-specific input and output components in- terconnected by a semantic component (see Fig. 1). Damage to different components of the lexical system results in distinct patterns of performance, each pattern reflecting the joint operation of the damaged and spared components. For example, selective impairment in accessing the phonological representations of familiar words, due to damage at the level of the Phonological Output Lexicon, should result in impaired ability to produce orally the names of pictures, but spared ability to write the names

108 HILLIS AND CARAMAZZA

of the same pictures (see Caramazza & Hillis (1990); Ellis, Miller, & Sin (1983); Hier & Mohr (1977); and Levine, Calvanio, & Popovics (1982) for such cases). A different pattern of performance is expected in cases where the semantic component is impaired. In this case, the patient should have difficulty in both written and oral naming of objects, as well as in comprehension of the names of the same objects. This type of damage should also disrupt oral reading, spelling to dictation, and repetition, unless these tasks can be performed by engaging alternative mechanisms (see Hillis, Rapp, Romani, & Caramazza (1990) for such a case). So, for example, a semantic deficit would not impede repetition of words if the patient is able to mimic sounds of the word without retrieving the stored, lexical-phonological representation.

Other patterns of impaired lexical processing have established that brain damage can selectively impair certain categories of words at different levels of the lexical system. Thus, there are various reports that document differential impairment of low- versus high-frequency words (see papers in Patterson, Marshall, & Coltheart (1985); words of different grammatical classes, nouns versus verbs, or closed versus open class words (see papers in Coltheart, Patterson, & Marshall (1980)); and words of different semantic categories (see Hart, Berndt, & Caramazza (1985); Warrington & McCarthy (1983, 1987); Warrington & Shallice (1984) for examples; see Berndt (1988) and Shallice (1988) for reviews). Among the latter cases, there have been several reports of impaired comprehension and naming restricted to the category of animals (Sartori & Job, 1988; Silveri & Gainotti, 1988; Hart & Gordon, 1988). Complementing these results, we have recently described a patient, JJ, who showed relatively preserved naming and comprehension restricted to the category of animals, along with a patient, PS, who showed the opposite pattern of performance with the same stimuli (Hillis & Caramazza, in press, a). That is, JJ’s oral and written naming and his comprehension of written and spoken words (tested by word/picture verification and by definition of spoken words tasks) were severely impaired for all categories of words tested (including verbs, adjectives, abstract nouns, and concrete nouns in categories of fruits, body parts, clothing, and flowers) other than animals, whereas PS’s picture naming and word comprehension were markedly impaired only in the categories of animals and vegetables. For these two patients, the category effects persisted even as they recovered language skills. We interpreted the double dissociation between categories in naming and comprehension of animal words as resulting from selective impairment or sparing within the semantic system.

There was, however, one major difficulty for the proposal that the category effect recorded for JJ resulted from selective impairment to the semantic system: His performance was not equivalent across all tasks that


are assumed to involve the semantic system.’ His performance in oral reading surpassed his performance in oral naming, such that all categories of words (including some irregular words) were accurate in oral reading and in spelling to dictation, despite persisting category-specific oral and written naming deficits. These results are problematic because, excluding other factors, category effects that arise at a specific level of processing should appear in all tasks that involve that processing component and should not appear in tasks that do not. In cases of damage to the semantic system, we would argue that the tasks that normally require the damaged component include reading and spelling, as well as naming and comprehension (see Fig. 1). (This claim is obvious if we consider oral reading of heterophonic homographs like tear and spelling of heterographic homophones like /tir/ (tear and tier), which require accurate semantic processing in order to select the contextually accurate pronunciation or spelling.) However, as already noted, performance of a task may be accomplished through the application of different processing procedures- for example, some lexical tasks, such as repetition, can be accomplished by sublexical procedures used in processing nonwords or unfamiliar words, as well as by activating the meaning of the word and then the corresponding lexical-phonological representation. So, the results reported for JJ would be consistent with the hypothesis of selective impairment of semantics if it could be assumed (as is often done) that oral reading can be successful without access to semantic information. At least two types of processing procedures for reading without access to semantic information have been proposed: (1) by the application of sublexical orthography-to-phonology conversion (hereafter, OPC) procedures for assem- bling a pronunciation from print (Coltheart, 1978); and (2) by the application of procedures for accessing entries in the Phonological Output Lexicon directly from the Orthographic Input Lexicon (Bub, Cancelliere, & Kertesz, 1985; Funnell, 1983; McCarthy & Warrington, 1986; Schwartz, Saffran, & Marin, 1980; Sartori, Masterson & Job, 1987; Shallice, 1988). In order to maintain the hypothesis that JJ’s semantic errors result from damage at the level of the semantic system, we would have to postulate that one or both of these nonsemantic procedures for pronunciation could support JJ’s oral reading performance. Furthermore, to explain his level of accuracy in writing to dictation, we would also have to assume that sublexical phonology-to-orthography conversion (POC) procedures and/or nonsemantic lexical access to orthographic representations is intact.

I PS also showed disproportionately better oral reading and spelling to dictation than naming in categories that were impaired; however, this paper focuses on JJ’s performance, because more extensive testing was completed with him.


The first type of nonsemantic processing procedure, OPC and POC procedures for converting print to sound and sound to print, respectively, are components of the “dual-route” models of the reading and spelling systems, in which there are relatively independent mechanisms for assem- bling phonological and orthographic output representations. In this view, we would expect to find patients without damage to sublexical transcoding mechanisms (but with semantic impairments) who make many errors in oral naming, but few errors in oral reading. These patients should have trouble reading only those items that are both orthophonologically “irregular” and affected by the lexical deficit. In fact, many such patients have been described (see, for example, Coltheart, Masterson, Byng, Prior, & Riddoch (1983) and papers in Patterson et al. (1985)). In such cases, performance can be explained by assuming: (1) impaired access to information in the Phonological Output Lexicon and (2) unimpaired application of sublexical mechanisms to read correctly “regular” words, as indicated by accuracy greater for regular than for irregular words and by phonologically plausible responses to irregular words.

However, there have been reports of patients who are able to read many orthophonologically irregular words fluently and accurately, despite very impaired comprehension (indicated by failure to reach functional levels on printed word/picture matching tests). Because oral reading of irregular words cannot be accomplished on the basis of OPC mechanisms and apparently is not founded on intact information from the semantic system, their oral reading has been explained by proposing nonsemantic, lexical mechanisms-direct activation of lexical-phonological representations from lexical-orthographic information (e.g., Bub et al. (1985); Schwartz et al (1980)).

Similarly, nonsemantic, lexical procedures have been proposed in the functional architectures of the spelling system (Baxter & Warrington, 1987; Goodman & Caramazza, 1986a; Kremin, 1987; Patterson, 1986). The argument in favor of nonsemantic, lexical spelling systems has taken one of the following forms: (1) the patient is able to spell at least some irregular words, despite substantial deficits in the semantic system (Good- man-Schulman, 1988; Roeltgen, Gonzalez-Rothi, & Heilman, 1986); (2) the patient correctly spells some words despite impaired semantic information and impaired POC mechanisms (Kremin, 1987); (3) the patient is able to write to dictation words, including some irregular words that he understands, in the face of an inability to write the same words in a written naming task (interpreted as evidence for proposing a “discon- nection” between the semantic system and the orthographic output lexicon; Patterson (1986))) or (4) the patient substitutes irregular homophones for target words (e.g., one for won), despite intact comprehension of the stimuli (Goodman & Caramazza, 1986a). In each case, it is argued that the patient’s responses could not have resulted either from access to


the orthographic representations from the semantic system or from as- sembly of the responses via the POC mechanisms, so the responses must have resulted from access to the Orthographic Output Lexicon directly from the Phonological Input Lexicon.’

JJ also showed the type of response pattern that has provided the primary impetus for proposing “direct routes” from input to output lexicons-he read aloud narrative material fluently with very few errors, despite very impaired comprehension of what he was reading, and he correctly spelled words that he did not fully understand. His reliance on sublexical procedures was indicated by excellent performance in reading and spelling nonwords and by some phonologically plausible errors in both oral reading (e.g., pear + “peer”) and spelling (e.g., “beet” + beate). However, he was also able to read and spell some nonanimal names that have irregular spelling, despite making semantic errors in response to the same items in comprehension tasks.

The dissociation between naming and comprehension on the one hand and oral reading and spelling on the other would, at least on the surface, seem to favor the hypothesis that JJ had damage to the semantic system, affecting all categories of words but animals, but preserved ability to use the direct lexical routes for word production. However, there is an alternative account of the observed results that does not require that we postulate direct connections between input and output lexicons. In this paper we consider whether this alternative proposal can account for performance by JJ and other patients who read aloud or spell irregular words that they do not understand perfectly.

The alternative account we offer consists of a set of related hypotheses about the organization and processing structure of the reading and spelling systems. Our first hypothesis concerns the nature of the representations that are computed in these two tasks, focusing, in particular, on reading. For the present purposes, a central assumption is that semantic representations consist of sets of functional, perceptual, and other “defining” features of the represented item. For example, the semantic representation of (GIRL) might consist of semantic features such as (FEMALE, YOUNG, HUMAN,. . .). Furthermore, we assume that each semantic

’ An alternative version of the “third route” of spelling, put forward by Patterson (1986), among others, is that correct responses in writing to dictation can result from access to the Phonological Output Lexicon from the Phonological Input Lexicon and then access from the Phonological Output Lexicon to the Orthographic Output Lexicon. Patterson noted that although she preferred this account, whereby “communication from the auditory input lexicon to the orthographic output lexicon is mediated by the phonological output lexicon” (p. 354) over the more direct route hypothesis to account for performance of her patient, there is little if any evidence for distinguishing between the two accounts. Therefore, when we refer to the “direct” or nonsemantic lexical route for spelling, we do not distinguish between the mediated and unmediated versions; our arguments apply equally to both.


feature activates, to some degree, all the representations in the output lexicon corresponding to items whose meaning contains that feature. To illustrate this assumption in the context of reading, the semantic feature (FEMALE) would partly activate phonological representations of “girl,” “woman,” “ewe,” “doe,” etc., while (YOUNG) would activate “girl,” “boy, ” “lamb,” “fawn,” “sapling,” and the like. Of the activated lexical- phonological representations, the one that received the greatest degree, or some “threshold” level, of activation would become available for further processing. In our example, the phonological representation for “girl” would be maximally activated by all the semantic features of the representation of (GIRL), but related entries in the phonological output lexicon, like “woman” and “boy,” would also be activated to some extent. Thus, if as a consequence of brain damage, normal processing of a particular lexical representation were impeded, other more available (semantically related) lexical entries could receive sufficient activation to reach threshold for output (see Caramazza & Hillis (1990) for this type of account of semantic paraphasias in the presence of spared comprehension). In summary, the proposal we are outlining here assumes that semantic representations activate in parallel all semantically related lexical representations in proportion to the degree of relatedness to the target representation. Under normal conditions, this leads to the production of the correct response-the lexical item with the greatest degree of activation. Under conditions of brain damage, no lexical representation may receive optimal activation, resulting in the default production of the most readily accessible representation-the most frequent item from the set of activated representations.

The other major assumption for the account we propose is that lexical- phonological representations can be activated not only by semantic information, but also by sublexical-phonological information generated by OPC procedures. More specifically, the string of phonemes generated by OPC procedures from the input orthographic representation activates entries in the Phonological Output Lexicon to an extent proportional to their degree of phonological similarity with the input string.3 Saffran (1985) proposed a similar hypothesis in order to account for the fact that a patient, LL, was more likely to pronounce a vowel digraph correctly if the correct pronunciation yielded a word as opposed to a nonword and was more likely to pronounce it incorrectly if the incorrect pronunciation yielded a word as opposed to a nonword. She argued that this lexicalization effect can be best explained by assuming that OPC procedures generate alter-

3 Here we do not wish to argue that the phoneme string generated by OPC mechanisms can only be pronounced via reference to the Phonological Output Lexicon. We are merely proposing that the OPC mechanisms can be used to activate phonological representations for output.


native mappings that are referred to the Phonological (Output) Lexicon; then, if a lexical match is obtained, the word is pronounced, and if not, the pronunciation is generated from the output of the OPC mechanism.4 This proposal can also account for LL’s phonologically related word errors in reading; for example, she read lose as “loss” and sew as “sue”. This type of reading error, particularly in response to low frequency words, is expected because all entries in the Phonological Output Lexicon that correspond to the phoneme strings assembled by the OPC mechanisms would be activated, and the entry with the activation level closest to threshold could be made available for further processing.

On the basis of the proposal outlined thus far, phonologically plausible errors+ither words (when input from OPC mechanisms results in threshold-level activation for an entry in the Phonological Output Lexicon) or nonwords-should result whenever semantic information is insufficient to activate the target entry. Hence, the proposal alone cannot account for fluent and accurate reading without comprehension, as reported for patients such as WLP (Schwartz et al., 1980). To account for the (virtual) absence of reading errors despite very impaired comprehension in these cases, we propose that input from the OPC mechanism summates with partial information from the semantic system to select correct entries in the Phonological Output Lexicon.’

In summary, the alternative account-the “summation hypothesis”- of accurate reading with impaired semantics that is considered in this paper assumes that: (1) lexical-phonological representations in the output lexicon are activated in parallel; (2) activation comes from two sources, the semantic system and the OPC mechanism; (3) the level of activation of each entry depends on both the degree of similarity to the target semantic representation (individual semantic features activate lexical- phonological representations of all items that have that feature) and the degree of similarity to the phonological strings(s) assembled by OPC procedures; and (4) selection of a particular lexical representation for production depends on the total activation from the two sources of input and on the threshold of activation of the entry. These assumptions underlie the proposal that accurate oral reading could result from the summation of (even partial) information from OPC mechanisms and (even partial) semantic information, which together activate corresponding entries in the Phonological Output Lexicon to threshold levels. So, for example,

4 It could be argued that the input from the OPC mechanisms to the Phonological Output Lexicon is mediated by the phonological output buffer. However, this proposal would require that we assume “feedback” from a response buffer to the Phonological Output Lexicon- an otherwise unmotivated assumption.

’ The degree of impairment to the semantic system and to the OPC mechanisms will, of course, vary from patient to patient and will influence the pattern of performance, as discussed in further detail under General Discussion.


the word girl might activate an impaired semantic representation that specified only, say, (HUMAN, YOUNG), which in turn activates lexical- phonological representations for “girl,” “boy,” “child,” etc., and simul- taneous output from the OPC mechanisms would activate lexical-phonological representations for “girl,” and perhaps “gull,” “gill,” “Jill,” and “curl” (to a lesser extent). Since the summated activations from the semantic and sublexical OPC processes favor the lexical entry “girl,” it would be the most likely entry to be selected for production.

Because the summation hypothesis and the hypothesis of direct lexical connections lead to many (although not all) of the same predictions in reading, spelling, and comprehension, it is not clear that they could be easily distinguished on empirical grounds alone. Furthermore, they might not be truly alternative explanations, since both types of mechanisms could contribute to oral reading. Despite these difficulties, we explore in this paper the extent to which the pattern of performance at issue-correct reading of irregular words that are not understood perfectly+an be adequately explained by assuming an interaction between sublexical and semantic mechanisms without assuming the existence of direct connections between input and output lexical representations. We report detailed analyses of reading and comprehension performance by JJ, who showed a striking discrepancy between categories in the production of semantic errors in all naming and comprehension tasks, but who nonetheless read (and to a lesser extent, spelled to dictation) all categories of words tested. We show that JJ’s pattern of performance on various lexical tasks is consistent with predictions of the summation hypothesis. We conclude by arguing that the earlier cases in the literature, of brain-damaged subjects who read or spelled words that they failed to understand, can also be explained by the summation hypothesis. Finally, we provide evidence for the hypothesis that there is an interaction of different types of information in activating lexical representations, whether or not direct connections between input and output lexical representations also exist.

CASE REPORT

Social and Medical History

JJ is a 67-year-old, right-handed male. He is a retired corporate ex- ecutive whose formal education included high school and 2 years of college. JJ sustained a thromboembolic stroke 7 months before the present study began. A CT scan 2 days after his stroke revealed a large infarct involving nearly the entire left temporal lobe, as well as two left basal ganglia region infarcts, one involving the head of the caudate and another extending from the anterior limb of the internal capsule laterally into the putamen. Neurological symptoms were primarily in the area of language; examination was negative for dysarthria, ataxia, and limb weakness.


Ophthalmological evaluation 11 months post onset revealed a very slight reduction of the right visual field.

The patient’s significant medical history includes insulin-dependent di- abetes, hypertension, and atria1 fibrillation. JJ lives with his wife in their own home and is independent in daily activities in the community, such as driving and shopping.

Clinical Speech and Language Evaluation

JJ was initially seen at the Medical Rehabilitation Center of Maryland 1 month after his stroke. At that time, his spontaneous speech was char- acterized by fluent English jargon, intermingled with occasional phonemic paraphasias or neologisms. Only commonly used social expressions were accurate. He showed profoundly impaired naming and comprehension of printed and auditory stimuli on the Boston Diagnostic Aphasia Exami- nation (BDAE; Goodglass & Kaplan (1972)). Articulation, phonation, and prosody were normal. Performance on the Peabody Picture Vocab- ulary Test (Dunn & Dunn, 1981) could not be scored, because JJ did not reach basal level.

By the time the present investigation was initiated at 7 months poststroke, JJ had improved in all areas of language, but still had substantial, persisting impairments. Spontaneous speech consisted of fluent, grammatical sentences with frequent circumlocutions and semantic paraphasias. Performance on the BDAE revealed deficits in tasks of auditory word/picture matching (59/72 correct), following commands (7/15 points); understanding spoken stories and acontextual questions (7/12 points), repeating phrases (l/16 correct), picture naming (93/114), understanding printed sentences (6/10), and spelling to dictation (7/10). He received a score of 37/60 on the Revised Boston Naming Test (Goodglass, Kaplan, & Weintraub, 1983), which corresponds to the moderate range of severity of impairment. His score of 11/36 on the Modified Token Test (DeRenzi & Falgioni, 1978) was in the “severe” range of impairment. His score on the latter test administered with printed stimuli was 17/36. In contrast, his oral reading of text was essentially normal: He made only occasional morphological errors in oral reading of sentences and para- graphs, which he consistently self-corrected. His reading rate was also essentially normal; he read an unfamiliar 133 word passage at a rate of 140 words/min (normal for non-brain-damaged adults is 160-170 words/min (Yorkston, Beukelman, & Bell, 1988); normal for geriatric adults is generally considered to be somewhat lower). He also performed normally (262/270; 97% correct) on a printed word/pseudoword word lexical decision task in which each pseudoword (pronounceable nonword) was created by changing a single letter of a word matched in frequency, word class, and length to a word on the same list. On this list, he accepted six pseudowords (e.g., anound) and rejected only two words: perhaps


and amidst. His age-corrected score of 33/36 on Raven’s Coloured Pro- gressive Matrices (Raven, 1962) was well above the normal mean of 29, consistent with intact visual perception and nonverbal reasoning.

The current investigation took place between 7 and 13 months after his stroke. Throughout that period (as reported in detail in Hillis & Caramazza (in press, a), JJ showed severe difficulty naming pictures of objects and understanding their names, except for in the category of animals. (The spared category specifically concerned animals and not living things more generally.) By 13 months poststroke, he made no errors in oral naming of animals (land animals, water animals, or birds), but made about 30-40% errors in oral naming of pictures in other categories (fruits, vegetables, prepared foods, transportation, clothing, body parts, and fur- niture). Similarly, written naming was also 100% correct for animals and 60-95% correct for other categories, when misspellings were not penalized if they did not interfere with a naive judge’s recognition of the word (of those scored as correct, 83% were correctly spelled and the remainder were phonologically plausible; e.g., whale + whayle). All of his oral and written naming responses that were not recognized as the correct word were semantically related words, such as “banana” given in response to a picture of grapes. Furthermore, JJ made no errors in response to animals in word/picture verification tasks, but made 19% errors in response to semantically related pictures presented with words in other categories. In contrast, his oral reading of words in all categories (of the same concrete nouns tested in naming) was flawless. These stimuli included some words that were orthophonologically irregular in the sense that they could not be pronounced by applying the most frequent grapheme-to-phoneme correspondences for individual letters or letter sequences (norms from Berndt, Reggia, & Mitchum (1987)). Examples of irregular names include leopard, giraffe, bear, swan, sweater, glove, suit, stomach, mustache, shoul- der, bread, cookie, soup, pear, and drawer. With these stimuli JJ also showed no difference between categories in spelling to dictation; all but one of his responses were either correct (109/144; 76%) or phonologically plausible (e.g., sofa * soafu; 34/144; 24%).

EXPERIMENTAL INVESTIGATION

READING

Studies were designed to test the hypothesis that JJ’s correct oral reading of irregular words that he did not completely understand could be accounted for by the summation hypothesis, that is, by assuming that activation of phonological representations can be supported by summation of incomplete semantic information and inexact or incomplete phonological information assembled from OPC procedures. Several expectations follow from this proposal. First, he should correctly read all words that


he understands (even if not perfectly), because the lexical-phonological representations for these stimuli should receive activation from both the semantic system and the OPC procedures. By this reasoning, he should also occasionally produce words that are both semantically and phonologically similar to the stimulus, particularly in those cases where there exists a semantically and phonologically similar word that is higher in frequency (or otherwise more available) than the target response. Second, when JJ fails to understand a word at all, his reading response should reflect application of OPC procedures. Thus, words that correspond ex- actly to a phonological string assembled by OPC procedures should be correctly read, whereas very irregular words should elicit phonologically plausible responses (e.g., one * “own”).

Method Testing involved two primary tasks: (1) oral reading of lists of words, compiled to measure

the effects of various orthographic and lexical parameters; this task was completed 7 to 10 months after his stroke; and (2) oral reading and comprehension of lists of words, chosen to evaluate the relationship between comprehension and reading performance; this task was completed between 7 and 13 months after his stroke. For oral reading, he was presented with individual printed words with no time constraints. Most of the word lists were from the Johns Hopkins Dyslexia Battery (Goodman & Caramazza, 1986b). For comparison of oral reading and comprehension, JJ was asked to read aloud stimuli from standardized tests of reading comprehension (which were administered to assess his understanding on a sub- sequent occasion), or to define words on lists which he had previously read. For each comparison, comprehension and oral reading were assessed within the same week. Analysis of the results focused on the relationship between accurate oral reading and two independent variables: comprehension (intact, partially impaired, or completely nonfunctional) and orthophonological regularity.

Results

Errors in Oral Reading

The summation hypothesis predicts that two types of errors might occur when semantic information is insufficient to (alone) select the correct lexical-phonological representation on a consistent basis: (1) phonologically plausible errors when the word is irregular and poorly understood and (2) phonologically and semantically related words when the stimulus word is partly understood. To test for the predicted pattern, a large corpus of errors was recorded, by administering the Dyslexia Battery. This as- sessment also allowed us to identify other lexical and orthographic parameters that affected his reading. The only expectation regarding lexical factors that followed from the summation hypothesis is that regular words should be read more accurately than highly irregular words (assuming that he would fail to access semantic information for at least a portion of both sets). Word class or concreteness might also affect reading performance if his comprehension was influenced by these variables. Below


TABLE 1 DISTRIBUTION OF JJ’s READING ERRORS BY TYPE OF ERRORS

Visually dissimilar words Visually similar word responses

Phonologically similar Semantically related

Morphological errors Other

Semantically unrelated Phonologically dissimilar

Errors on words 0 (0)

18 (62)

14 11 3 4 0

Nonword (phonemic) errors 11 Phonologically implausible 0 Phonologically plausible 11

Omissions (“don’t know”) 0

Total 29

Errors on nonwords Visually dissimilar word responses Visually and phonologically similar words Phonologically implausible nonword responses

Single phoneme error Multiple phonemes

Omissions (“don’t know”)

Total

N

(37.9)

(0) (100)

(0) (57.1) (42.9)

(0) (100)

Note. Percentage of errors given in parentheses.

we show that expectations regarding both error types and the influence of orthophonological regularity were borne out.

Error types. The distributions of JJ’s error types on the Dyslexia Battery are reported in Table 1. His responses included many plausible, but inaccurate, pronunciations, attributable to application of valid OPC procedures (e.g., drama + [draema]). Several of these errors were correct pronunciations except for incorrect syllable stress (e.g., he stressed the second syllable of both instinct and absence). All of his remaining errors on the battery were phonologically/visually similar words, many of which were also semantically related to the stimulus. For instance, he read jury as “judge” and epistle as “episcopal”. His morphological errors (e.g., offense + “offending”; nature + natural; seven + “seventh”) could also fall into this class of errors. The few errors in response to nonwords were visually and phonologically similar words (e.g., chench elicited “clinch”) or single phoneme errors (ghurb + [grb]). Notably, all of his errors shared at least the initial phoneme with the target.


TABLE 2 JJ’s READING PERFORMANCE AT I MONTHS POSTSTROKE

% Correct

Part-of-speech list Open class words (84)

Nouns (28) Verbs (28) Adjectives (28)

Functors (20) Nonwords (68)

Nonhomophones (34) Pseudohomophones (34)

Visually Similar (17) Visually Nonsimilar (17)

92.9 96.4 92.8 89.3

90.0 89.7

85.3 94.1

94.1 94.1

Concreteness list Concrete words (21) 100.0 Abstract words (21) 95.2

Word length list Four-letter words (14) 92.9 Five-letter words (14) 92.9 Six-letter words (14) 92.9 Seven-letter words (14) 78.6 Eight-letter words (14) 78.6

Word frequency list High frequency (91) 97.8 Low frequency (91) 91.1

Note. Number of stimuli given in parentheses.

Lexical and orthographic effects. There were no significant effects of word class, word length in letters, concreteness, or word frequency, although there were tendencies to favor nouns, concrete words over abstract words, four- to six-letter words over seven- to eight-letter words, and high frequency over low frequency words (Table 2). His overall accuracy of 92.3% suggests that effects of at least some of these parameters might have been masked by ceiling effects.” Similarly, there was a trend for

’ On an earlier test of the Dyslexia Battery at 4 months post onset, JJ’s reading accuracy was significantly influenced by concreteness and word length in letters, but was not influenced by grammatical word class or frequency. On a list of two-syllable nouns counterbalanced for concreteness, frequency, and letter length, he read concrete words more accurately than abstract words (76% vs. 57% correct). On a list of 14 words, each of length from four to eight letters, matched for frequency and word class, his accuracy deteriorated as a function of letter length (Xt = 8.25; p < .005; Mantel-Haenszel test; Mantel & Haenszel (1959)).


TABLE 3 JJ’s READING PERFORMANCE AS A FUNCTION OF ORTHOPHONOLOGICAL REGULARITY“

Regular, consistent Low frequency High frequency

Regular, inconsistent Low frequency with higher frequency exception High frequency with lower frequency exception

Exception words Low frequency High frequency

Orthographically strange Low frequency High frequency

Oral reading Comprehension

Number Number correct (%I correct (%)

359/360 (99.7) 102/120 (89.2) 179/180 (99.4) 180/180 (100)

175/180 (97.2) 55/60 (91.7) 87190 (96.7) 88/90 (97.8)

X4/180 (91.1) 54/60 (90.0) 79190 (87.8) 85/90 (94.4)

128/150 (85.3) 43/50 (86.0) 72190 (80.0) 56160 (93.3)

a Each list was presented three times for oral reading and once for comprehension; there were 120 different regular words; 60 different regular, inconsistent words; 60 exception words; and 50 orthographically strange words, as defined by Seidenberg, Waters, Barnes, & Tanenhaus (1984).

pseudohomophones (e.g., hunnee) to be read more accurately than nonhomophonic nonwords (e.g., hannee) (94% vs. 85%; Xf = 1.4; NS), but both types of nonwords were read fairly well.

On lists compiled to measure orthophonological regularity in terms of the consistency with which the rhyme (vowel plus final consonant cluster) is given the target pronunciation, JJ showed a small, but reliable, sen- sitivity to this dimension at 11 months poststroke. These results are summarized in Table 3. He misread only 1 of 240 words that are both regular (in the sense that they follow the most frequent grapheme-to-phoneme correspondences) and contain a rhyme that is consistently given the same pronunciation (e.g., lake). He read these words slightly more accurately than regular words with rhymes that are inconsistently given the target pronunciation (e.g., cook, because -ook can be pronounced as in “spook”). Reading of regular, consistent words was significantly more accurate than reading of words that have irregular pronunciations (e.g., have) (X: = 16.89; p < .OOOl) and significantly more accurate than reading of “orthographically strange” words, which have spellings of the rhyme that are unique to that word (e.g., style) (XT = 31.26; p << .OOOl). There was also a significant difference between “regular, inconsistent” words and “exception” words (XT = 5.06; p < .03). All of these


lists were matched for frequency and length; all words had three to five letters. These lists were presented at 10 months postonset. At that time, his errors on such short words were limited to phonologically plausible errors (e.g., Were + “we’re”; says -+ [serz], rhyming with pays). It is also worth noting that the higher level of performance in oral reading than in comprehension accuracy was highly significant for regular, consistent words (X: = 51; p << .OOOl) and was of borderline significance for regular, inconsistent words (Fisher’s exact test: p = .07; odds ratio = 3; confidence interval = 0.76-13.3), but did not approach significance for exception words or “orthographically strange” words.

Oral Reading as a Function of Comprehension

The clearest and strongest prediction that follows from the summation hypothesis is that JJ should misread only those words for which he cannot access any semantic information. Note that it does not follow that he would misread all words to which he made comprehension errors (especially errors that indicated some comprehension of the word, as was true for his frequent semantic errors in word/picture verification), since even partial semantic information might be sufficient, along with the available sublexical information, to select the correct entry in the output lexicon. Hence, we first looked at words that JJ misread and tested the prediction that he would also misunderstand these words.

JJ was asked to read orally all the words from the Peabody Picture Vocabulary Test, just prior to standard administration with printed words. He misread only 7/175 words, all of which he read as phonologically plausible nonwords. Consistent with predictions from the summation hypothesis, his comprehension performance on these words was very poor (no better than the chance level of 25%); he matched 6/7 words that he mispronounced to an incorrect picture. For example, he read hovering with a long/o/ (i.e., [houvarn]) and matched it to a picture of a bird feeding worms to her offspring (as opposed to a correct picture of a bird hovering in the air). The 168/175 correctly pronounced words also included 18 words that he matched incorrectly to a picture.’ Some of these words were orthophonologically irregular. On the summation hypothesis, JJ’s accurate oral reading of (irregular) words that elicited errors in word/picture matching can be explained by assuming that he had some understanding of these words which, together with information from the OPC procedures, resulted in the activation of the correct lexical-phonological representation. That JJ might have had partial semantic information about the words in question is not unlikely: all the incorrect picture

’ As we would expect, JJ was much more likely to select an incorrect picture to a word that he mispronounced than to a word he correctly pronounced (6/7 vs. M/168; X,” = 15; p < .OOOl; Fisher’s exact test: p < ,002; odds ratio = 8; confidence interval = 2.1-30.6).


foils he selected were semantically related to the word. For example, in response to competition he chose a picture of discussion/debate, and in response to attire he chose a picture of a handbag. Unfortunately, the latter result cannot be used to argue that JJ did in fact have some semantic information for the items for which he chose a semantically related response, because nearly all of the available choices on this test are semantically related items. Therefore, in order to test the prediction that he partially understood irregular words that he correctly read, we used another task.

JJ was asked to read each stimulus and then choose the correct response in a synonym matching test (the Vocabulary subtest of the Gates- MacGinitie Reading Test, Survey E; Gates & MacGinitie (1965))) in which the foils include a visually similar word, a semantically related word, and a completely unrelated word. On this test, JJ always selected either a correct word or a semantically related foil for words that he read correctly. Specifically, he correctly pronounced all but 2 of the 50 stimulus words, but he failed to select the correct synonym for 17 (34%) of the items. Again, all of his errors in response to words he had read correctly sug- gested partial understanding of the word; for example, he selected blossom for nectar and nap for lullaby.

JJ did not, however, make a sufficient number of reading errors on these tests to reliably test the related prediction that he would consistently mispronounce (at least irregular) words that he misunderstood entirely and corrctly read all words that elicited some semantic information. To address this question, JJ was asked to define the 290 different words from lists constructed to measure the effects of orthophonological regularity. He then read each word after defining it. Definitions were recorded and independently scored by two examiners, one of whom was naive to the purpose of the study and to the hypotheses that had been formulated. Interjudge reliability between scorers was 93.8%, so only the scores of the naive judge are reported.

Although JJ’s oral reading performance was influenced by the regularity and the consistency of pronunciation of the stimuli, there was no hint of an effect of these dimensions on his comprehension (Table 3). Instead, as predicted, JJ correctly pronounced all of the 260 words for which his definitions revealed some comprehension. He correctly pronounced even “exceptional” and “orthographically unique” words that invoked impre- cise definitions which were judged to be “in the ballpark” or incomplete. For instance, he defined have as “to take something” and sword as “a weapon. , . I can’t recall any more,” and pronounced both of the stimulus words correctly, even though he was unable to formulate more precise definitions.

On the other hand, JJ did not mispronounce ail of the words for which his definitions indicated a total lack of comprehension; rather, he correctly


TABLE 4 JJ’s ORAL READING AS A FUNCTION OF COMPREHENSION

Comprehension

Accurate

Partially correct

or ambiguous Wrong

(no response or unrelated)

Read correctly 78 Read incorrectly 0

Total 78

Read correctly Read incorrectly

Total

43 0

43

Read correctly 28 Read incorrectly 0

Total 28

Read correctly Read incorrectly

Total

31 0

31

Regular, consistent 29

0

29

Regular, inconsistent 12 0

12

Exception words 26

0

26

Orthographically strange 12 0

12

12 1

I3

Total

58 2

60

54 6

60

43 7

50

pronounced 50% (15/30) of the words for which he could not formulate any sort of definition. Examination of these 15 words that were correctly pronounced despite lack of understanding indicates that correct reading in these cases could well have been supported by application of OPC procedures: 12 of these words were regular with consistently pronounced rhymes and 3 were regular with inconsistently pronounced rhymes. For example, in response to loom he said, “It’s very, very vague; I can’t remember it at all . . . loom?” In contrast, he never correctly pronounced exceptional words that he could not define at all. Table 4 illustrates this relationship between orthophonological regularity, accuracy of oral reading, and comprehension.8

The results of the latter task also allow a test of the summation hypothesis’ prediction that in the absence of semantic information, pronun-

’ The same 290 words were presented auditorially for definitions the following week. JJ’s comprehension of spoken words was essentially identical (90% correct) to his comprehension of printed words.


ciation should rely on OPC procedures alone. JJ showed precisely this pattern. His reading of regular words that he failed to understand was very good, whereas his reading of exceptional and orthographically unique words that he misunderstood reflected application of OPC procedures. Thus, for example, in attempting to define pint JJ said, “Doesn’t speak anything to me,” and then read it as [pmt] (rhyming with “mint”). Sim- ilarly, for the stimulus plaid, his response was: “I’m not sure,” and then he pronounced it “played.” This last type of error, substitution of a high frequency word that is also phonologically plausible, is to be expected on the assumption that output from the OPC mechanism can activate entries in the Phonological Output Lexicon. In the “absence” of semantic information, the only input to lexical-phonological representations would be from OPC procedures, which in some cases would be sufficient to activate to threshold high frequency words that match one of the possible pronunciations assembled by the OPC mechanism. Thus, we would expect some irregularization of words that are not understood, such as JJ’s reading of seize as “size” (thus pronouncing ei as in “stein”), when he failed to show any understanding of the word. This incorrect reading of low frequency words when an alternative pronunciation is a higher frequency word is also revealed in the errors of other patients who have been reported to have relatively accurate oral reading in the face of poor comprehension. MP (Bub et al, 1985), for example, misread bead as “bed”. These types of errors are consistent with the possibility that OPC procedures assemble alternative pronunciations for the output lexicon.

Also consistent with the summation hypothesis, these data (combining various levels of orthographic regularity) show that JJ was much more likely to read a word correctly if his definition demonstrated either accurate or partial comprehension than if his definition lacked any evidence of comprehension (XT = 135; p << .OOOl; Fisher’s exact test: p << .OOOl).

Conclusions from Reading Studies

JJ’s correct reading of most of the nonwords presented indicates that he was able to assemble a correct or plausible pronunciation by sublexical OPC procedures. This result suggests that he may have relied on OPC procedures to read many real words when he was unable to access correct lexical and/or semantic representations. Indeed, his phonologically plausible errors in reading are consistent with this conclusion.

Although application of OPC procedures alone would support oral reading of certain words, the application of such procedures cannot account for JJ’s accurate reading of words with exceptional pronunciations. Accurate pronunciation of exception words and correct syllable stress on polysyllabic words would seem to require access to the phonological representation of the word in the output lexicon. Yet, JJ’s mistakes in comprehension of exceptional words and the polysyllabic words (from the


PPVT) that he read correctly indicate that information from the semantic system would not have been sufficient in itself to activate the target entry in the Phonological Output Lexicon. That is, his semantic errors in word/picture matching and synonym matching and his partially correct definitions indicate impoverished semantic information for these items. However, a crucial expectation derived from the proposed model of lexical processing is that partial semantic information should result in the activation of a number of semantically related lexical-phonological representations, as well as the correct entry itself (see Caramazza & Hillis (1990) and Hillis et al. (1990) for discussion). In such cases, the selection of the target lexical-phonological representation must depend on additional information from some other source. This conclusion is further strengthened by the fact that normal readers do not substitute exact syn- onyms in oral reading. These considerations invite the conclusion that the selection of a lexical-phonological representation depends on the summated activation from (partial) semantic and phonological information, the latter produced by the application of OPC procedures. For JJ, the hypothesized interaction between semantic and phonological information would account for his correct pronunciation of irregular words that are only partially understood. For example, incomplete understanding of the word competition (which JJ matched to a picture of a discussion on the PPVT) might activate equally a number of related entries in the Phono- logical Output Lexicon, such as representations for “game,” “discussion,” “debate,” “argument,” “competition,” etc., so that even imperfect phonological information assembled by OPC procedures, contributing additional activation to the correct representation among these alternatives, might well be sufficient for that representation to reach threshold for production. This hypothesis also predicts that there should be incorrect selections of words that are both semantically and phonologically related to the target response. And, in fact, such errors are well represented in the corpus of errors produced by JJ (e.g., epistle + “episcopal”).

In summary, JJ’s performance closely conformed to predictions derived from the summation hypothesis. Specifically, he correctly read regular, consistent words (irrespective of how well he understood them), as well as inconsistent and irregular words for which he demonstrated at least partial understanding. His few errors on the latter type of words were both semantically and phonologically related to the target. Finally, in the absence of semantic information, inconsistent and irregular words elicited phonologically plausible errors-i.e., they were seemingly read by the application of OPC procedures.

SPELLING

The results of reading tasks are consistent with the hypothesis that JJ’s relatively intact oral reading is based on (sometimes impaired) information from the semantic system, along with information from OPC procedures


which serves to ‘triangulate’ the correct response from the set of candidates activated by the semantic representation. A similar hypothesis may be offered for JJ’s relatively accurate spelling to dictation, in comparison to his written naming and comprehension performance. On this hypothesis, he should correctly spell words that he understands (because both the semantic system and sublexical procedures would contribute activation) and should produce phonologically plausible responses (i.e., correct responses to regular words and errors of the type “laugh” + luff in response to irregular words) when there is no significant contribution from the semantic system. This hypothesis was evaluated through the analysis of JJ’s spelling and comprehension performance.

Method JJ spelled to dictation essentially the same lists of words that were administered for

reading, in order to determine the influence of various lexical and orthographic factors on spelling accuracy. These tasks were administered at 11 months poststroke. In place of lists compiled to determine the effects of orthophonological regularity, spelling stimuli included a list from the Johns Hopkins Dysgraphia Battery (Goodman & Caramazza, 1986b), which consists of 30 words with a high probability of correct spelling by applying the most frequent phoneme-to-grapheme mappings (hereafter, regular words), balanced in length and frequency with 80 words with a low probability of correct spelling (hereafter, irregular words).

Results

Lexical Effects and Error Types

Following the rationale presented for reading, we predicted that JJ would spell nonwords and orthographically regular words more accurately than irregular words and make phonologically plausible errors in response to irregular words that he did not understand.

These expectations were borne out: JJ accurately spelled 79.4% (27/34) of nonwords (i.e., in a phonologically plausible fashion), but he correctly spelled only 34.5% (29/84) of the words matched for length. Further, on 5/7 of his misspellings of nonwords, he erred by only one phoneme (e.g. ,/bsk/ (“berk”) -+ berge). Another significant determinant of spelling accuracy was the probability of spelling the word correctly by applying the most frequent POC mapping: He spelled regular words more accurately than irregular words (83% vs. 64% correct, respectively; Table 5). Also as predicted, the most prominent feature of his spelling was that nearly all (more than 90%) of his errors were phonologically plausible renditions of the auditory stimulus (e.g., “grew” + grue, “loaf” + lough, “riot + wriett, phase + fais), and 88% of his implausible errors were off by only one feature of one phoneme. Most often, an implausible error in conversion involved the voicing feature (e.g., “cheer” + jeer, “cloud” + clout, “debt” + ded). Taken together, these data are consistent with the hypothesis that JJ’s dictation performance surpassed his written nam-


TABLE 5 JJ’s SPELLING PERFORMANCE AT 11 MONTHS POSTSTROKE

% Correct

Part-of-speech list Open class words (84) 34.5

Nouns (28) 53.6 Verbs (28) 28.6 Adjectives (28) 21.4

Functors (20) 65.0 Nonwords (34) 19.4

Concreteness list Concrete words (21) 33.3 Abstract words (21) 33.3

Word length list Four-letter words (14) 57.1 Five-letter words (14) 64.3 Six-letter words (14) 42.9 Seven-letter words (14) 42.9 Eight-letter words (14) 28.6

Word frequency list High frequency (91) 60.3 Low frequency (91) 39.0

Probability List High probability words (30) 83.3

High frequency (15) 80.0 Low frequency (15) 86.7

Low probability words (80) 63.8 High frequency (40) 77.5 Low frequency (40) 50.0

Note. Number of stimuli given in parentheses.

ing and comprehension performance, because his spelling performance was aided by relatively intact POC procedures.

Spelling as a Function of Comprehension

As would follow on the basis of the summation hypothesis, JJ was unable to spell low probability words that he was unable to define at all, and he spelled correctly a few irregular words that he had defined in- adequately (e.g., book, defined as “a source of information”-a definition that is equally compatible with semantic coordinates of “television,” “ra- dio,” “ newspaper, ” “magazine,” etc.). The latter, but not the former, result would also be predicted by the direct route hypothesis. Another result that was expected from the hypothesis that semantic information


TABLE 6 JJ’s SPELLING ACCURACY AS A FUNCTION OF COMPREHENSION AND

PHONO-ORTHOGRAPHIC REGULARITY

Comprehension

Partially correct Wrong Accurate or ambiguous (no response or unrelated) Total

Regular” Spelled correctly 17 5 3 25 Spelled incorrectly 1 1 3 5

Total 18 6 6 30

Irregula? Spelled correctly 38 13 0 51 Spelled incorrectly 2 5 22 29

Total 40 18 22 80

a High probability of correct spelling by applying the most common phoneme-to-grapheme mappings.

b Low probability of correct spelling by applying the most common phoneme-to-grapheme mappings.

and orthographic information from sublexical POC procedures converge to address the output lexicon was that JJ’s spelling accuracy was clearly influenced by the degree of his understanding, and this effect was stronger for irregular than for regular words (Table 6).

There was, however, one feature of JJ’s spelling performance that was not predicted by the summation hypothesis: He misspelled some words for which he demonstrated good comprehension. Specifically, he misspelled 3 of the 58 words that he defined accurately and 6 of the 25 words that elicited partly correct or ambiguous definitions. For example, he defined “trade” as “to exchange” but spelled it as tread (with ea as in break), he defined “thief’ as “one who steals” but spelled it as thiefe, and he defined “type” as “tapping a device for numbers and letters” but spelled it as tipe. Here, he seemed to have accessed relatively intact semantic information, but nonetheless relied on POC procedures to spell the word.’ To explain these errors, it is necessary to postulate that JJ had a deficit at the level of the Orthographic Output Lexicon, as well as

9 It should be noted that this sort of definition does not provide convincing evidence that JJ’s understanding of the word was unscathed, i.e., equivalent to his premorbid understanding. However, it demonstrates that he had some comprehension of the word that should activate a lexical representation for output. In fact, all of our arguments concerning the definitions hinge only on demonstrating specific patterns of performance associated with instances in which he had some understanding versus instances in which he had virtually no understanding of the word.


to the semantic system.‘” This additional locus of impairment is also indicated by the significant effect of word frequency on spelling accuracy (as reported in Table 5). Note that the frequency effect did not appear in response to regular (high probability) words.

Conclusions from Spelling

The influence of regularity on spelling accuracy, together with JJ’s frequent phonologically plausible errors, provide evidence that JJ often relied on sublexical POC procedures for spelling. A reliance on POC procedures in spelling might result from damage to any one of several components of the spelling process, from accessing the appropriate entry in the Phonological Input Lexicon (in spelling to dictation) to accessing semantic representations, to accessing entries in the Orthographic Output Lexicon. The relationship between spelling accuracy and comprehension indicates that JJ used POC procedures more often to spell words that he failed to understand than to spell words that he understood. However, he correctly spelled some low probability words that he only partly understood, as indicated by his definitions and also by semantic errors in word/picture verification tasks in earlier testing. Thus, for example, he correctly spelled “wrist,” but he accepted a picture of an elbow as the referent of “wrist.” These errors could be explained by assuming a direct route between input and output lexicons in spelling. But the fact that correct spelling of irregular words was limited to words that were at least partially understood follows more directly from the hypothesis that (partial) semantic information, together with relatively intact POC procedures, might allow selection of correct entries in the Orthographic Output Lex- icon. However, to explain JJ’s occasional misspellings of words that he seemed to understand, we must also assume that this combined input was not always sufficient to activate. the appropriate lexical-orthographic representation, perhaps due to an additional deficit at this latter level of processing.

JJ’s performance in spelling high frequency words can be explained by assuming that semantic information and sublexical POC information sum- mate in the process of activating (more available) entries in the Ortho- graphic Output Lexicon, so that the correct entry is selected for production if (1) semantic information is intact; (2) the spelling matches the output

I” Alternatively, as pointed out to us by Chris Barry, these errors might occur as a result of partial matching in the interaction between the activated lexical information and the activated POC information, since all of these errors share some letters of the target word. Afthough ea (in k-ad) is hardly the most common spelling of /el/ (in the stimulus “trade” or /treld/), it is one possible mapping; since it rarely occurred in JJ’s spelling of words containing /eI/, this single example may reflect the normal probability of selecting various orthographic renditions of /eI/. It may also be worth noting that “tread” was not understood at all by JJ, and was misspelled wed.


from POC procedures, more frequently the case if the word if regular, or (3) partial semantic information and partial POC information together provide sufficient constraints to select the target response.

GENERAL DISCUSSION

We have presented analyses of the performance of a neurologically impaired patient who exhibits a dissociation between impaired naming and comprehension and relatively spared oral reading and spelling to dictation. Previously reported similar patterns of performance have been interpreted as evidence for proposing nonsemantic, “direct” connections between input and output representations for reading and spelling of irregular words. JJ’s performance does not rule out this direct route proposal. However, we have shown that JJ’s ability to read (and spell) irregular words for which he fails to access intact semantic information can also be accounted for by proposing that partial semantic information summates with information concerning valid correspondences between orthography and phonology to result in correct selection of lexical-phonological representations for production.

In fact, the summation hypothesis proposed here not only made it possible to account for those features of JJ’s performance that have previously been interpreted as support for the hypothesis of direct, nonsemantic connections between input and output lexicons, but could also account for specific aspects of his reading and spelling performance that do not follow in obvious (non ad hoc) ways from the direct connections hypothesis. To review, the proposal that information from sublexical conversion mechanisms combines with information from the semantic system to access lexical-phonological representations allowed two specific predictions about reading performance in the case of a deficit to semantics with intact OPC mechanisms: The patient should correctly read all words that activate at least partial semantic information and should assign regular, or valid, pronunciations to words for which IZU semantic information is available. The latter expectation would be supported if the patient were to produce correct responses to “regular, consistent” words and to many regular, inconsistent words, and to produce phonologically plausible errors in response to irregular words, that are not understood. JJ demonstrated just this pattern of performance. He misread only those words for which he apparently obtained IZO semantic information and correctly read only regular words and those irregular words that elicited some, if incomplete, semantic information. A comparable case was made for postulating that JJ’s spelling performance reflected the activation of lexical-orthographic representations through the summation of inputs from the semantic component and sublexical POC procedures. Thus, the proposal that lexical- semantic and sublexical conversion procedures interact in the process of accessing lexical representations for output can account for JJ’s reading


and spelling performance. Can this proposal also account for the data that have been previously reported as evidence for the nonsemantic, lexical route in reading?

Perhaps the first case of preserved oral reading in the face of severe semantic processing impairment was reported by Schwartz et al. in 1980. They described a patient, WLP, with a progressive dementia, who, like JJ, read fluently and quite adequately despite very limited comprehension of the material. Warrington and McCarthy (1983), Bub et al. (1985), Funnel1 (1983), and McCarthy and Warrington (1986) have described similar, if less severe, cases. The performance by each of these patients was interpreted as evidence of direct correspondences between orthographic and phonological lexical representations (see Shallice (1988) for a summary of the cases). In each case, the interpretation is based on the premise that the patient’s comprehension was so poor that it did not permit adequate access to lexical-phonological representations for output. However, this premise is not beyond challenge. There are indications, from samples of spontaneous speech and/or performance on various lexical tasks, that each of the patients understood something about many, if not all, words. For example, errors by WLP (Schwartz et al., 1980) in word/picture matching tasks were predominantly within-category semantic errors, such as consistent selection of a picture of a small pet in response to the name of a different small pet, indicating that she did obtain some semantic information about the words she failed to understand normally. Similarly, Funnell’s (1983) patient, WB, was unimpaired in word/picture matching with unrelated foils and much better at matching a word to the most closely associated word when the foil was unrelated than when the foil was related to both words (e.g., orange/lemon-tangerine). KT (McCarthy & Warrington, 1986) and MP (Bub et al., 1985), along with WLP were able to sort printed words into categories with better than chance accuracy, and KT pointed to named pictures with greater than chance accuracy. MP’s categorization performance was only about 50% (with chance level of 33%), but then her oral reading of irregular words was only 41% correct. Therefore, to account for her reading performance on irregular words on the basis of partial semantic and partial phonological information, we need only postulate that MP was able to access some semantic information for about 40% of words that she could read. Other aspects of MP’s performance that lend further credence to the assumption that partial semantic information facilitates her reading include her accurate and fluent sentence reading, compared to her often inaccurate reading of individual words and the fact that she performed well above chance in word/picture matching (as described in Bub, Black, Hampson, & Kertesz (1988).” Also, given that the authors accept MP’s verbaliza-

” Bub et al. (1988) proposed that MP’s relatively good word/picture matching was sup-


tions, like “Yes, that’s a word” (p. 28), as true indications of the stated meaning, we can safely assume that MP did have some lexical-semantic knowledge. A reported absence of semantic priming effects on MP’s reading latency also does not undermine this conclusion. Since it is not possible to ascertain what sort of semantic information might be preserved for a patient like MP, it cannot be assumed that the intact features of the semantic associates chosen would “prime” the target word. Finally, the abysmal performance on the PPVT by MP and other similar patients may only indicate that each of these patients had trouble selecting between semantically related foils. Thus, the accurate oral reading by each of these patients might have been supported by access to the Phonological Output Lexicon via partial semantic information along with information from the OPC mechanism. This hypothesis is schematically depicted in Fig. 2A.

Furthermore, it may be possible to explain performance by some of these patients, who supposedly read by the direct route, without appealing to either partial semantic information or direct connections between input and output lexical representations. MP is one such case. Bub et al. (1985) had assumed that reading of words such as very, bold and debt (all categorized by these authors as “exception” words) was only possible by direct whole-word correspondences. But each of these words would be pronounced correctly by applying the most common pronunciations of, respectively, v, e, r, y; b, o, 1, d; and d, e, bt (see Berndt et al. (1987) for these norms). The fact that there is no comparable explanation for correct reading of certain words, like yacht, island, aisle, coup, and corps, does not pose problems for this interpretation because MP failed to read any of these words correctly. Thus, cases such as MP do not, in fact, constitude evidence for the thesis that there must be direct, nonsemantic connections between input and output lexical representations. This pattern of performance is equally compatible within the summation hypothesis, assuming a severely damaged semantic system, but intact OPC procedures (Fig. 2B).

Besides the fact that these so-called “nonsemantic” readers might well have had some preserved semantic information (although perhaps not adequate to completely understand more than a few words), the reported data indicate that not one of these patients could have read onfy by direct lexical correspondences. The basis for this contention is the observation that each of the cases reported in the literature read regular words more

ported by access to the phonological representation directly from the picture, as well as from the word, but their evidence for such a conclusion is weak. They base their hypothesis on the finding that MP was better than chance at selecting the word that rhymed with the picture name. This performance could as easily be explained by assuming that partial semantic information accessed by the picture activated a number of phonological representations in the output lexicon, only one of which rhymed with one of the word choices given.

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accurately than irregular words and (for the patients in whom it was tested) read “mildly irregular” words more accurately than “very irregular” words. ‘* These patterns of reading performance would only be explicable in terms of a direct reading route by assuming two loci of impairment in these patients: the semantic component and the direct route or the Phono- logical Output Lexicon. WLP was the only patient who read irregular words well (95% correct), but her accuracy deteriorated to 71% (compared to 85% correct for regular words), along with further deterioration of semantics.

One hypothesis, offered by Shallice (1988) to account for these features of the patients’ reading, is that reading aloud involves a “broad” phonological route that includes orthography-to-phonology translation procedures for various sized units, including morphemes (see also Shallice & Mc- Carthy (1985)). So, they argue, regularity effects might result from loss of a subset of the spelling-to-sound correspondences, along with complete impairment of the semantic reading route. Although none of our data rule out such a hypothesis, the alternative proposed here, that reading can be accomplished by selecting a phonological representation in the output lexicon on the basis of incomplete information from both the semantic system and the OPC system, is equally consistent with the patients’ performance. Furthermore, the summation hypothesis more easily explains JJ’s mispronunciation of just those words for which he seemingly obtained no usable semantic information, as well as several of the patients’ apparently more accurate reading of irregular words (and correct pronunciation of homographic words) in reading meaningful narratives than of isolated words.13

Note that the summation hypothesis does not require that the patient be able to produce whole words via OPC procedures, only that the information provided by the OPC procedures be sufficient to “narrow down” the semantically related output representations activated by poorly specified semantic information. So, the hypothesis is not at odds with Funnell’s (1983) report of a “nonsemantic reader,” WB, who misread the 20 nonhomophonic nonwords presented to him, since most of WB’s responses, such as dreed -+ “deared” and cobe + “comb,” were very close to a correct pronunciation. In fact, if, as we have assumed along with Saffran (1985), the output of OPC procedures is referred to the Phonological Output Lexicon, we would actually predict this sort of lexicalization error.

‘* The only case who did not show the regularity effect is the Italian patient, Lisa (Sartori et al., 1987), who was not tested on irregular words, because nearly all words are regular in Italian.

I3 WLP (Schwartz et al., 1980), for example, like JJ, pronounced narrative fluently and accurately, even though she made errors on irregular words in reading word lists. MP reportedly read sentences rapidly and accurately, as well.


The summation hypothesis can also explain the reading performance by Lisa, a patient whose relatively spared reading of words in the presence of impaired semantics was interpreted by Sartori et al. (1987) as evidence for a direct reading route. On the basis of the observation that Lisa’s nonword reading was poor (16% correct) by comparison to her 80% correct word reading, Sartori et al. ruled out the possibility that she read via OPC procedures. Because these authors believed that Lisa also read without access to semantic information, they were forced to explain strong effects of concreteness on her reading and lexical decision performance as indications that concreteness, along with frequency and word class, is “represented” at the level of the Orthographic Input Lexicon. However, Lisa’s reading performance is also consistent with the summation account, since there is evidence that neither the semantic component nor the OPC procedure was completely nonfunctional. Thus, Lisa read 23% of four- letter nonwords correctly, indicating significant ability to convert gra- phemes-the probability of getting a phoneme correct given a grapheme was .7. The preserved partial functionality of Lisa’s semantic component was indicated by better than chance accuracy in identifying words as animals versus nonanimals and 70% accuracy in identifying words as abstract versus concrete. Her chance level of accuracy in word/picture matching tests cannot rule out partially preserved semantic information if the foils were semantically related (not reported). Thus, although the authors claimed that her performance provided evidence for proposing nonsemantic “addressing procedures” between input and output lexicons, their results can also be explained by assuming that partially impaired output from both the semantic system and OPC mechanisms combined to access entries in the Phonological Output Lexicon (Fig. 2C).

The proposed model of reading can also account for the frequent homophone confusions made by our patient PS, whose performance was similar to JJ’s with respect to the dissociation between impaired naming and comprehension versus spared reading and spelling, but opposite to JJ’s with respect to performance for animals versus nonanimals (Hillis & Car- amazza, in press, a, b). When PS attempted to read words aloud, he often “tried” a number of pronunciations until he happened to hit upon a word. This procedure, which resulted in a variety of possible candidates of varied degrees of orthophonological plausibility, often served him well even for reading irregular words. For example, he read sword as [swpd] . . . [sword] . . . “sword”. But if his pronunciation matched an incorrect word, he invariably understood the word as he pronounced it. For example, he incorrectly stressed the first syllable in reading exact and defined it as “not an act anymore”). Thus, he defined highly irregular words not as the incorrect homophone (e.g., heir defined as “air”) but as their “regularized” pronunciations (e.g., heir was read as “hare . . . in the kids’ story, two animals raced and one was a hare . the one that hops,”


and suite was defined as “what a man wears to church”). His comprehension of written homophones was very poor, even when he pronounced the homophones correctly-he assigned the most available meaning corresponding to the pronunciation, resulting in a homophone confusion about 50% of the time. Comprehension performance on this task was unaltered when he was instructed not to read the word aloud before defining it. The most plausible explanation for these results, which fits well with the patient’s subjective report, is that he “subvocalized” po- tential pronunciations, until he hit upon a real word. The phonological representation thus accessed served to access semantic information for comprehension. In other words, it is possible to explicate homophone confusions (in some patients) on the basis of OPC procedures that are capable of generating several alternative pronunciations of each stimulus, one of which activates a lexical-phonological representation and its associated meaning.

A similar account to that proposed for PS’s performance can also be offered for CD, a patient whose performance was interpreted by Coltheart et al. (1983) as providing evidence for direct access to the Phonological Output Lexicon from the Orthographic Input Lexicon, without semantic mediation. Coltheart et al. cite the fact that CD’s definitions of printed homophones without prior pronunciation of the words sometimes corresponded to homophonic words with different spellings (e.g., steak defined as “fencing post”) as evidence for the direct connections hypothesis. However, as in the case of PS, this result may reflect no more than the fact that the patient is able to generate multiple candidate pronunciations for a written stimulus through the application of POC procedures, which then serve to activate lexical-phonological and semantic representations. Consistent with this conclusion, CD’s definitions of irregular words, like those of PS, very often corresponded to regular pronunciations of the letter strings (e.g., bear + “a drink . . . beer”).

The evidence that has been cited in support of a nonsemantic, lexical route for spelling can also be accounted for by a summation hypothesis in which nonlexical spelling mechanisms (POC) interact with whatever semantic information is available, to activate entries in the Orthographic Output Lexicon. The patients who have been reported to have relatively accurate writing with impaired semantic information have all shown evidence of some (if not perfect) comprehension of spoken words. Many of these patients have also been shown to rely primarily on POC procedures for spelling words (see Baxter & Warrington (1987); Goodman & Car- amazza (1986a); Patterson & Shewell (1987)). An exceptional case, Michel (Kremin, 1987), demonstrated impaired, but certainly not abolished, POC procedures. But consistent with our hypothesis, he correctly spelled 83% of words he claimed to understand perfectly and only 35% of words he claimed to understand “a bit, but not quite” (Kremin, 1987, p. 316).


Kremin’s claim that Michel spelled by nonsemantic, lexical means was based on a test in which the patient was asked to make a yes/no decision about comprehension as he wrote the word. He responded with “no” to more than half of the words, many of which he spelled correctly. But certainly, his negative response regarding comprehension does not rule out partial semantic information, especially since he so rarely claimed to have “no idea” of the meaning of words when given this option on other tests. Hence, Michel’s pattern of performance is explicable within the summation hypothesis by proposing partial damage to the semantic system and to the POC mechanism (a spelling version of Fig. 2C).

The performance of Patterson’s (1986) patient GE can also be explained by the summation hypothesis. This patient demonstrated relatively good comprehension of words that he could not spell in written naming tasks but could spell (fairly well) to dictation. Further, GE was impaired, but not completely incapable, of using POC procedures; he wrote letters corresponding to letter sounds with 86% accuracy and spelled simple nonwords with 34% accuracy. Thus, although his ability to use POC procedures would not have been sufficient for producing very many regular words entirely without error or for producing a substantial number of phonologically plausible errors, it could have been sufficient to contribute just enough activation to target lexical representations in the Orthographic Output Lexicon (already partially activated by the semantic system) to help them surpass threshold for output. In fact, GE’s performance con- forms with the expectations we would derive if we were to assume (1) that he had damage to the Orthographic Output Lexicon (such that representations have raised thresholds of activation or are otherwise less accessible) and (2) that he was partially impaired in the use of POC procedures (as would be illustrated by a spelling version of Fig. 2E). Also consistent with the hypothesis that he relied on activation from the semantic system, along with imperfect input from POC mechanisms, is the fact that GE rarely made homophone confusions in spelling to dictation. l4

Reports that some patients produce correctly spelled, but contextually inappropriate, homophones to dictation (Roeltgen, et al., 1986) are not inconsistent with the summation account. Roeltgen et al. (1986) reported five patients who, given a sentence such as “Spell /nat/ as in ‘He is not here’ ” (p. 263), occasionally wrote the wrong homophone (knot in this example), but spelled it correctly. Because semantic information could

I4 To explain these results within the hypothesis of a “nonsemantic route” for spelling, Patterson proposed (1) feedback mechanisms between the semantic system and the phonological input lexicon and (2) direct connections between meaning-specific phonological representations (e.g., an independent representation of /per/ for “pear” vs. /per/ for “pair”) in the input lexicon and corresponding meaning-specific phonological representation in the output lexicon.


not have activated the lexical representation of knot in this case, and because the POC mechanism would be unlikely to generate an irregular spelling such as knot, the authors argued that these results provide evidence for a direct, nonsemantic lexical route for spelling. (The proportion of correct spelling of irregular, semantically incorrect homophones was not reported, but each patient produced at least one example). Although these data are consistent with the direct route hypothesis, they are also consistent with the hypothesis that orthographic representations of irregular homophones were activated by the output from the POC mechanism when no semantic information was available to activate the correct lexical entry. To account for these results, we must assume that (1) semantic information that would normally activate the correct homophone was impaired, and (2) the patients had some use of sublexical POC mechanisms. In fact, Roeltgen et al. document both of these conditions: Each of their patients demonstrated difficulty comprehending the homophones or the sentences in which they were dictated, and each was able to spell nonwords relatively well. Also consistent with the summation account is the fact that semantically incorrect homophone responses were less likely than semantically correct homophone responses. Further, for each patient in whom it was tested, the frequency of correctly spelled, semantically incorrect homophones dropped considerably (e.g., from 45 to 12% of responses) when the patient was shown a picture corresponding to the meaning of the target homophone, indicating that semantic information played a crucial role in these patients’ spelling performance. In summary, then, there does not seem to be any clear case of accurate spelling or reading of irregular words without at least some knowledge of orthography-to-phonology correspondence or at least some semantic information.

CONCLUSION

The available evidence does not require that we assume the existence of nonsemantic procedures for accessing lexical phonology directly from lexical-orthographic representations in reading. The very same conclusion can be drawn with respect to the “direct” spelling route. Thus, it has been possible to account for the data cited as evidence for direct route models by proposing an alternative set of assumptions about the processing structure of the reading and spelling systems-the summation hypothesis.15,1”

” It is also possible that an additional, direct route might operate in conjunction with partial semantic information-i.e., that both proposals are correct. We discuss the “summation account” alone, without assuming a direct route, only because this account allows us to explicate JJ’s pattern of performance by postulating only one level of impairment in the reading process, whereas the alternative proposals would necessitate postulating at least two loci of damage (to the direct route and the semantic system) for JJ.

I6 Still another alternative explanation of the data is that semantic information and sublexical phonological or orthographic information come together at a postlexical level, say,


Although both the direct route and the summation hypothesis can be fleshed out in such a way that each can be made consistent with the available experimental results, there may be reasons to prefer the latter account. Several findings from the case we have reported and from other cases follow more “naturally” from the summation hypothesis than the direct route account. Take, for example, the production of phonologically plausible errors, particularly in response to abstract, irregular words, by JJ and each of the other so-called “nonsemantic” readers. To account for these errors, the direct route hypothesis would have to assume at least two levels of impairment in the lexical system: the semantic component and the Phonological Output Lexicon or the direct route to it. In contrast, the summation hypothesis explains this pattern of performance by proposing a single locus of damage, to the semantic component, which may differentially affect individual items or classes of items (say, abstract words), such that information may be “abolished” for certain items (leav- ing only OPC procedures to support reading aloud), partially preserved for other items, and fully spared for still others. Furthermore, unlike the direct route hypothesis, the summation hypothesis directly predicted JJ’s reported pattern of reading as a function of both comprehension and orthophonological regularity. Here, again, the direct route hypothesis is not ruled out by the data we have reported, but does not offer a motivated account for them either. In light of these considerations, it would seem that the summation hypothesis provides a better account of the available evidence than the direct route hypothesis.

There are a number of other patterns of performance that we would expect to result from various loci of damage to a functional architecture of the reading system in which OPC mechanisms and the semantic component both contribute to activation of the phonological representations in the Phonological Output Lexicon (as depicted in Fig. 2). To begin with, when OPC procedures are totally abolished, oral naming and oral reading performance should be essentially identical. A number of such cases have been reported. For example, we reported two patients, RGB (Caramazza & Hillis, 1990) and KE (Hillis, et al., 1990), who were not able to read or spell any nonword, nor were they able to produce sounds corresponding to individual letters, or vice versa.17 This pattern of per-

a response buffer. In this case, if an incorrect lexical representation were to be activated by impaired semantic information, it would be “rejected” at the level of the response buffer if it conflicted with whatever phonological information about the word had been assembled. However, this explanation would require us to explain how an alternative entry in the output lexicon is activated, once the first representation is rejected. It does not seem likely that, in the course of fluent reading, each rejection from the response buffer requires the process of reading the word to “begin again” repeatedly, until the activated lexical entry is compatible with the assembled phonological information in the response buffer.

I’ KE correctly read a few nonwords that were both visually similar and homophonic to


formance suggests that sublexical OPC and POC mechanisms were not available to either patient for reading or spelling to dictation. Each patient made frequent semantic errors in oral tasks, at comparable rates in reading and oral naming. Because RGB made no semantic errors in written naming, spelling to dictation, or comprehension, it was hypothesized that his reading performance reflected selective damage within the lexical system to the Phonological Output Lexicon, along with damage to sublexical POC and OPC procedures (Fig. 2F). KE, on the other hand, showed comparable error rates and essentially the same category differences across oral and written naming, comprehension, oral reading, and spelling to dictation. This modality-independent lexical performance was interpreted as evidence for selective impairment to the one processing mechanism showed by all of the affected tasks-the semantic component. Thus, the production of semantic errors by KE could be explained by assuming a disruption of sublexical mechanisms, along with a single locus of impairment in the lexical system-the semantic component in this case (Fig. 2D). (Because KE was able to repeat nonwords, his successful repetition of all categories of words was assumed to reflect the operation of nonlexical auditory to phonology to articulatory processes.)

Now, if we had assumed that there were direct routes between input and output lexicons, we would have been forced to propose that KE had two additional loci of damage in the lexical system, to both direct routes, since his oral reading and spelling to dictation were as impaired as his naming and comprehension. We would then have had to assume either that damage somehow affected all categories to essentially the same degree in each of the direct lexical routes and in the semantic system or that both direct routes were virtually abolished, despite preserved functioning of both input and output lexicons. Thus, an explanation of KE’s performance within the direct route account is not impossible, but requires additional assumptions not needed by the summation account.

The proposal we have outlined also leads us to expect a dissociation between oral naming and oral reading (and/or between written naming and spelling to dictation) when there is damage to the output lexicon(s) or to the semantic system in the presence of at least partially preserved sublexical conversion procedures. These sorts of cases have also been described. A number of examples, cited earlier, have been reported as evidence for the direct route hypothesis, but we were also able to account for their patterns of performance by assuming partially impaired semantics and intact or partially impaired sublexical procedures. In addition, at least two cases for whom there is information regarding performance in all of the relevant lexical tasks can be explained by assuming intact semantics

real words (e.g., skurt). We assume that the nonwords in this case activated visually similar real words in the Orthographic Input Lexicon, which were then processed as words.


but partial impairment to one or both output lexicons, which was overcome in oral reading by at least partially preserved sublexical mechanisms.

Miceli, Guistolisi, and Caramazza (in press) reported a patient, SF, who had normal performance in oral reading, spelling to dictation, and comprehension, contrasted with very poor oral and written naming, particularly of low frequency words. Although he was unimpaired in reading and spelling nonwords, his disproportionately high level of performance in oral reading and spelling cannot be attributed only to sublexical reading and spelling, since he was able to read and spell irregular low frequency words. Thus, we must assume that in reading low frequency words, SF was able to access lexical-phonological information, perhaps because of the additional phonological information contributed by the OPC procedures (Fig. 2G). Because the latter information is not available in naming tasks, SF’s performance was predictably impaired in these tasks.

Another patient we have studied, RXB, showed disproportionately impaired oral naming (57% correct) compared to written naming (87% correct), oral reading (94% correct), and reading comprehension (99% correct) with the same 144 items. Although RXB correctly read 6/34 pseudohomophones ( e.g., lemmun, cherch), he was unable to read any nonhomophonic nonword accurately. However, his responses to nonwords were usually close to a correct response (e.g., wundoe + /wmda/, rhyming with “Linda”), suggesting that he had some use of OPC procedures. Furthermore, his most frequent types of errors on nonwords were lexi- calizations (e.g., boke + “boat, bloke”; sarcle -+ “sergeant, sarge”), consistent with the hypothesis that the partial information generated by his impaired OPC procedures was used to activate a lexical-phonological representation. Thus, his accurate reading of words that he understood (but could not name in response to pictures) can be plausibly explained by proposing that activation of relatively inaccessible entries in the Phono- logical Output Lexicon by intact semantic information was augmented by partial information from OPC mechanisms in the reading process (Fig. 2E). Since the latter source of information would not be available to facilitate naming in response to pictures, oral naming was predictably poorer than reading.

Each of the patterns of performance, which would follow from proposing different deficits within a model of reading that assumes summation of semantic information and phonological information from OPC procedures, is summarized in Fig. 2. None of these patterns rules out the existence of a direct reading route, but neither are they specifically predicted by the direct route hypothesis. One pattern of performance that would provide evidence for such a direct route is accurate oral reading in the face of impaired semantics and total inability to use OPC procedures (as might be indicated, say, by unrelated responses in reading nonwords and by an absence of a regularity effect in reading words). The summation


account would predict poor reading in this case, as illustrated in Fig. 2H. Correct reading in the absence of both semantics and OPC procedures, which to our knowledge has not been described, would not, however, rule out the hypothesis that information from intact sublexical procedures (in other patients) summates with semantic information in accessing lexical representations for output.

In short, then, not only is the summation hypothesis able to account for detailed aspects of JJ’s performance, but it is also able to provide a good fit for other patterns of performance previously assumed to provide evidence for the direct route model of reading (and spelling). Further- more, although the reported data do not rule out the direct route model of reading, neither are they readily predicted by such an account.

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