Independence of Input and Output Phonology in Word ...sla.sjtu.edu.cn/thesis/independence of input...

Journal of Memory and Language41, 3–29 (1999)Article ID jmla.1999.2637, available online at http://www.idealibrary.com on

Independence of Input and Output Phonology inWord Processing and Short-Term Memory

Randi C. Martin, Mary F. Lesch, and Michael C. Bartha

Rice University

Recently, theorists have suggested a close relation between the codes activated during languageprocessing and those involved in STM. In order to further investigate this relationship, we examinedthe performance of an anomic patient, MS, to determine whether he would exhibit the sameimpairment in retrieving phonology from semantics in short-term memory that he shows in picturenaming. The results indicated a similar pattern of performance in naming and in STM tasks requiringretention of output phonological codes (those involved in production). However, MS performed at ahigh level on STM tasks requiring the retention of input phonological codes (those involved inperception). The findings support the following conclusions: semantic information contributes toSTM, input and output phonological codes are separable and maintained in separate buffers, and thesame pathway that underlies retrieval of phonology from semantics in naming underlies feedbackfrom semantics in list recall. © 1999 Academic Press

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In contrast to earlier models of short-tememory (STM) which have focused solelythe role of phonological and/or articulatocodes (e.g., Baddeley, 1986), more recentceptions of short-term memory also incorpoa role for lexical and semantic representatioThese “language-based” models of STM hemphasized the close relation between theresentations and processes involved in wperception and production and those involveshort-term memory (Martin & Lesch, 199Martin, Shelton, & Yaffee, 1994; Martin & Romani, 1994; N. Martin & Saffran, 1992, 199N. Martin, Saffran, & Dell, 1996). The purpoof the present study was twofold: (a) to invtigate the relation between word perceptionproduction and short-term memory and (b)investigate the possible distinction between

This research was supported by NIH DCD GrDC00218 to Rice University. We thank MS for all the tiand effort that he has given to this project and his familytheir cooperation. Michael C. Bartha is now at the CognNeuroscience Laboratory, Baylor College of MedicHouston, Texas.

Correspondence concerning this article should bedressed to Randi C. Martin, Psychology Department -25, Rice University, 6100 Main Street, Houston, Te77005-1892. Electronic correspondence may be se
[email protected].
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phonological codes involved in perception aproduction.

CONCEPTIONS OF WORD PRODUCTIONAND COMPREHENSION

In order to lay out the relationship betweword processing and short-term memory, inecessary to consider current conceptuations of the representations and processevolved in word production and comprehens(see Fig. 1). In production, the speaker bewith a concept to be conveyed which is encosemantically. The semantic representationused to select a lexical representation to conthe intended concept and then this lexicalresentation must be encoded phonologicprior to the onset of articulation. In spoken wocomprehension, the reverse sequence ocAcoustic information is translated into a phological representation which encodes phonidentity and order. This phonological represtation then activates a lexical representawhich is connected to semantic information cresponding to that word.

It should be noted that in the language pduction and comprehension literature, therconsiderable debate concerning the nature o

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4 MARTIN, LESCH, AND BARTHA

Levelt, 1989) assume that lexical represetions contain lexical semantic features (whare distinguished from conceptual semantictures) as well as syntactic information, suchword class, subcategorization frame, and grmatical gender (for languages where genderelevant). Other researchers (e.g., Levelt,elofs, & Meyer, in press) make no distinctibetween conceptual and lexical semantics (are represented at the semantic level) andsume that the lexical representation contonly syntactic information. Finally, other rsearchers (e.g., Dell, Schwartz, Martin, Saff& Gagnon, 1997) assume that the lexical nis essentially empty and serves only as a plholder to connect all the information (phonlogical, semantic, syntactic, graphemic) tpertains to a particular word (for yet anotposition, see Miozzo & Caramazza, 1997)the present discussion, we will take the laview.

FIG. 1. Levels of representation in speech perceptionroduction.

Interactive activation models such as the

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TRACE model of word perception (McClella& Elman, 1986) and the speech productmodel proposed by Dell (1986; DellO’Seaghdha, 1992) incorporate these diffelevels of representations and assume feeward and feedback connections between leFor example, in Dell and O’Seaghdha’s (19model of speech production (Fig. 2), semafeatures are connected to lexical represetions, which are connected to phonemes. Avation flows through the network in responseactivation at the semantic level. For examsuppose that the production task involvesture naming and the object to be named“lion.” The process of picture recognitiowould lead to the activation of semantic featuof the pictured object. Activation of thesemantic features would result in a spreadactivation from the semantic level to the lexilevel, and the appropriate lexical node wobecome most activated. However, there woalso be weaker activation of other lexical rresentations that share semantic featurestiger, cat). Activation of these lexical represtations would lead to activation of the tarword’s constituent phonemes and to weak avation of the constituent phonemes of themantically related words. The model alsocludes feedback from the lexical to the semalevel and from the phoneme to the lexical levThus, since the lexical node for “lion” will bmost activated from the semantic input, feback from the lexical node to the semantic lewill tend to reinforce activation of the approp

FIG. 2. Dell & O’Seaghdha’s (1992) model of spee

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5INDEPENDENCE OF INPUT

ate semantic features. Similarly, since the pnemes of “lion” will be the most activatefeedback from the phoneme nodes will reforce activation of the appropriate lexical noHowever, some inappropriate nodes will betivated from feedback as well, but to a lesdegree. Thus, the partial activation of the lexnode for “tiger” would feed activation back tosemantic feature for “has stripes,” and the avation of the phonemes for “lion” will causlexical nodes with similar constituent phonem(e.g., “line”) to receive some degree of actition.

An issue that arises when considering moof language processing is whether the phological forms involved in perception and pduction are different. Some models of speperception and speech production implicitlysume a separation of input and output phological forms. For example, the modular moof speech production proposed by RoelMeyer, and Levelt (1996; see also LevRoelofs, & Meyer, in press) assumes thaword production a single lexical semantic/stactic representation (termed “lemma”) is csen prior to access to a lexical phonologrepresentation (termed “lexeme”). In this mothere is no feedback from the lexeme levethe lemma level. In order to avoid such feback, it is necessary to assume a separbetween input and output phonological formsthey were one and the same, then activatiothe lexemic representation should lead to amatic spread of activation back to the lemlevel.

A number of other theorists have arguedthe basis of neuropsychological studies andperimental studies with normal subjects thatphonological forms involved in perception aproduction are different (e.g., Howard & Franlin, 1990; Monsell, 1987; Shallice, McLeod,Lewis, 1985). For example, Shallice et(1985) demonstrated that there was relatilittle interference between reading words al(processing output phonology), and detectinspecific name in a speech stream (procesinput phonology) whereas there was masinterference between shadowing one mes
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processing input phonology). If there are serate input and output phonological forms, thewould seem to follow that the forms usedperception are more closely related to acouspecifications, whereas the forms used induction are more closely related to articulatspecifications. For example, Jusczyk’s (19model of speech perception assumes that actic features are abstracted from the inputweighted according to their importancemaking distinctions in that language. Onproduction side, Levelt (1989) suggestedsyllable size units are used in productionthese consist of the articulatory phonetic ftures for each syllable.

RELATION BETWEEN LANGUAGEPROCESSING AND SHORT-TERM

MEMORY

Our conception of the theoretical underpnings of memory span performance assuthat there is a direct relation between the resentations and processes involved in wordception and production and those involvedshort-term memory. Thus, according to ourproach phonological, lexical, and semantic rresentations are activated in both languagecessing as well as in verbal short-term memWe further assume that: (1) all levels of repsentation in short-term memory depend onactivation of long-term representations witsemantic memory (the knowledge store forformation about words) and (2) these repretations are activated at encoding and this avation is maintained during retention.

Two different possible instantiations of thapproach are shown in Fig. 3. In Fig. 3a, this one short-term memory buffer into whichthe levels of representation for each lexical iare copied. This approach bears some similto the programmable blackboard model ofsual working memory presented by McClella(1986). In Fig. 3b, there are separate buffersphonemic and lexical–semantic representatiThis approach is similar to the model presenby Barnard (1985) for verbal short-term meory. In either approach, we assume thatlong-term knowledge store for verbal inform
etion (on the left side) is connected to the buffers

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such that activated information from the knoedge store continues to activate informationthe buffers and the activated information inbuffers feeds back to keep the representatiolong-term knowledge store activated. It mseem redundant to assume both persistingvation in the long-term knowledge store andexistence of storage buffers. However, it isclear how persisting activation in the long-testore could serve to represent list informtion—in particular, how such activation coube used to differentiate repetitions of the saitem in a list (e.g., a list such as “chair leaf ch

FIG. 3. Models of short-term memory incorporaOne buffer containing interactive representationsknowledge store.

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the model in Fig. 3b over that in 3a. First,presence of several representations in the sbuffer, as in Fig. 3a, would seem to suggestthese representations could interact, but it isclear that such an assumption is necessary.ond, the separation of the buffers providemore natural means of accounting for the setive impairment in phonological or lexicasemantic retention that has been uncoverebrain-damaged patients (e.g., Martin et1994, see below for further discussion). Ththere are data from animal studies indicathat separate areas of the brain are involve

separate lexical–semantic and phonological buffers.) Separate buffers with interactions only in the long-te

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ject (such as shape vs. location) over a d(Wilson, Scalaidhe, & Goldman-Rakic, 199There are also some neuroimaging data fhumans suggesting separate brain areavolved in working memory for spatial vs. objeinformation, though so far there has been aof consistency in the anatomical localizationthese areas across studies (e.g., Baker, FFrackowiak, & Dolan, 1996; Smith, JonidKoeppe, Awh, Schumacher, & Minoshim1995). Thus, these findings suggest that dient brain areas are involved in the maintenaof different types of information pertainingthe same stimulus, and those brain areasvolved in maintenance differ from the areinvolved in the primary processing of thetypes of information.

Rather than assuming that the different leof representation in the short-term membuffer can interact, we assume, as in DellO’Seaghdha’s (1992) model and the relatedproach to short-term memory presented byMartin and Saffran (1992, 1997), that represtations in theknowledge structurecontinue tointeract after an item has been presentedthat there is feedforward and feedback of avation between the different levels. Since avation in the knowledge structure at differlevels serves to activate the representationthe buffers, the contents of the buffer(s) wreflect the interactions in the knowledge strture. For instance, if high frequency items hstronger lexical activations in the knowledstructure, then high frequency items will tendhave higher activations in the buffer. For wolist recall, lexical representations in the bufare selected for output. For nonword list recactivation of buffered representations atphonemic level will be used for recall.

According to our approach, if the representions or processes involved in word percepand production are damaged, then short-tmemory will be affected as well, with predicable consequences depending on the partirepresentation or process that is affected.example, if semantic representations are daged, then feedback from the semantic tolexical level will be minimal in the knowledg
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cal–semantic representations in the bufferbe reduced. Consequently, the normal adtage of word over nonword list recall (Bren1940; Crowder, 1978; Hulme, Maughan,Brown, 1991; see below for further discussiwill be reduced. We have also argued thatpossible for word perception and productionbe preserved, but for the buffer to be affecsuch that patients might show overly rapidcay of representations at a particular levegreater than normal effects of interference frother items in the to-be-recalled list.

EVIDENCE FOR MULTIPLE LEVELS OFREPRESENTATION IN SHORT-TERM

MEMORY

honological Representations

Language-based models of STM suggesmportance of multiple levels of representati.e., phonological, lexical, semantic, syntacthe contribution of phonological represen

ions to verbal short-term memory is well domented, and many models of short-term mry have dealt primarily with accounting fhonological effects (e.g., Baddeley, 1986; Bess & Hitch, 1996; Houghton, Hartley,lasspool, 1996). Effects of phonological s

larity have been taken as evidence for the pological nature of the short-term store (ConHull, 1964; Hintzman, 1965; Luce, FeustPisoni, 1983; Schweickert, Guentert, & He

erger, 1990; Sperling & Speelman, 19ickelgren, 1966) and word length effects h

een taken as evidence for an articulatoryearsal process (Baddeley, Thomsonuchanan, 1975; Mackworth, 1963; Schwert & Boruff, 1986; Schweickert et al., 199ecently, others have argued that word lenffects do not necessarily implicate rehearut instead reflect the greater number of pho

ogical segments in longer words (Brownulme, 1995; Neath and Nairne, 1995; Serv998).An issue separate from whether phonolog

epresentations are maintained in STMhether there are separate retention capa

or input and output phonological forms.
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cessing assume such a separation. A typprocedure in standard short-term memory pdigms involves presenting a list of words autorily and having the subject reproduce theorally. Thus, both word perception and woproduction are involved. Thus, it is plausithat there are separate capacities for maintainput and output forms. If a separation betwinput and output phonology exists, thenmodel in Fig. 3b would need to be revisedshown in Fig. 4 to include separate capacfor maintaining input and output forms. On tword processing side there is a direct conntion between input and output forms (thatthat doesn’t go through lexical and semaforms). The ability to repeat nonwords is edence for the existence of this connection.ther through learning or possibly through soinnate endowment, humans can take an iacoustic form and come up with the articulatform needed to reproduce it. The connectiothe opposite direction reflects the ability to

FIG. 4. Model of short-term memory incorporatin3b, interactions occur only in the long-term know

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without involving audible speech productioThat is, one can imagine the sound of a wornonword even when the word or nonword mibe pronounced internally. Some have suggethat the recirculation between input and ouforms constitutes inner rehearsal (see HowaFranklin, 1990; Martin, Blossom-Stach, Yaff& Wetzel, 1995; Monsell, 1987).

With regard to separable STM capacitiesretaining input and output forms, there are nropsychological data that bear on the issHoward and Franklin (1988, 1990) have argfor a model in which there are separate inand output phonological stores and a reheaprocess which circulates information betwinput and output forms (see Monsell, 1987,a related proposal). Part of their evidence cofrom a patient, MK, who showed good perfmance on matching span tasks and good spproduction, but severely impaired single wand nonword repetition. (In a matching sptask, the patient has to say whether two lists

eparate input and output phonological buffers. As in Fie store.

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not required, matching span is presumed toflect the retention of input phonological repsentations.) They argued that MK had preseinput and output stores but a disruption inprocesses which convert between input andput forms. Other evidence comes from Allpo(1984) study which contrasted two brain-daaged patients, both of whom showed veryduced memory span on repetition tasks.two patients differed, however, in their perfmance on a matching span task. One paperformed as poorly on the matching spanas on the list repetition tasks, whereas the oshowed excellent performance on the matcspan task, at least for three- and four-word lAllport argued that the two patients differedthat one had a disruption of an input phonolical store, whereas the other had a preservaof the input phonological store, but a disruptof the output phonological store. Romani (19has presented more recent evidence of awho appeared to have a preserved input phlogical store and disrupted output phonologstore as the patient performed very wellmatching span and probe tasks for even nword lists, but performed poorly on list repetion.

Other patients provide evidence of a dissation opposite to that presented by Rom(1992). Patient EA reported by Martin et(1994) and patient JB reported by ShalliceButterworth (1977) did very poorly on matcing span and memory probe tasks (whichdo not require list output), thus implying a druption of the input phonological store. Hoever, their spontaneous output was normaassessed by a variety of measures incluspeech rate, syntactic complexity, pausing,Assuming that spontaneous speech produinvolves planning several phonological forsimultaneously, their preserved production sgests a preserved output phonological store

In evaluating these neuropsychological dit is necessary to take care to distinguwhether the evidence strongly supports thesumption of separate input and output phological codes and input and output storeswhether a model which assumes separate
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logical representation and semantics couldcommodate the data (see Shallice, 1988,discussion). Thus, for example, if a patientgood spoken word comprehension but poorduction, one would not need to postulate serate input and output phonological forms, asdifficulty might be in the output pathway factivating phonology from lexical and semanrepresentations. However, some of the cdiscussed above present a challenge to thegle phonological representation account.example, patient EA (Martin & Breedin, 199Martin et al., 1994), who was argued to haveinput store deficit, showed excellent comphension of single words, and it would thusdifficult to argue that disruption of the inppathway from phonology to semantics coaccount for her severe deficit on input STtasks. Similarly, the patient reported by Rom(1992), who was argued to have an output sdeficit, was good at producing single wordsnames of pictures and in repeating single woand thus disruption of the output pathway frsemantics to phonology seems an unlikelycount of his output store difficulties.

One source of evidence that seemed to astrongly for the separation between inputoutput phonology came from cases of deepphasia (see Howard & Franklin, 1988, foreview). These patients have difficulty repeanonwords and make semantic errors in theetition of single words (e.g., saying “mirror”response to “reflection”). They also showfects of imageability on word repetition, wibetter success at repeating high imageabwords. The patients’ semantic errors sugthat phonological perception proceeded arately—otherwise, why would they accesssemantically related word? If input and outphonological forms were the same, one wothen expect these patients to be able to prothe phonological form that they had perceivTheir production of a semantically related worather than the correct word, suggests thatinput form cannot be used for production athat they had some type of difficulty in retrieing the output form (because of either degrasemantic representations or output phonolog
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them). This pattern of symptoms could not eily be accounted for in terms of separate pways from semantics to phonology on the inand output sides, but one phonological resentation. Even if output links from semantto phonology were damaged, the patient shstill be able to produce the phonological foperceived on the input side if the input aoutput forms were the same.

Even though the evidence from deep dyspsia may seem to provide compelling supporta separation between input and output phoogy, N. Martin and Saffran (1992) have pposed an account of these symptoms usinginteractive activation model, which is closerelated to Dell’s (1986; Dell & O’Seaghdh1992) model of speech production. In ordeaccount for repetition, the model is assumework in the opposite direction as well, that isperception as well as in production. Theirproach does not assume a separation betinput and output phonological forms in accouing for deep dysphasia. Instead, they assthat deep dysphasic patients suffer from a rloss of activation at the phonological, lexicand semantic levels. Since the phonologicalresentation derived from perception of the indecays very rapidly, it is not available atmoment of production and has to be recontuted from semantics. Decay at the lexicalsemantic levels results in semantic errors (other error types) in repetition.1

Recently, however, Dell, Schwartz, MartSaffran, and Gagnon (1997) encountered dculties when they attempted to model bothword production and word repetition patternsaphasic speakers with this model. They fothat the parameters needed to account fortients’ accuracy and error patterns in produccould not reproduce their repetition patternsmodel repetition more accurately, it was necsary to assume that perception was entirely

1 Howard and Franklin’s patient MK made semanticors in repetition and showed very poor nonword repetihus, he would fit the clinical designation of deep dysphK’s good performance on tasks tapping the retentio

nput phonological forms argues against N. Martinaffran’s (1992) account of deep dysphasia as a ge
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curate for most patients. In order to capturedifference between perception and producin their model, there has to be some separabetween input and output phonological pcesses. They leave as an open question theof exactly where this differentiation occurs.

Lexical and Semantic Representations

With regard to the involvement of lexical asemantic codes in short-term memory, findifrom both normal and brain-damaged patiesupport this assumption. For example, stuof normal subjects have demonstratedmemory span is greater for words than nwords (Brener, 1940; Crowder, 1978) evwhen controlling for pronunciation rate for ttwo types of materials (Hulme, Maughan,Brown, 1991). Thus, there is a lexical contribtion to span that appears to be independenthe functioning of the articulatory loop (but sMulthaup, Balota, & Cowan, 1996). Alsmemory span is greater for high than low fquency words (Gregg, Freedman, & Sm1989; Roodenrys, Hulme, Alban, Ellis,Brown, 1994; Tehan & Humphreys, 198Watkins, 1977), greater for words drawn frthe same semantic category than for wodrawn from disparate categories (Poirier &Aubin, 1995), and greater for high than for limageability words (Bourassa & Besner, 199

Findings from neuropsychological studies sport the conclusion that not only are semanticphonological information retained in STM, butcapacities for retaining the two types of informtion are separable. These studies have destrated that dissociations may be obtained betwpatients’ ability to retain phonological and semtic information. These dissociations have bdocumented by examining the effects of phological and lexical/semantic variables on spanby examining serial position effects and errorterns. For example, Martin et al. (1994) repothat patient EA failed to show normal effectsphonological similarity and word length on meory span, but showed a normal advantage in mory span for words over nonwords and performbetter on a category probe task than on a rhprobe task. Patient AB showed the reverse pa

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and nonword span, and better performancerhyme probe than category probe task. Anopatient, ML, has recently been documentedshow a pattern similar to that of AB (MartinLesch, 1996). Importantly, patients AB and Mperform at high levels on tasks that assessintegrity of semantic information (MartinLesch, 1996). Thus, it is the short-term retenof semantic information that is impaired andsemantic knowledge itself. Based on these dMartin and colleagues (Martin & Lesch, 199Martin & Romani, 1994; Martin et al., 199propose that the capacities for the short-termtention of semantic and phonological informatare separable.

Additional neuropsychological evidencethe involvement of lexical and semantic cocomes from the work of Patterson and cleagues and of N. Martin and Saffran. PatterGraham, and Hodges (1994) and Knott, Pason, and Hodges (in press) have demonstrthat patients with dementia that affects semarepresentations show a larger word spanknown words than for unknown words (thatwords for which they no longer know the meing). Saffran and N. Martin (1990; MartinSaffran, 1992, 1997) have analyzed the wprocessing and short-term memory deficitspatients with phonological vs. semantic pcessing deficits and found distinctive short-tememory patterns with regard to recencyprimacy effects in serial recall and the effectsimageability and frequency at early vs. laterial positions. That is, patients with phonolocal processing deficits tend to show greatermacy than recency effects and greater effecimageability at late serial positions, wherpatients with semantic processing deficits tto show greater recency than primacy effeand large effects of imageability at earlypositions. Thus, there is evidence from bnormals and brain-damaged patients suppothe involvement of multiple linguistic codesverbal short-term memory.

GOALS OF THE CURRENTINVESTIGATION

The present study investigated the rela
between word perception and production an
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short-term memory and the possible distincbetween input and output phonology by exaining the performance of MS, an anomictient—that is, a brain-damaged individual wa severe and selective deficit in naming.cording to the models shown in Figs. 1 andnaming deficit could result from a breakdownany point in the process going from semanticarticulation (including, for example, disruptsemantic representations or a disruption of cnections between lexical and phonemic resentations). For MS, we will present evidethat semantic and lexical levels are preseand that his difficulty is in activating a phonlogical representation.

According to the models shown in Figs. 3 a4, a disruption of the connection between lecal and phonological representations in speproduction should affect short-term memosince the same representations and connecbetween representations are involved in feeactivation into the short-term memory buffMoreover, to the extent that the naming deis specific to certain items or types of itemthen short-term memory for those items shoalso be impaired.

The proposed distinction between inputoutput phonological capacities (see Fig. 4also relevant to the analysis of MS’s short-tememory performance. The contrast betweenpreserved comprehension and his very impanaming suggests that input phonology, semtics, and the connections between them areserved even though the connections betwlexical representations and output phonolare disrupted. Thus, to the extent that inputoutput phonological representations are disguished in short-term memory, one would pdict that MS would perform poorly on tastapping the retention of output phonologicodes, but might perform well on tasks tappthe retention of input phonological codes.

PATIENT DESCRIPTION

MS is a 30-year-old, right-handed male w2 years of college education. He contractedpes encephalitis in 1993 which resulted inimpairment of language abilities together wit
dsparing of most other cognitive abilities. An

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MRI scan and an EEG recording suggestedtemporal damage. The testing reported htook place between 6 months and 3 years ponset. MS displays a pattern of surface dysland dysgraphia on single word reading and wing tasks. That is, he reads and spells reguspelled words (e.g., belt) much better thanregular words (e.g., sword) and tends to mregularization errors in reading and spell(e.g., reading “yacht” as /yækt/ and spell“pheasant” as “fezent”). On the word lists frothe Psycholinguistic Assessments of LanguProcessing in Aphasia (PALPA) (Kay, Less& Coltheart, 1992), MS obtained a mean93% correct (across two testing sessionsreading regular words, but only 52% correcreading irregular words. Because of his difficties with reading and spelling, the current invtigation probed his abilities with tasks that uauditory presentation and oral responses.tions of these data were presented previousMartin and Lesch (1996).

WORD PRODUCTION ANDCOMPREHENSION

The tests reported below examined MS’sle word production and comprehension. Th

ests were administered in order to exploreature of MS’s naming difficulty. Anomia maave multiple causes. For example, a paay have difficulty naming pictures because

emantic representations corresponding toepicted objects have been damaged (Wington, 1975; Howard & Orchard-Lisle, 198r because the phonological representationertain words have been disrupted (see Elloung, 1988) or because the patient has dulty activating a phonological representatrom an intact lexical–semantic representaKay & Ellis, 1987). The following tests weesigned to provide a rigorous assessmenS’s semantic knowledge in order to rule ou

emantic impairment as the cause of his ano

ord Production

Naming.MS obtained a score of 10 on t0-item Boston Naming Test (Kaplan, Goolass, & Weintraub, 1983), indicating a sev

mpairment in naming ability (control mean5

ftet-a-ly-e

e,

n

-

r-n

-ee

teer-

r

-

of

a.

5.86, SD5 2.86, Kaplan et al., 1983). MS wlso tested on the Philadelphia Naming TRoach, Schwartz, Martin, Grewal, & Brech996), which consists of 175 items with namarying on number of syllables (one to four) arequency (frequency ranged from 1 to 20ow, from 21 to 66 for medium, and from 70771 for high frequency items; means5 7.69,8.69, and 278.84 for the low, medium, aigh items, respectively, Francis & Kuce982). MS performed poorly, obtaining on6/174 (44%) correct (the picture “ambulanas removed as the name appeared withinicture). Performance varied as a function

requency, with high frequency items (77% cect; 24/31 correct) being named correctly more often than low frequency items (27% c

ect; 28/104 correct),x2 5 25.71, P , .005;however, there was no evidence for an effecnumber of syllables (see Table 1). Ninety-fipercent of MS’s errors consisted of circumlotions (i.e., descriptions of the meaning anduse of the item). For example, forcane:“This issomething you use to walk with if you hatrouble walking, if you have, you broke your lor something, and you need something to hyou walk.” This description clearly suggethat MS comprehends the concept “cane.”preponderance of semantic descriptions in Mresponses suggests that detailed semanticmation is available for objects that he canname.

It has been found that some anomic patiwho are initially unable to name a picturesuccessful when provided with a phonemic(Funnell & Hodges, 1991; Howard & Orchar

TABLE 1

Number Correct on the Philadelphia Naming Test asFunction of Frequency and Length

Frequency

Number of syllables

1 2 3 4

Low 14/48 10/37 4/16 0/3Medium 19/26 3/9 2/4 n/aHigh 19/26 5/5 n/a n/a

Lisle, 1984; Myers Pease & Goodglass, 1978).

st,tha(9n

rgemea

1/6o-

thentangl iicaeeedabn,S’s

iniev

aunepcti

ere_”nds).tebeth

ti-forunonon.

hextto

ing),ro-ondgubd

ria

urere-

ss aiched)iveand

-udi-inad-rdsrenl–redfer-t ofni-MSwaselaythis

anta-ains a

am-or-

toe-

ical(90eres,mes

naler-eniveactaff-n-


In a follow-up to the Philadelphia Naming TeMS was asked to name just those pictureshe had not been able to name on that testpictures). If unsuccessful, he was then givephonemic cue (the first phoneme of the taword). On this retest, MS was unable to na60 of the 98 pictures. When provided withphonemic cue, he was then able to name 3of those pictures. A beneficial effect of a phnemic cue on naming is consistent withhypothesis that output phonological represetions persist, but MS has difficulty activatithose representations. In terms of the modeFigs. 3 and 4, the connections between lexand phonological representations have bweakened but have not been totally disrupt

Access to syntactic features of nonnamepictures.In a recent study, Vigliocco, VinsoMartin, and Garrett (in press) examined Mability to make count/mass judgments whenan anomic state, that is, when unable to retrthe phonological form when trying to namepicture or produce a name to a definition. Covs. mass is a syntactic feature of a lexical rresentation that determines various syntaframes into which a word can be fit (e.g., “This a _______“ and “There won’t be many ___for count nouns vs. “There is _________” a“There won’t be much ________” for masAlthough the count vs. mass distinction relato conceptual features of the objects tonamed, there are some nouns for whichdistinction is quite arbitrary (consider “archoke” vs. “broccoli”). The objects chosenthis study were all selected such that the comass distinction was nonobvious from the cceptual features of the picture or definitiWhen MS was unable to provide a name,was asked to choose which syntactic contwere appropriate for the word he was tryingretrieve. He was highly accurate in makthese judgments (.80% correct on 91 trialseven on trials for which he was unable to pvide any segmental or syllabic informatiabout the word. His accuracy on these juments was within the range of 10 control sjects who were provided the names and askemake the same judgments about approp
syntactic contexts (mean accuracy5 85%).
t8at

0

-

nln.le

e

t-c

s

e

t/-

es

--tote

MS’s good access to this syntactic featwould suggest that even when he cannottrieve phonological information, he can accelexical representation (irrespective of whtheory of lexical representations is employand that his naming difficulty does not derfrom weak connections between semanticlexical representations.

Speech Perception

Auditory discrimination task.In order to assess MS’s speech perception abilities, an atory discrimination task (provided by N. Mart& Saffran, personal communication) wasministered. There were 80 pairs of nonwoand 80 pairs of words—half of which we“same” and half of which were “different.” Othe “different” trials the word (e.g., funnetunnel) and nonword pairs (beck–feck) diffein one phoneme and the position of the difence was varied. As a relatively pure tesauditory discrimination (that is, one that mimizes a short-term memory component),was asked to judge whether a pair of wordsthe same or different when there was no dbetween presentation of the two items. Incondition, MS obtained 99% correct. Whendelay of 5 s was introduced between presetion of the two members of the pair, MS agobtained 99% correct. Finally, when there wafilled 5-s delay (when the patient and the exiner counted out loud), MS obtained 98% crect. Thus, MS demonstrates a good abilityperform auditory discrimination in both no-dlay and delay (unfilled or filled) conditions.

MS was also tested on an auditory lexdecision task which included 180 wordsabstract and 90 concrete words that wmatched in frequency) (from Kroll & Merve1986) and 180 nonwords which differed frothe real words by either one or two phonem(provided by N. Martin and Saffran, persocommunication). MS scored 96% correct ovall with little difference in performance betwewords (172/180) and nonwords (173/180). Fof eight of the word errors were to abstrwords. In a second test (see N. Martin & Sran, 1992) of 160 items (80 words; 80 no
words) the words varied on imageability and

theaineceonrss.

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ch

Forted.

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frequency and the nonwords differed fromwords by one or two phonemes. MS agscored at a high level, obtaining 97% corroverall, with little difference in performancbetween the words (76/80 correct) and nwords (79/80 correct). All four word errowere to low frequency–low imageability word

Peabody picture vocabulary test.MS wastested on the Peabody Picture Vocabulary(Dunn & Dunn, 1981), which involves hearia spoken word and choosing from four pictalternatives the one that matches the word.performed in the low-normal range (standscore 5 86 relative to age-matched contrwhere m 5 100 ands 5 15). This level operformance clearly contrasts with histremely poor performance on a standardnaming test (i.e., the Boston Naming TeKaplan et al., 1983). However, the PPVT wnot specifically designed to include closemantic distractors among the nonmatchingtures. Thus, it might be possible to obtaingood score on this task despite having opartial semantic knowledge of many ofwords. Thus, several additional experimetasks were administered that tested semknowledge more closely. These were basetests developed by Hillis and Carama(1995), who demonstrated that these testsvealed semantic deficits in a so-called oaphasic patient where other more standardhad not.

Which is more closely related task.In thistask, the subject sees a picture of one objecis asked to pick the object that is most closrelated to it from a picture of a pair of obje(e.g., which is more closely related to adesk,atable, or a bureau?). In this task, both alterntives are related to the target object, but onmore closely related. This task was admitered to eight control subjects and only itemswhich there was a high degree of consiste(greater than 75%) in responding were incluin the test. MS obtained 19/22 (86%) correThis level of performance corresponds tomean for the control subjects (range5 13 to 22items correct).

Single spoken word-to-single-picture mat
ing. In this task, the subject sees a single pic
t

-

st

S

d;

--

licn

e-

ts

d

s-ryd.

-

tured object and is asked, “Is this a ____?”each word (e.g., “cat”), four trials are presenThe four trials included a correct picture (cat), apicture of a semantically related object (dog), apicture of an object with a phonologically siilar name (hat), or an unrelated (semanticallyphonologically) picture (nailclippers). The teswas administered over four sessions, with eword occurring once per session. This testnot administered to control subjects as it wassumed these subjects would obtain 100%rect. MS obtained 205/216 (95%) correct ovall, with all 11 errors occurring when worwere paired with semantically related pictu(e.g., “thread” paired with a picture ofyarn).MS’s 20% error rate (11/54) on the semanticrelated pictures might suggest that he has ssemantic disruption for these items. We decito further probe MS’s comprehension of th11 objects by presenting the pictured objectasking four questions designed to determwhether MS understood the differencestween the pictured object and the word thatbeen presented (e.g., for the pictureyarn whichhad been presented with “thread,” one ofquestions was: Do you knit with this?). Oquestion was asked at a time and the 11 pictwere cycled through four times in order to afour questions per picture. MS answered althe questions correctly, suggesting that hisrors on the word-to-picture matching task wnot due to comprehension failures, but mlikely to a low criterion for a match decisionwhen questions were focused so as to diguish between the members of each pair,performed perfectly.

Attribute questions for pictured objects.Inthis task, the subject is presented with a picof an object from one of the following categries: animals, vehicles, clothing, and ediplants. There were 33 animals, 26 vehiclesarticles of clothing, and 20 edible plants. Fquestions were asked about attributes ofpictured objects from each category. Forani-mals: Does it have fur? Does it eat other amals? Is it found in water? Is it domestic? Idangerous? Forvehicles:Does it require fuel? Iit primarily used for recreational purposes? I
-used on land? Is it primarily used to transport

c r?I ryF ye leD rina wab tioo ftec ryt wa cate veq keT Tht thaf 1s b-j gor deo

hep ons part an7 lly,o t

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1%0%d tohesion

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people? Is it quiet? Forclothing: Is it used inold weather? Is it for men? Is it formal weas it worn on the extremities? Is it an accessoor edible plants:Is it green? Is it primarilaten raw or cooked? Is it a fruit or a vegetabo you eat the skin? Can it be used in prepadessert? Presentation of the pictures

locked by category and, on each presentaf a picture, only one question was asked. Aompleting one question for a given categohe category was changed and one questionsked about all the pictured objects in thatgory. This procedure continued until all fiuestions for each category had been asesting occurred over several sessions.

ask was also administered to controls suchor each category, data were obtained fromubjects. Unlike MS, no individual control suect answered questions from all four cateies. Therefore, comparison to MS will be man a category-by-category basis.Before examining MS’s performance, t

erformance of controls was examined for cistency of responding. Items (questions foricular objects) for which there was less th5% agreement were eliminated. Additionane question for theclothing category (is i

worn on the extremities?) was removed becaMS seemed unfamiliar with the concept of “etremity.” After the removal of these items, Mobtained 134/139 (96%) correct on the qutions aboutanimals,109/111 (98%) correct foehicles,103/105 (98%) correct forclothing,

and 83/90 (92%) correct foredible plants.Forall the categories except foredible plants,MS’s

TAB

Performance of MS and Control Subjefor Pictured Objects—

Animals V

S 134/139ontrolsMean (SD) 131 (5.09)Range 120–136

performance was above the mean for the controa

?

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d.ist,6

-

--

e

-

subjects (see Table 2). However, MS’s permance foredible plantsfell just outside of thrange for the controls.2

In order to compare comprehension and ning performance for the same set of items,was asked to name the pictures that hadused in this comprehension test. MS nam45/104 (43%) of these items. There wasindication that MS’s naming deficit is due tosemantic impairment: MS failed to name 6(51/84) of the items for which he scored 10on the comprehension task, whereas he failename only 35% (7/20) of the items for whichmade an error on one of the comprehentests.

SUMMARY OF PERFORMANCE ONCOMPREHENSION TASKS

MS performed at, or above, the mean forcontrol subjects on several of the comprehsion tasks. The exceptions were the questprobing knowledge about picturededible plantsand the semantically related trials for the pture–word matching test (in fact, controls wnot tested on the picture–word matching tesit was assumed that their performance wouldat 100%). On the edible plants questions, Mperformance fell just outside the range of

2 There are several instances reported in the literatuerpes encephalitis cases who have a selective disruptemantic knowledge for living things (see Saffranchwartz, 1994), and it might be hypothesized that Meficit for plants reflects a mild version of this patteowever, these patients tend to show impairments fornimals and plants and there was no evidence that MS

2

on Questions Probing Semantic Knowledgeumber of Items Correct

Category

icles Clothing Plants

/111 103/105 83/90

(3.08) 100 (3.86) 88 (1.–109 93–105 85–9

LE

ctsN

eh

109

10598

ln impairment for animals.

tedS

nticon

l ofde

r-in

nticndte-y

c obs ton mp rl ens edp ntick icha rel

t ap , ac int con ntt ionr rmas bt iona fol rdf 90a thel ew bet ionh enc tios upt s

andc omr calr sent

ordutrd

ort-

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ichtest20

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controls. With regard to the semantically relapicture trials, further probing indicated that Mhas a good ability to distinguish the semaproperties of pictures and words for the trialswhich he had made errors. MS’s high leveperformance on tasks designed to requiretailed semantic knowledge (Hillis & Caamazza, 1995) argues strongly that his namdeficit is not the result of an impaired semasystem. Even though there may be some ication of a semantic deficit limited to the cagory edible plants,this potential deficit clearlannot account for the pattern of resultserved with MS. Additionally, when askedame the pictures involved in some of the corehension tasks, there appeared to be little

ationship between his naming and comprehion. For those items for which he performerfectly on the questions probing semanowledge, he named only 39% (33/84), whgain argues that his naming deficit is not

ated to a semantic impairment.These results, along with the finding tha

honemic cue benefits naming performanceonsistent with the hypothesis that MS hasact semantic representations and that theections between lexical–semantic represe

ions and output phonological representatemain, but have been weakened. For noubjects, we assume that the connectionsween lexical and phonological representatre stronger for high frequency words than

ow frequency words (for discussions of worequency effects in production see Dell, 19nd Jescheniak & Levelt, 1994). To explain

arge frequency effect in naming for MS, would hypothesize that the connections

ween lexical and phonological representatave been damaged for words of all frequies, but because of the weaker connectrengths for low frequency items, the disrion to naming is more evident for these item

SHORT-TERM MEMORY

MS’s performance on the naming tasksomprehension tasks suggests that his aneflects an inability to activate phonologiepresentations from lexical–semantic repre
ations and is not a result of degraded semant
-

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re-n-a-sl

e-sr

,

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ia

-

representations or damaged phonological wforms. If this same ability to activate outpphonology from semantics is involved in wolist recall, then MS should be impaired on shterm memory tasks as well.

Digit Span and Digit Matching Span

Our initial evaluation of MS included thforward digit span task from the WAIS-(Wechsler, 1981). On this test MS repeatedlists perfectly up to the eight-item lists, at whpoint he missed 1 of 2 lists. On a subsequentof digit span using a pointing response (withlists at each list length), MS scored at a norlevel, obtaining 100, 90, 85, and 80% correctfour-, five-, six-, and seven-item lists, resptively. He also performed well on a digit matcing span task. In this task, the subject healists containing the same digits and is askejudge whether the order of the items is the sor different across the 2 lists. On the nonmaing trials, the second list reverses the ordetwo adjacent items. Position of the reversalbalanced across serial positions. There werlists with 10 matching and 10 nonmatchingals. MS’s performance was excellent, as hetained 95% correct on six-item lists (the melevel of performance for six control subjewas 93% correct; range, 85–100% correct)

The digit span results suggested that MSnormal short-term memory and thus appearecontradict the hypothesis of a close relabetween word production processes and liscall. However, digits are high frequency wo(the word frequencies for the digits 0 to 9 ranfrom 81 to 3372 per million, with a mean729.33 and standard deviation of 1074.93; Fcis & Kucera, 1982) and, as indicated indiscussion of the naming results, MS’s namability was much worse with low frequenwords.

Word List Repetition

Words vs. nonwords.One piece of evidencthat semantic information supports recall comfrom the observation that memory spangreater for word lists than for nonword lis(Brener, 1940; Crowder, 1978; Hulme et
ic1991; Multhaup et al., 1996). MS was thus

sts

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tested on the recall of word and nonword liThe words were of low frequency (,10 permillion, Kucera & Francis, 1967) and the nowords were formed by switching phonemamong the words. A standard span procewas used in which list recall began withtwo-item lists and list length was increasedincrements of one until lists were five itemslength. Items were drawn from the same pfor each presentation. Spoken recall was u

The results are shown in Table 3. MS didshow the standard pattern of better recallword than for nonword lists—at no list lengdid MS show an advantage of word over nword recall. Recall was actually slightly worfor the word lists than the nonword lists, sugesting that MS’s recall does not benefit frthe semantic information provided by worSix control subjects were tested at list lengthree through five. As can be seen in TablMS’s recall of the nonword lists was within tnormal range, while his word recall was belthe range of controls for the four-item lisCollapsing across list length, all six control sjects showed an advantage of word recall ononword recall (mean advantage, 21%;11.43). For only one subject, at one list leng

TABLE 3

Percentage of Lists Correct for Word and Nonword LMatched in Constituent Phonemes—Repeated Samfrom Same Pool

List length

2 3 4 5

SWords 100 100 60 2Nonwords 100 100 80 2

List length

3 4 5

ontrol subjects—Mean level of performance (range)Words 98 90 52

(90–100) (80–100) (10–80Nonwords 90 63 25

(90) (30–90) (0–60)

did nonword recall exceed word recall: At list

.

e

l.

tr

-

s,

r,,

length four, one subject recalled one more nword list than word list.

We also had MS recall word and nonwolists that did not repeatedly sample fromsame pool (in order to make the task mcomparable to the recall tasks reported beloWord lists consisted of low frequency wor(,10 per million, Kucera & Francis, 1967while the nonwords again were formed byarranging the phonemes contained withinwords. As can be seen in Table 4, we agobtained evidence that MS’s recall doesbenefit from the semantic information providby words (indeed, for four-item lists substatially more nonword lists were recalled thword lists). A comparison with seven contsubjects indicates that MS performed at a hlevel in recalling nonwords. However, in recaing word lists, MS again scored below the raof control subjects on the four-item lists. Clapsing across list length, all seven control sjects showed an advantage of word recall ononword recall (mean advantage, 30%;7.14). For only one subject, at one list lengdid nonword recall exceed word recall: At llength five, one subject recalled one nonwlist and no word lists.

Words varied on frequency and imageabilMS was also tested on list repetition tasks pvided by N. Martin and Saffran (see SaffranMartin, 1990; Martin, Saffran, & Dell, 1996)order to examine effects of imageability a

TABLE 4

Percentage of Lists Correct for Word and Nonword LMatched in Constituent Phonemes—New Items onList

List length

3 4 5

MSWords 100 30 20Nonwords 100 70 10

Control subjects—Mean level of performance (Range)Words 99 84 17

(90–100) (70–100) (0–4Nonwords 80 27 1

(60–90) (10–40) 0–10

g

0

vi-ar-lsovi-typorre-tsnd

il-n aadi-

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rors( thed deo or-r ble6 d ap rd,i or-m it is

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frequency on list recall. As indicated preously, N. Martin and Saffran (1992, 1997; Mtin et al., 1996; Saffran & Martin, 1990; see aR. Martin & Lesch, 1996) have obtained edence suggesting an association betweenof STM impairment (phonological, semantic,mixed) and patterns of imageability and fquency effects on list recall. Half of the liswere composed of high imageability words ahalf of low imageability words. High imageabity words had ratings greater than 4.97 (oscale of 1–7), while low imageability words hratings less than 4.97 (Paivio, Yuille, & Madgan, 1968). Within each level of imageabilihalf of the lists were composed of high fquency words and half of low frequency worHigh frequency words had frequenciesgreater than 40 per million, while low frequenwords had frequencies of less than 30 perlion (Kucera & Francis, 1967). MS was psented with 80 three-word lists and 60 foword lists. Spoken recall was used. Overall,recalled 83% of three-word lists and 55%four-word lists. The percentage of lists corrby frequency and imageability is shown in Tble 5. MS showed substantially better recallthe high than low frequency lists for both llengths (for list length three, 39/40 lists27/40: x2 5 12.47, P , .005; for list lengthour, 23/30 vs. 10/30:x2 5 11.38,P , .005).An effect of imageability was evident within t

TABLE 5

Percentage of lists correct as a function of frequenc(HF, LF) and imageability (HI, LI)

MS Controls

3-word 4-word 4-word 5-wor

FHI 95 80 97 71LI 100 73 96 65Mean 98 77 97 68

FHI 70 60 95 53LI 65 7 89 41Mean 67 34 92 47verall mean 83 55 94 58

four-word low frequency lists where he showed

e

.

-

t

r

much better recall of the high than low imaability lists (9/15 vs. 1/15:x2 5 9.60,P , .005).n terms of items correct at each serial posithe pattern of recall was similar for both lengths (see Fig. 5)—a reduced recency end an effect of frequency particularly at la

ist positions. This pattern is consistent wata that N. Martin and Saffran (1997) habtained from patients with presumed pho

ogical deficits.Table 6 presents a breakdown of the er

collapsed over list length) that MS made forifferent list types. These errors do not inclurder errors (i.e., reporting an item in the incect serial position). As can be seen from Ta, a high percentage of MS’s errors sharehonological relationship with the target wo

ndicating that MS retained phonological infation about the words in the lists. Further,

FIG. 5. Frequency and imageability effects as a func
of serial position (Martin & Lesch, 1996).

tedmoe-

seherly-

he“itamin

e-ticof

tiore-ility

o0%ur

calnt

ofostntic

ll ofe-inencer-d totedts.thein

ub-ncytsre-

),reity

ar-

91

ogicallydr of errors


interesting to note that phonologically relanonword responses appeared somewhatlikely than phonologically related word rsponses. We will return to this point later.

MS’s responses also quite often includedmantic descriptions of the words within tlists. This type of response was particulalikely in the recall of low frequency, high imageability lists. For example, for the listlobster,castle,andbagpipe,he responded: “losser—tthing you eat, the place the kings go in,” andcomes from the place where men wear the sthings as women” (mimics use). As shownTable 6, 32% of MS’s errors on the low frquency, high imageability lists were semandescriptions of the items. An additional 37%his errors consisted of a semantic descripcombined with a phonologically relatedsponse. On the low frequency, low imageablists, 5% of MS’s error responses consistedsemantic descriptions, while an additional 1were semantically related words. The occrence of semantic descriptions in MS’s resuggests that MS at times retained sema

TAB

Percentage of Error Types in List Recall as a F

Sa SD P-W P-NW

Patient MSHF

HI 0 20 0 40LI 0 0 33 33

LFHI 0 32 11 11LI 10 5 22 37

ControlsHF

HI 0 0 29 0LI 0 0 18 0

LFHI ,1 0 21 ,1LI 0 0 17 1

aNote.S, semantically related word; SD, semantic derelated nonword; SD1 P, semantic description combinephonologically related response; U, unrelated; O, omisfor that list type.

information about a word that he could not

re

-

e

n

f

-lic

produce correctly. The greater likelihoodthese errors on high imageability items mlikely occurred because of the richer semainformation in these items.

Control subjects were tested on the recaboth four- and five-item lists varying on frquency and imageability in order to determwhether MS’s level and pattern of performawould differ from those for controls. The fouitem lists were those that MS had been askerecall, while the five-item lists were construcby rearranging words from the four-item lisFive subjects participated in the recall offour-item lists, while 36 subjects participatedthe recall of the five-item lists.

The recall performance of the control sjects demonstrated effects of both frequeand imageability: In the recall of five-item lissubjects recalled significantly more high fquency (68%) than low frequency lists (47%t(33) 5 8.96,P , .001, and significantly mohigh imageability (62%) than low imageabillists (53%),t(33) 5 3.83,P , .001. Finally, theFrequency X Imageability interaction was m

6

ction of Frequency (HF, LF) and Imageability (HI, LI)

Error types

(SD1 P) U O Other N

0 0 40 0 50 17 17 0 6

37 0 11 0 15 0 17 5 4

3 4 55 110 5 70 7

,1 0 70 8,1 2 77 3

ption; P-W, phonologically related word; P-NW, phonolith a phonologically related response; S1 P, semantically ann; Other, some other type of response. N, total numbe

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results thus replicate previous studies demstrating frequency and imageability effectslist recall (e.g., Hulme et al., 1991; BourassaBesner, 1994) and further provide somedence that these factors interact in supporretention (this pattern of results is similar to tobtained by Lesch & Martin, 1998).

As is evident in Table 5, MS performed sustantially worse than the controls. Control sjects recalled 94% of the four-item lists (ran5 87–100%) compared to 55% of lists corrfor MS. The mean performance of the contron the five-item lists (mean, 58%; range, 7–9correct) was similar to MS’s level of recall fthe four-item lists (55% correct). Although boMS and the control subjects showed effectfrequency and imageability, there was somedication of greater effects of these variablesMS than the controls. These comparisonssomewhat difficult to make, given the differelevel of performance for MS and the controHowever, some comparisons can be madeevaluating the effects of frequency and imaability when MS and the controls are matchfor performance on certain cells (necessarildifferent list lengths). For example, MS’s levof performance on the high frequency thrword lists (98%) was similar to that of controon the four-word high frequency lists (97%However, MS showed a much greater frequeeffect on the three-word lists (31%) than didcontrols on the four-word lists (3%). Also, tlevel of performance for MS on the high frquency four-word lists (77%) was fairly similto that of the controls on the high frequenfive-word lists (68% correct), but again Mshowed a much larger frequency effect onfour-word lists (43%) than did the controlsthe five-word lists (21%). It should be notethough, that on the four-word lists, the larfrequency effect for MS was due primarilyhis very poor performance on the low fquency, low imageability lists. For the low frquency four-item lists, MS showed a mularger effect of imageability (53%) than did tcontrols for the low frequency five-word lis(12%) even though MS and the controls wapproximately matched in their level of rec
for the low frequency, high imageability items.
-

-gt

-,t

f-re

y-

t

-

y

e

In order to explore the types of errors maby control subjects, mean error rates wereculated as a function of frequency, imageabiand error type. Subjects who accurately recaall the lists in any frequency–imageability codition were excluded. The mean error ratespresented in Table 6. The error distributioappear quite different for MS and for the consubjects. Whereas MS provided a large percage of semantic descriptions, control subjnever provided semantic descriptions ofitems to be recalled and only very rarely pduced semantically–related responses. Ationally, control subjects very rarely made pnologically related nonword responses, wthis type of response was quite commonMS’s recall. The predominant error typesthe controls were omissions and the substituof phonologically related words. Thus, not odoes MS’s level and pattern of performadiffer from that of control subjects, the typeserrors also differ (even when overall levelrecall is approximately matched).

List recall—Names of pictures named/named and words with and without comprehsion errors.MS performed at a high level onvariety of tasks that require the access oftailed semantic information, suggesting thatpoor performance on list recall is not the reof insufficient semantic support due to disrupsemantic representations. In order to provfurther evidence on this point, MS was testedrecall of lists of words corresponding to tnames of pictures that he could or couldname and words for which he made or didmake comprehension errors. Given MS’s gerally high level of performance on the sematasks, it is difficult to claim that his semanknowledge for items with errors was actuadisrupted relative to controls, since his leveperformance was similar to that of controlsmost tests. That is, even though MS madeerror on, for example, one attribute of an obin the attribute questions task, his performacould not be said to differ from controls sinthey also made such errors at a similar rathough perhaps not on the same items. Hever, if one takes a conservative approach
hypothesizes that MS does in fact have some

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degree of semantic deficit for the itemswhich he made errors, then recall shouldworse for lists of items for which MS demostrated some comprehension difficulty (Warrington, 1975; McCarthy & Warringto1987; Patterson et al., 1994).3 On the othehand, if difficulty in phonological retrieval underlies his naming deficit, and if list recall ivolves the same phonological retrieval pcesses involved in naming, then list recshould be worse for items he could not nathan for items he could name.

Items that MS could/could not name wtaken from the Philadelphia Naming Test. Itethat MS could/could not comprehend wtaken primarily from the comprehension tareported above. Items for which there wasstrongest evidence of comprehension diffic(items that were responded to incorrectlymore than one task) were selected first. MSpresented with 10 four-item lists of the folloing types: (a) items that MS could name,items that MS could not name, (c) itemswhich MS made errors on the comprehenstests, and (d) items for which MS madeerrors on these tests. The named/not namedwere approximately matched in terms of fquency and number of syllables. The comphended/not comprehended lists were amatched in terms of number of syllables, buthere were relatively few items for which Mdemonstrated comprehension difficulty, it wdifficult to match lists in terms of frequency. Alists were presented auditorily and spoken rewas used. This task was administered tw

3 Warrington (1975; McCarthy & Warrington, 1987) fimployed the known/unknown technique to study patith characteristics similar to the patients of Patterson

1994) and failed to observe a significant advantagenown compared to unknown items. Patterson et al. pohe different methods used to select known/unknown is one possible source of the discrepant findings.

urther suggest that the near ceiling levels of performy Warrington’s (1975) patient on the unknown items sests that, at the time of initial testing, the patientaintained semantic knowledge for these items. At thef a second testing, when a comparison of unknown w

o nonwords was made, performance had dropped corably for these items. However, no comparison was m

eor the known items.

e

l

e

s

n

ts

-os

ll,

with the second testing occurring approxima6 months after the first testing.

As the pattern of performance was simacross the two administrations, we will repmeans collapsed over administration. MSbetter able to recall lists composed of itemshe could name (95% lists correct; 99% itecorrect) than lists of items that he couldname (55% lists correct; 81% items correct),lists correct (19/20 vs. 11/20),x2 5 8.53,P ,.005, for items correct (79/80 vs. 65/80),x2 513.61, P , .005. In contrast, there was

ifference in the recall of lists composedtems for which he showed perfect comprehion (13/20 lists correct; 72/80 items correersus those for which he made any comension errors (13/20 lists correct; 71/80 iteorrect). MS’s pattern of performance on tecall task strongly argues that a semanticcit is not the basis of his poor performanceist recall—MS’s level of recall appears tonrelated to his accuracy in responding toomprehension questions for particular itehis contrasts with the observation that Mecall was poorer for lists composed of iteorresponding to pictures that he was unabame in a naming task than for items that heeen able to name, again indicating a strorrespondence between his ability to retrihonological representations in word prod

ion and list recall.

DISCUSSION

To summarize, MS showed normal list recor digits and nonwords, but impaired recallords. Word recall was particularly impair

or low frequency words and within low fruency words, for low imageability wordS’s normal recall of nonword lists indicat

hat he does not have difficulty in maintainnd reproducing phonological informatione. However, MS does not show the boosecall from the lexical–semantic informativailable in words that is shown by normubjects. Consistent with the suggestion oeduced lexical influence on recall is the prlence of phonologically related nonwordponses in MS’s recall. The phonological re

sl.rosye-

esd-e
dness of the responses suggests an ability to

alhoof

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retain phonological information. For normsubjects, feedback from the lexical to the pnological level should prevent the productionnonword responses, and few were observeour control data. The few that were obseroccurred for low frequency lists, suggesting tsome of the subjects may not have been famwith some of the items. (Note that MS manonword responses to both low and highquency items—see Table 6.) MS’s recallword lists suggests that recall is characterby the same difficulty in retrieving phonologicrepresentations from semantics that is chateristic of his naming. A large effect of frquency was evident in both his naming andrecall presumably due to the weaker conntions between semantics and phonology forfrequency words. MS’s very good performanon digit span lists compared to word lists canattributed to the high word frequency of dig

Further evidence of the concordance betwMS’s word production and list recall was edent in the errors that MS made in list recThat is, MS at times produced circumlocutioin list recall that were similar to his circumlcutions in naming. In these cases, MS recathe meanings of the items contained withinlist rather than the items themselves indicathat the words had been accurately perce(indicating intact input phonological represtations) and that appropriate semantic repretations had been activated. These semanticscriptions were most likely to occur in tcondition where retrieval of phonological formwould be assumed to be most difficult (lfrequency words), but where semantic informtion should be most readily available (high iageability words), indicating that, while semtic information had been activated, it couldbe used to retrieve the appropriate phonologform. A comparison of MS’s error types withose of controls indicated that control subjenever provided semantic descriptions ofitems to be recalled. Other evidence of a cospondence between word production andrecall came from MS’s recall of lists corrsponding to the names of pictures whichcould or could not name. Better performa
was obtained for words he produced as name
-

in

tr

-

d

c-

t-

n

d

d

n-e-

-

l

s

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than for those he could not produce as namThis result contrasted with equivalent perfmance on lists composed of words for whichdid or did not make errors on the comprehsion tests.

MS’s naming and list recall responsesverged in that he produced many more phological approximations (both word and noword forms) in list recall than he had in naminThis difference can be attributed to the factphonological information is presented to MSthe list recall tasks, and, as indicated byrecall of nonwords, he has a good ability to honto phonological information. Thus, he cuse this surviving phonological informationconstrain his responses. In naming, phonolcal information is not provided, but has toretrieved.

The results of the word vs. nonword rectasks and the task manipulating frequencyimageability of words might appear contradtory. Specifically, the failure to find an advatage for words over nonwords would seemcontradict the finding of an imageability effefor MS.4 Our discussion of the word vs. noword results focused on the low frequencythe words and MS’s poor ability to retrieve lofrequency words. However, since words wobe bound to be more imageable than nonw(and the words we used in these tasks wfairly imageable), an advantage for words mibe predicted. One possible explanation forfailure to find an advantage for words (andfact, the finding of a slight numerical disadvatage for words) is that with words, a semanrepresentation is activated which leads toactivation of incorrect but semantically relawords on the output side. If these related woare of higher frequency than the target wothe phonological forms of the related womay become highly activated and interfere wthe retrieval of the phonology of the targwords. With nonwords, there would be no copetition from words activated from semantiAccording to this logic one would see boimageability and frequency effects for worbut the performance for nonwords would

4
s We thank an anonymous reviewer for this suggestion.

o

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necessarily be worse than that for any typeword.

Up to this point, we have provided evidenthat MS demonstrates difficulties in recall tathat require verbal output (i.e., output phological representations). Within a model tdistinguishes between input and output phoogy, the data suggest that MS has difficultythe output side in retrieving phonological formIf one further assumes that there are sepainput and output phonological buffers, Mmight be predicted to perform well on tasks trequire only the retention of input phonologiforms.

STM for Input Phonology

For the most part, these tasks did not reqoutput of words from the memory lists, brather a yes/no judgment about whether a pword or list matched the preceding list. Previevidence indicated that MS has a good abilitretain semantic information from word liseven when he cannot retrieve appropriate pnological forms corresponding to these semtic representations. Thus, it was necessarensure that these tasks tapped the retentiophonological information rather than semainformation. The first task, a rhyme probe tarequired phonological information in ordermake the rhyme/nonrhyme judgment. The ntask required the retention of order informatiwhich has been argued to rely on the retenof phonological information (e.g., Wickelgre1965).

Rhyme probe task.In the rhyme probe tasthe subject judges whether a probed wrhymes with any item in a preceding list. Livaried from 1 to 7 items in length and numbelists at each list length varied from 20 to 28. Feach list length, half of the trials were rhympresent and half rhyme-absent. On rhympresent trials, each serial position was proequally often. MS’s performance was similarthat of control subjects who were roughmatched with MS in terms of age and educalevel. MS’s estimated span (75% correct permance) was 6.4 items, while the mean forcontrol subjects was 7.08 (SD, 1.44) items.

As MS’s performance on the repetition tasks

f

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e

--oof

,

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-

was more impaired for low frequency thanhigh frequency words, we constructed a nrhyme probe task that used only low freque(,30 words per million; Kucera & Franci1967) and low imageability words (,497 on ascale of 100 to 700; Oxford PsycholinguisDatabase, Quinlan, 1992). While a frequevalue of 30 may not seem a particularly lcutoff for low frequency words, this is the sacutoff that was used in the lists for recall tvaried on frequency and imageability andwhich MS showed a large effect of frequenList length varied from four to six items anumber of lists at each list length varied fromto 24. As can be seen in Table 7, MS performat a high level relative to six control subjectsorder to assess whether this level of permance would be stable across test sessionswas tested a second time on this task. Hetained 100, 85, and 83% correct for list lengof four, five, and six, respectively—a levelperformance which again compared favorato that of control subjects (see Table 7).

Order recognition task.In the order recogntion task the subject hears an eight-item liswords followed by a pair of adjacent worfrom the list (with all serial positions beinprobed equally often). The pair of words eitare in the same order as they occurred withinlist or they are in the reverse order. The subis asked to decide whether the word orwithin the pair is the same as it had been withe preceding list. Items were one, two, or thor more syllables in length and presentation

TABLE 7

Percentage of Correct as a Function of List Lenghyme Probe Task (Low Frequency–Low Imageabords)

List length

4 5 6

MS 94 95 100Controls

Mean 89 86 70Range (81–94) (80–95) (58–8

blocked by item length. There were 48 lists at

am8

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96)


each list length and an equal number of sand different trials. As can be seen in TableMS performed at least as well as control sjects on this task.

We also constructed an order recognitionusing only low frequency (,30 words per milion, Kucera & Francis, 1967) and low imagbility words (,497 on a scale from 100 to 70xford Psycholinguistic Database, Quinl992). In this version of the task, subjects he8 lists of eight two-syllable words. MS pe

ormed at a high level, obtaining 89% (25/2orrect. Again, MS’s performance comparedorably to that of six control subjects (me0%; range, 54–79% correct). Indeed, he

ormed at a higher level than the control sects. In a second administration, MS’s leveerformance was equivalent to his performan the initial testing (89% correct), indicati

hat he reliably performs well on this ordecognition task.

Nonword probe task.In the nonword probask the subject hears a list of nonwordsowed by a nonword probe. The subject mecide whether the probe item occurred inreceding list. List length varied from threeve items and each serial position was proqually often. Half of the probes occurred inreceding list, while half did not. Of thorobes that did not occur in the precedingalf were phonologically similar (they sharn onset with one item and a body with ano

tem—e.g., the probe “lirb” given the list itemjirb” and “lez”) and half were phonologicallissimilar. Number of lists at each list lengaried from 20 to 24. The results for MS and

TABLE 8

Percentage Correct as a Function of ItemLength—Order Recognition Task

Number of syllables

1 2 3

MS 79 81 73Controls 77 76 76

ix control subjects are presented in Table 9. A

e,-

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e

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d

,

r

an be seen in Table 9, MS performed at a hevel on this difficult nonword probe task.

DISCUSSION OF PERFORMANCE ONSTM TASKS TAPPING INPUT

PHONOLOGY

MS demonstrates an impairment in STasks that require word production—MSalled only 83% of the three word lists and 5f the four word lists that were varied on fuency and imageability. Interestingly, MS

imes reported the meanings of the words inist rather than the words themselves, indicahat the words had been accurately percend the appropriate semantic representation

ivated. We suggested that MS’s deficit refledifficulty in retrieving output phonologic

epresentations from semantics. Consistenthis interpretation, MS’s pattern of performans quite different on STM tasks that do nequire verbal output. On all the tasks repoere, MS’s performance was comparable tof control subjects. Our results are thus con

ent with an interpretation in terms of a sepaion between input and output phonology aneparation between input and output phonocal buffers.

However, there is some indication thatay actually be underestimating the extenS’s impairment in the retention of output phological codes since the control subjectsot tend to perform as well as MS on the in

asks. The differing patterns of performanceibited by MS on input and output tasksnderscored by a comparison of MS withdditional control subject whom we tested

TABLE 9

Percentage Correct as a Function of ListLength—Nonword Probe Task

List length

3 4 5 6

MS 96 96 75 88Controls

Mean 95 90 93 86Range (79–100) (79–100) (80–100) (75–
s

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both the order recognition task (with low frquency–low imageability words) as well asrecall of word lists varying on frequency aimageability: On list recall, MS only recalle55% of four-word lists compared to 100% crect recall for the control subject. However, tcontrol subject only obtained 75% correctthe order recognition task, while MS obtain89% correct (no individual subject performedwell as MS on this task). Even though nonethe controls performed as well as MS did onorder recognition task, there appeared tolittle difficulty in performing a task requirinoutput phonological codes—a task for whMS only obtained 55% lists correct.

We have suggested that the dissociationstween performance on input and output phological STM tasks can be interpreted as supfor the notion that there are separate inputoutput phonological representations and srate buffers for retaining these representatiAs discussed in the introduction, it is necessto consider whether a model such as thshown in Fig. 3 with a single phonologicrepresentation could accommodate the findiIn such a model, MS’s disruption would bethe connections from semantics on the ouside. However, this approach runs into difficuin accounting for MS’s STM data. That is,there is one phonological buffer associated wstoring phonological forms derived from eithinput or output, it would be difficult to accoufor MS’s normal performance on input STtasks and poor performance on output Stasks. That is, if one assumed that a disrupin the connections from semantics to phonolwas the source of MS’s poor performanceoutput STM tasks, poor performance on inSTM tasks would be expected as well becaof the absence of feedback from the semantthe phonological level. This reasoning assuthat input tasks are affected by lexical–semafactors. One source of evidence in this regcomes from a recent event-related poten(ERP) study (Ruchkin, Berndt, Johnson, Gman, Ritter, & Canoune, 1998) that examinperformance for words versus nonwords orecognition probe task, which would be a t
tapping input retention. These researchers foun
f

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a

differences in the topographical pattern of ERfor words versus nonwords that were evidboth during encoding and during a 6-s reteninterval.

SUMMARY AND CONCLUSIONS

We have reported data from an anomictient, MS, whose naming performance cancharacterized as demonstrating greater dculty in producing lower frequency words aretention of detailed semantic information abobjects that cannot be named. Rigorous tesprovided evidence of preserved semanticlexical information about names that couldbe produced and we concluded that MS’s ning deficit derived from weakened connectibetween lexical and phonological represetions.

According to models such as those showFigs. 3 and 4 that postulate a close connecbetween word processing and short-term mory, the weakened connections between lexand phonological representations should hpredictable consequences for STM permance. That is, MS should not show the bento recall that derives from the flow of activatifrom semantic and lexical representationsphonological representations on the output sand the factors that influenced his abilityretrieve phonology in single word tasks shoinfluence his STM performance. We found tto be the case: (a) MS’s performance didshow the advantage normally seen in wordcall relative to nonword recall; (b) word frquency exerted a strong influence on his Sperformance, with higher frequency items bemore likely to be recalled than lower frequenitems; (c) specific items that were unlikely tonamed were less likely to be recalled in a shterm memory task than were items that had bcorrectly named; and (d) MS produced circulocutions in list recall as he did in naming tas

The data from MS also provided evidenrelevant to distinguishing between a model sas those in Fig. 3, with a single phonologirepresentation underlying both input and outand that in Fig. 4, with separate input and ouphonological representations and input and
dput phonological buffers. In support of the sep-

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arate buffers interpretation we observed twhile MS’s performance on short-term memtasks suffered when verbal output was requihis performance was normal on short-tememory tasks that did not require verbal outA model such as that in Fig. 3 would hadifficulty accounting for these findings, unleswere assumed that somehow performanceinput STM tasks were uninfluenced by feedbfrom the lexical and semantic levels.

The current investigation thus provides fther support for the notion that verbal STinvolves the maintenance of the various levof representation involved in word perceptand production. These results are consiswith the claim that the short-term retentionverbal material depends on the activationlong-term memory representations (phonolcal, lexical, and semantic) for words andmaintenance of this activation in short-tememory. While our approach suggestsLTM makes its contribution during encodiand retention, an alternative view is that LTrepresentations exert an influence at the poirecall.5 For example, Hulme et al. (1991) hpothesize that at recall lexical representatare automatically retrieved and are used toinstate information in decayed memory tracesince nonwords lack these representations,tern completion should be more successfulwords than for nonwords. A similar account

5 It should be noted that these relatively recent attempttribute various aspects of span performance to aontribution differ from earlier accounts of span perance as deriving from recall from both short- and lo

erm stores (e.g., Waugh & Norman, 1965; Craik, 1971hese recent accounts, what is meant by LTM is the usemantic” memory to aid recall—that is, long-term knodge of lexical and semantic representations of words. Iarlier accounts what was meant by LTM was “episoemory. According to these earlier views, informa

bout a specific list (i.e., what words were presented inrder at a particular point in time) was represented inTM and LTM. At the time of recall, items could

ecalled from either STM or LTM. Neuropsychologividence argues against this earlier view in that amnatients with very impaired ability to learn new informati.e., impaired episodic memory) but preserved knowlef words (i.e., preserved semantic memory) show noemory span performance (Baddeley & Warrington, 1
evin, Benton, & Grossman, 1982).
t,

,

.

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s

nt

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t

f

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t-r

the lexicality effect has been offered by Schickert and colleagues (Schweickert, 19Schweickert, Ansel, & McDaniel, 1991), wterm the reconstruction process “redintegtion.” Roodenrys et al. (1994) have suggesthat redintegration can also account for thequency effect—phonological representationlong-term memory are more accessible for hfrequency words than for low frequency worThus, according to a redintegration accoeffects of lexicality and frequency are due torelative retrievability of lexical phonologicrepresentations at the time of recall. Howean effect of imageability (e.g., BourassaBesner, 1994) is not easily attributed to redtegration as there is no obvious reason topect that it would be easier to reconstruct hthan low imageability words from a degradphonological trace. That is, lexical phonologiinformation would seem to be as readily avable for low as for high imageability wordThus, while a redintegration approach encoters difficulty in accounting for semantic effeon STM, the language-based approach accofor both phonological and semantic effectsSTM by positing a close relation betweencodes stored in LTM (phonological, lexical, asemantic) and those active in STM—the pnological, lexical, and semantic representatshown in the left side of Fig. 3are the long-term

emory representations for the phonolognits in the language and for the semantic s

fications of known lexical items. The currendings form part of a growing body of dahat indicate that a disruption of these repreations or access to these language represions will have predictable effects on SToreover, the findings point to a need for srate representations for input and output pology in both language processing and sh

erm memory.

REFERENCES

Allport, D. A. (1984). Auditory verbal short-term memoand conduction aphasia. In H. Bouma & D. G. Bwhuis (Eds.),Attention and performance X: Contrand language processes(pp. 351–364). Hillsdale, NErlbaum.

Baddeley, A. D. (1986).Working memory.New York: Ox-

o

f

e

th

ic

el;

ford Univ. Press.

5).ory

ndory

an,atia

s: AA.

ge,

B toryl of

em-

th

l of

y

tic-

l

rmor,

val

typei-

ica

&and

ry.

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Received August 18, 1997)Revision received November 16, 1998)

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