The Language System in Schizophrenia: Effects of Capacity and

The Language System in Schizophrenia: Effectsof Capacity and Linguistic Structure

by Ruth Condray, Stuart R. Steinhauer, Daniel P . van Kammen,and Annette Kasparek

Abstract

Dysfunction in receptive language processes has beenreliably observed in individuals diagnosed with schizo-phrenia and their first degree family members. The pres-ent study addressed the unresolved issue of whetherreceptive syntax is intact in schizophrenia. The principalquestion concerned whether comprehension dysfunctionin schizophrenia involves a disturbance in the processingof syntactic structure, a susceptibility to demands placedon temporal auditory processing, or some combinationof these two general factors. Comprehension accuracywas compared between 32 males diagnosed with schizo-phrenia and 22 males with no lifetime diagnosis of psy-chiatric disorder. Accuracy was examined for responsesto Who questions ("Who did X?" and "Who was doneX?") about information in the sentential clauses (mainvs. relative) of two types of relative sentences (subject-relatives vs. object-relatives) that were presented aurallyat conversational and accelerated rates. The relationshipbetween cognitive functions and comprehension accu-racy was also tested. Results showed highly significanteffects of diagnosis, syntactic structure, and temporaldemand. Patients were characterized by reduced overallcomprehension accuracy compared to controls. Moreimportant, patients and controls differed in their pat-terns of accuracy across the different types of syntacticstructure. Finally, cognitive functions predicted but didnot completely account for comprehension accuracy.Findings suggest the hypothesis that receptive syntax isdisrupted in schizophrenia, and this dysfunction maynot be entirely explained by compromised general cogni-tive ability.

Keywords: Schizophrenia, receptive syntax, rela-tivization, word order.

Schizophrenia Bulletin, 28(3):475-490, 2002.

The language system has been assigned a central role inthe etiology (Crow 1997) and clinical manifestation

(Bleuler 1911; Kraepelin 1919; American PsychiatricAssociation 2000) of schizophrenia. Dysfunction in bothreceptive language and speech production has beendescribed for schizophrenia patients and their biologicalrelatives. Although speech production abnormalities aremore obvious as clinical signs and have been more com-monly targeted for empirical study (for recent reviews, seeDocherty et al. 1999; Docherty et al. 2000), dysfunction inreceptive language has also been consistently observed forpatients and their first degree family members, includingdisturbances in the perception of words presented aurallyat various levels of intensity (Bull and Venables 1974) andbackground noise (DeLisi et al. 1997; Shedlack et al.1997); and reduced comprehension accuracy for informa-tion in sentences (Thomas and Huff 1971; Faber andReichstein 1981; Morice and McNicol 1985; Condray etal. 1992, 1995, 1996; Landre et al. 1992; Goldberg et al.1998). The collective findings to date are therefore consis-tent with the hypothesis that integrity of the language sys-tem may reflect biological risk for the disorder. However,detailed analyses of complex behavioral phenotypes arerequired to provide a solid empirical basis for selectingvariables for genetic studies of schizophrenia (for discus-sion about the importance of this issue for behavior genet-ics in general, see Pennington and Smith 1997). If recep-tive language disturbance is to serve as an informativephenotype in behavior genetics studies of schizophrenia,detailed analyses of its underlying functional componentsare essential.

An important unresolved question is whether recep-tive syntax is intact in schizophrenia. Attempts to addressthis issue have involved a variety of strategies, includingcomparisons of schizophrenia patients and control groupson aphasia and neuropsychology test batteries, examina-tions of patients' sensitivity to syntactic structure, and

Send reprint requests to Dr. R. Condray, Western Psychiatric Instituteand Clinic, Department of Psychiatry, University of Pittsburgh School ofMedicine, 3811 O'Hara Street, Pittsburgh, PA 15213; e-mail: [email protected].

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evaluations of their accuracy in responding to complexsyntactic constructions. The findings from these empiricalefforts are not conclusive, although clear trends are pres-ent. Schizophrenia patients appear sensitive to syntacticboundaries in sentences (embedded click paradigm devel-oped by Fodor and Bever 1965: Rochester et al. 1973;Carpenter 1976; Grove and Andreasen 1985). In contrast,reduced accuracy has been documented for patients acrossa range of tasks involving complex syntactic construc-tions: carrying out instructions described in syntacticallycomplex sentences (revised Token Test: Morice andMcNicol 1985), ordering direct and indirect objects withinsentences (Rausch et al. 1980), and understanding logicalrelationships specified in relative-clause sentences (Con-dray et al. 1992, 1996). One linguistic feature common tothese latter studies is a transformational operation, move-ment of phrase constituents (Chomsky 1986; for a discus-sion regarding the relevance of movement to receptivesyntax in Broca's aphasia, see Grodzinsky 2000). Theappearance in schizophrenia patients of intact sensitivityto syntactic boundaries but disrupted syntactic movementrequires empirical refinement.

An additional unresolved question concerns the roleof extralinguistic capacities in schizophrenia patients' syn-tactic processing (for discussions relevant to language dis-orders in schizophrenia in general, see Schwartz 1982;Morice 1986; Frith and Allen 1988; Maher 1991). In par-ticular, results from several lines of investigation are sug-gestive about the importance of memory capacity inpatients' receptive language function. Knight and Sims-Knight (1979) reported an association between severity ofschizophrenia illness and the ability to organize and inte-grate in memory the ideas described in serial sentences.Grove and Andreasen (1985) observed that the perform-ance of patients and controls differed significantly for ashort-term memory task, but that those same individualsdid not differ for sensitivity to syntax boundaries in sen-tences or memory for gist in serial sentences. The resultsof Grove and Andreasen are consistent with the patternsreported earlier by Carpenter (1976) and Rochester et al.(1973). Moreover, memory span for sentence-length mate-rials has been found to correlate with overall comprehen-sion accuracy in patients and controls (Condray et al.1996). It has not been established whether patients' mem-ory capacity is associated with their processing of linguis-tic structures requiring transformational operations.

Theoretical Framework for the PresentStudyThe present study was designed to address the issue ofwhether receptive syntax is intact in schizophrenia. The

methodology involved examination of the influence ofsyntactic structure and psychological function on compre-hension accuracy in individuals with schizophrenia andnormal controls. The research was guided by a generalcapacity hypothesis that is broadly consistent with thecapacity theory of Just and Carpenter and their colleagues(Just and Carpenter 1992; Miyake et al. 1994; Haarmannet al. 1997) as well as earlier formulations in which theinteraction of syntactic parsing and semantic integrationwas emphasized (Perfetti and Lesgold 1977; Bock 1982;Kintsch 1988). The primary assumption was that dysfunc-tion of receptive syntax in schizophrenia is due, in part, tocapacity or activation disturbances that compromise thestorage and computation functions required to create rep-resentations of logical relationships that are specified bythe syntax of linguistic constructions. In the following dis-cussion, a limited review is provided for the two classes ofvariables of interest.

Linguistic Structure. The structure of language influ-ences understanding. Comprehension processes in non-clinical populations are affected by syntactic complexity,with systematic declines in comprehension accuracyaccompanying increases in complexity (for reviews, seeJust and Carpenter 1992; MacDonald et al. 1992). Insightinto receptive syntax in schizophrenia can therefore begained through examinations of the effects of syntacticstructure on understanding accuracy in this patient popu-lation, an approach that has led to increased understand-ing about receptive syntax in Broca's aphasia (for reviewand commentary, see Grodzinsky 2000). Structural factorsbelieved to influence comprehension include word order,transitivity, and relativization.

Word order. Word order specifies the logical rela-tionships that hold for a linguistic expression. Althoughdetermining the dominant or basic typology for a givenlanguage is not a straightforward issue (see Comrie 1981),English is typically considered a fixed-order language(Quirk et al. 1985), with the SVO (subject verb object)order representing the most consistent scheme (Siewierska1999). Most of the worlds' languages (95%) employ anSO ordering (subjects preceding objects) (for a review, seeSiewierska 1999), and it has been suggested that process-ing demand may influence the principle(s) that govern thisordering in some nonrandom manner (Bock 1982). Oneimplication of this assumption is that an OS ordering(objects preceding subjects) increases the demand on pro-cessing resources.

Transitivity. Transitive clauses communicate ideasabout "who did what to whom." Traditional definitions oftransitivity include the presence of a direct object and averb denoting that an action has been transferred from asubject to an object. More recently, the interface of seman-

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Effects of Capacity and Linguistic Structure Schizophrenia Bulletin, Vol. 28, No. 3, 2002

tic and syntactic knowledge has been emphasized, with adistinction made between semantic and syntactic aspectsand an emphasis placed on transitivity as a matter ofdegree (for a discussion, see Hopper and Thompson 1980).According to this perspective, the semantic aspects oftransitive clauses include the following: two participants,at a minimum, who fulfill the semantic roles of subject andobject; a subject who carries out a completed action in avolitional and controlling manner; and an object who ischanged by that action. The degree to which the completedaction creates a change in the object produces the contin-uum of transitivity.

Relativization. Most languages include relativeclauses (Fabb 1999; for an exception, see Comrie 1981),and these constructions have been used in theoretical con-siderations of transformational operations (e.g., move-ment: Chomsky 1986). Relative clauses commonly mod-ify nouns and are typically introduced with wh- pronouns(e.g., who, whom, which) and that (for discussions regard-ing the status of that as a relative pronoun, see Sag 1997;Van Der Auwera 1985; and for etymology, see Fabb 1999).In one method of relative clause formation, the noun-headto be modified can differ with respect to grammatical func-tion (subject vs. object) and location (before, after, orwithin the clause) (Keenan and Comrie 1977). Relativeclauses that are formed in this manner involve a modifica-tion of either the clause subject (subject-relative: Thedetective that shot the murderer . . .) or clause object(object-relative: The burglar that the fireman rescued...).

Psychological Functions. An assumption common to thevarious theories of language comprehension is that mean-ing is formed through multiple layers of linguistic struc-tures that are mutually constraining. According to thisgeneral framework, comprehension accuracy depends onsome combination of the processing efficacy that occursat the micro and macro levels: minimally, in the decodingof perceptual input (prerecognition lexical access models:McClelland and Elman 1986; Marslen-Wilson 1987;Marslen-Wilson et al. 1996; Wallace et al. 1998) and inthe integration of lexical items to create a grammaticalrepresentation (postrecognition computational models:Kintsch 1988; Just and Carpenter 1992; Haarmann et al.1997). In the comprehension of speech, this process mustalso be accomplished for lexical items that occur in a tem-poral sequence (Marslen-Wilson and Tyler 1980;Marslen-Wilson et al. 1996).

Two psychological functions have consistentlyemerged as important to comprehension processes in non-clinical populations: temporal auditory processing andmemory capacity.

Temporal auditory processing. There does appearto be an upper limit on the amount of linguistic informa-

tion that human beings can comprehend accurately perunit of time. Comprehension accuracy declines systemati-cally as presentation rates increase above the conversa-tional rate of 250 to 300 words per minute (Fairbanks et al.1957; Carver 1982; for a review of the early literature, seeFoulke and Sticht 1969; Wingfield 1975; Hausfeld 1981).Training with accelerated speech does not appear to elimi-nate these comprehension decrements entirely (Wallace1983). Deficits in temporal auditory processing may beintegral to certain developmental learning disorders, suchas dyslexia (for discussions, see Llinas 1993; Tallal et al.1993). Moreover, schizophrenia is associated with distur-bances in the processing of sequential, rapidly presentedauditory stimuli (suppression of sensory gating: Freedmanet al. 1987; Braff and Geyer 1990). Though the rates thatare relevant for natural language and the sensory gatingphenomenon obviously differ, it is possible that some typeof temporal sequencing disturbance may also influencereceptive language in schizophrenia.

Memory capacity. Individuals differ in the efficacyof their comprehension processes (Perfetti and Lesgold1977; Daneman and Carpenter 1980; King and Just 1991;Just and Carpenter 1992). A perspective that has provenuseful in accounting for this fact is the capacity theory, asdeveloped and refined by PA. Carpenter and M.A. Justand their colleagues. In a recent formulation, capacity rep-resents a composite of activation that is finite in extent,and mediates the storage and computations necessary forunderstanding linguistic constructions (see Miyake et al.1994; Haarmann et al. 1997). A distinction was also madebetween the capacity construct and traditional workingmemory and short-term storage concepts (e.g., Baddeley1986), with capacity viewed more generally as a resourcethat enables storage and computations of sentence repre-sentations at multiple levels (lexical, syntactic, semantic,thematic, referential). The general assumption underlyingthe present study design is broadly consistent with thisview. Supportive evidence includes findings that thecapacity construct, as denned by reading span, predictedcomprehension performance for college students (Dane-man and Carpenter 1983; Just and Carpenter 1992; Mac-Donald et al. 1992) and patients with schizophrenia (Con-dray et al. 1996). Moreover, central nervous systemfunction appears modulated by syntactic complexity, withmanipulations of syntactic structure producing systematicchanges in the amplitude of event-related potentials (Kingand Kutas 1995) and the pattern of neural activation infunctional magnetic resonance imaging (fMRI) (Just et al.1996).

Present Study. In an initial report (Condray et al. 1996),comprehension accuracy was compared between schizo-phrenia patients and normal controls as a function of syn-

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tactic complexity and presentation rate. The focus of thatinitial report was on the global sentential level: simpleversus subject-relative versus object-relative sentences.The present report represents a refinement and extensionof that earlier work and includes additional participants.In the present report, patients' receptive syntax was exam-ined through analyses of their understanding about "Whodid what to whom" in clauses with variable word orders,which presumably influence transformational operations.The association was also tested between psychologicalfunctions, including memory capacity, and comprehensionaccuracy about information in sentential clauses requiringtransformational operations.

MethodsParticipants. Study participants included 32 males diag-nosed with DSM-HI-R schizophrenia (APA 1987), and 22males diagnosed as no lifetime DSM-III—R Axis I or AxisII disorder (APA 1987). All study participants were evalu-ated with the Structured Clinical Interview forDSM-III-R (Spitzer et al. 1989). Normal control subjectswere additionally evaluated with the Personality DisorderExamination (Loranger 1988). Psychiatric diagnoses wereassigned during case conferences. General exclusion cri-teria were the following: first language other thanAmerican English, history of major medical or neurologi-cal disorders, Wechsler Adult Intelligence Scale-Revised(WAIS-R, Wechsler 1981) Verbal IQ < 85, and readinglevel < eighth grade as measured by the Wide RangeAchievement Test (WRAT). Schizophrenia patients wereexcluded if they met criteria for current substance use dis-order. Audiometric screening was conducted (both ears)using 500, 1,000, 2,000, and 4,000 Hz at 40 dBA SL. Allindividuals passed the screening except for one individualwho was able to detect further screening tones of 800 and1,500 Hz at 65 dBA SL.

Following explanation of procedures and prior to test-ing, all subjects provided written, informed consent to par-ticipate. Control subjects and outpatients were reimbursedfor study participation.

Evaluation of Sentence Processing. Sentence process-ing was evaluated using tests of sentence span memory,intelligibility of accelerated presentation rate, and sen-tence comprehension.

Sentence span memory. Memory span for sentence-length materials was evaluated with a modified aura! ver-sion of the Sentence Span Test developed by Leahy (1987)for use with clinical and general population individuals.The Sentence Span Test was based on the Reading Spantask developed earlier by Daneman and Carpenter (1980)for use with college students. The Sentence Span Test

measures memory for the final words in serial sentencesthat are presented in sets of sentences that graduallyincrease in size: 2 sets of 2 sentences each; 3 sets of 3 sen-tences each; 3 sets of 4 sentences each; 3 sets of 5 sen-tences each; 3 sets of 6 sentences each; 3 sets of 7 sen-tences each; and 1 set of 8 sentences. Sentence Span is thelargest set size for which all final words are recalled cor-rectly. Subjects were advised that they would hear a seriesof sentences after which they would be asked to recall thefinal word of each sentence in each set. They were alsoadvised to expect that the number of sentences wouldincrease as the test progressed.

Intelligibility of accelerated presentation rate. Anestimate of intelligibility for the accelerated presentationrate was obtained from the responses recorded to a sepa-rate set of 16 warm-up sentences presented at the acceler-ated rate (proportion of words repeated correctly). Asdescribed below (in Procedure section), the task was torepeat each warm-up sentence verbatim. Warm-up sen-tences were simple sentence constructions used in previ-ous work on the intelligibility of accelerated speech (Wal-lace and Koury 1981).

Sentence comprehension task. Two types of sen-tence processing demand were varied: syntactic and tem-poral. Syntactic demand was varied by contrasting sen-tence constructions that differed in grammatical structure,while holding the item load constant (i.e., all sentencescontained an equal number of words). Temporal demandwas varied using a conversational and an accelerated rate.Sentences and questions were presented aurally.

Syntactic structure. The focus of the present reportconcerns accuracy of understanding about the roles ofactor versus object as they were specified by the syntaxof the main and embedded relative clauses in subject-relative and object-relative sentences (i.e., "Who didwhat to whom?"). Three types of sentence constructionswere presented to all study participants: 16 object-rela-tive sentences, 16 subject-relative sentences, and 16simple declarative sentences. All sentences were 9words in length. All relative sentences contained twopast tense verbs, the majority (n = 53/64 = 83%) ofwhich were classified as transitive in their first or domi-nant meaning (Webster's 1979). Word order differsbetween the two types of relative sentences: the basicword order in English (SVO) is preserved in subject-rel-ative sentences, while the uncommon word order involv-ing objects preceding subjects (object subject verb[OSV]) occurs in object-relative sentences. The 48 sen-tences included items used by King and Just (1991, p.600) and items that were developed for the presentstudy. Examples of the relative sentences are

Object-relative: The reporter that the senator attackedadmitted the error.

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Subject-relative: The accountant that sued the lawyerread the paper.

Simple declarative sentences were SVO constructionsthat served as control items in earlier comparisons ofglobal sentence processing (Condray et al. 1996); forexample,

Simple declarative: The curator purchased the antiquebook for the museum.

Sentence comprehension questions. Relative sen-tences: Three Who questions immediately followed each rel-ative sentence to assess understanding of the facts and logi-cal relationships that were specified by the syntax. Forexample, recognizing that the initial noun plays dual roles(actor and object) is necessary for an accurate understandingof object-relative sentences. Thus, in the sentence "Thereporter that the senator attacked admitted the error," it isnecessary to understand that the reporter serves as the actorin the main clause ("The reporter . . . admitted the error"),and as the object of the action in the relative clause (". . .(that) the senator attacked"). The Who questions used toassess understanding of these relations were (1) "Whoadmitted the error?"—that is, Who did X? in the mainclause; (2) "Who was attacked?"—or, Who was done X? inthe relative clause; and (3) "Who did the attacking?"—or,Who did X? in the relative clause. Scoring was straightfor-ward, with a total possible of 96 correct: 32 sentences (16object-relative and 16 subject-relative) X 3 questions persentence. Simple declarative sentences: Three Wh- questions(Who? What? Where? and/or Whose?) followed each simpledeclarative sentence to assess understanding of the facts andrelationships described in the sentence. Scoring was straight-forward, with a total possible of 48 correct: 16 sentences X 3questions per sentence.

Presentation rate. Sentences were presented aurallyat two rates: conversational and accelerated. All sentencesand questions were recorded by a female speaker (nativeof western Pennsylvania) using her typical conversationalrate. The accelerated presentation rate was accomplishedusing a frequency-controlled technique. Frequency-con-trolled techniques of accelerating speech records havebeen demonstrated to produce superior intelligibility whencompared with frequency-shifted techniques (Wallace andKoury 1981). In the present study, the frequency-con-trolled technique increased the playback speed to approxi-mately twice that of the conversational rate without pro-ducing a linear increase in the frequency or pitch of thespeech record. A Media Vision sound board was used toproduce this accelerated rate. The sound board recorded16-bit samples at 44.1 kHz. The software application ran-domly sampled the original speech record digitally anddeleted half of the samples (50% compression).

Procedure. A PC-based computer was used to presentthe sentence and question stimuli. Subjects listened to the

language stimuli through AKG Acoustics K340 stereoheadphones. Prior to the test sentences, a separate set of 16warm-up sentences was presented at the accelerated rate.The task was to repeat each warm-up sentence verbatim.The purposes of this warm-up set were to accommodatesubjects to the rapid rate, and to obtain an estimate ofintelligibility for this presentation rate. Previous workshowed that college students accommodated to frequency-controlled speech after similar exposure (Wallace andKoury 1981). The 48 test sentences and comprehensionquestions immediately followed the warm-up sentences.

Each subject was presented with all 48 test sentences.Each of the three sentence types was presented under eachof the two presentation rates, with 8 sentences in each ofthe 6 combinations of sentence type and presentation rate.Sentences were assigned randomly to the two presentationrate conditions. The 6 sentence X rate combinations weredistributed evenly across the testing session in 8 blocksthat consisted of 6 sentences per block. Each block thusincluded one presentation of each sentence type X presen-tation rate condition. Assignment of sentences to blocksand presentation order of conditions within each blockwere also randomized. Comprehension questions werepresented at the conversational rate, and responses wererecorded by a research technician.

Data AnalysesPrimary Measures. The measures of primary interestincluded response accuracy in the Sentence Span Test, theIntelligibility task, and the Sentence Comprehensiontask—Relative Sentences. Response accuracy (numbercorrect) was converted to the proportion correct and thentransformed by the arcsine transformation prior to con-ducting the statistical tests (Fleiss 1986). Data values thatare presented in tables and graphs are proportions (excep-tion: Sentence Span data are presented as Span Set Size tofacilitate interpretation). However, all statistical analysesare based on the arcsine transformation of the proportionof correct responses. This strategy was used to adjust fordistributions associated with high accuracy rates that wereproduced by some of the tasks and experimental condi-tions, and to provide more conservative tests of the data.The experimental design for the Sentence Comprehensiontask was a mixed factorial that included both between-and within-subjects factors. Results were tested usinganalyses of variance (BMDP2V ANOVAs), with diagno-sis (two levels) as the between-subjects factor, and sen-tence complexity (two levels), presentation rate (two lev-els), and within-sentence clause (three levels) as thewithin-subjects factors. The Greenhouse-Geisser correc-tion was applied to analyses of the within-sentence clausevariable, and the epsilon factors for these adjustments are

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reported. The standard significance level of a = 0.05 wasused for the omnibus ANOVAs. Theoretically motivatedanalytical comparisons followed findings of significantresults in the omnibus ANOVAs (see Keppel 1991). Theseanalytical comparisons were evaluated at the more strin-gent significance level of a = 0.01 to reduce the risk oftype I errors that may accompany such comparisons(Keppel 1991). Trend significance for analytical compar-isons was set at a = 0.05.

Tests of Association. The association between languagecomprehension and other psychological functions wasexamined using linear regression analysis with simultane-ous entry of variables (SPSS 10.0). Unstandardized betasare reported to facilitate comparisons across samples(Pedhazur 1982). The association between language com-prehension and general intellectual ability (WAIS-R) wasexamined using standard tests of correlation (Pearson r).

Standard Residualized Scores. To remove extraneousvariance measured by the conditions of theoretical interest(relative clauses), standard residualized scores were com-puted in the manner recommended by Chapman andChapman (1989, p. 363) and entered as the measure ofindividual differences in an additional ANOVA: (1) foreach individual, the predicted scores on the relative clauseconditions (embedded—object and embedded—actor)were computed based on their observed main clausescore, using the regression equations for controls; (2) eachresidualized score was then standardized using the stan-

dard errors of controls' observed relative clause scores;(3) each individual's standard residualized scores (embed-ded—object and embedded—actor) were then enteredinto an ANOVA, with diagnosis (two levels) as thebetween-subjects factor and relative clause condition (twolevels) as the within-subjects factor.

ResultsCharacteristics of Sample. Table 1 presents the charac-teristics of the sample. Patients and controls did not differfor age, education, or single-word reading ability(WRAT). General verbal ability was assessed using thesubtests from the WAIS-R Verbal IQ. Compared to con-trols, patients were characterized by an uneven pattern ofperformance on these measures of verbal ability, with sig-nificant group differences observed only for theArithmetic and Comprehension subtests. (Data were miss-ing for one control on the Vocabulary subtest and onepatient on the Similarities subtest, which is reflected in thedegrees of freedom.) Handedness (Kutas and Van Petten1994) was assessed using items from the EdinburghHandedness Inventory (Oldfield 1971), and patients andcontrols showed a similar proportion of individuals with aright-hand preference.

Clinical Characteristics of Patients. This sample of 32schizophrenia patients included 17 inpatients and 15 out-patients who were receiving treatment in the VeteransAffairs Pittsburgh Healthcare System at the time of test-

Table 1. Characteristics of the sample

Age, mean (SD)Education (yrs), mean (SD)Single-word reading ability (WRAT),

mean (SD)Verbal ability (WAIS-R), mean (SD)

InformationDigit spanVocabularyArithmeticComprehensionSimilarities

Handedness, f (%)RightLeftBoth

Schizophrenia patients(n = 32)

42.4 (7.9)12.8(1.9)76.7 (7.4)

10.6(2.1)9.6 (2.4)9.9 (1.9)8.3 (2.4)8.2(2.1)9.2 (2.8)

29 (90.6)2 (6.3)1 (3.1)

Normal controls(/7=22)

38.9 (8.4)13.6(1.2)73.0 (9.2)

11.0(1.9)10.7(3.0)10.8(1.9)10.7(3.0)10.6 (2.3)10.2(2.4)

20 (90.9)1 (4.5)1 (4.5)

ftest

1.551.851.65

<11.491.623.163.971.30

df

525252

525251525251

P

0.130.070.11

0.420.140.110.0030.00020.20

Note.—SD = standard deviation; WAIS-R = Wechsler Adult Intelligence Scale-Revised; WRAT = Wide Range AchievementTest.

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ing. These patients were assigned the followingDSM-III-R schizophrenia disorder subtypes: undifferenti-ated (n = 12), paranoid (n = 6), and residual (/? = 11).Three patients were assigned the diagnosis of schizoaffec-tive disorder. Their clinical course of illness was charac-terized by a mean age of 24.6 years (standard deviation[SD] = 4.7; range: 15-34) at the time of first psychiatrichospitalization, an average illness duration of 18.2 years(SD = 6.7; range: 2-34), and a mean of 9.8 (SD = 6.9;range: 3-28) psychiatric hospitalizations.

Medication status of patients. Of the 32 patients, 18were receiving haloperidol and 14 were receiving otherantipsychotic medications (chlorpromazine, fluphenazine,loxapine, perphenazine, risperidone, thioridazine, thiothix-ene). Of these 32 patients, 29 were receiving oral antipsy-chotic medication at the time of study participation, andtheir mean daily dose in chlorpromazine equivalents(Appleton 1988) was 504.02 mg/day (n = 29; median =400; SD = 298.57; range: 50-1127.8); 1 patient wasreceiving oral risperidone (8 mg/day); and 2 patientsreceived injections of haloperidol decanoate (100mg/month and 125 mg/month, respectively) during themonth prior to study participation. Of the 32 patients, 20were additionally receiving adjunct anticholinergic med-ication (benztropine, mg/day: n = 20; mean = 2.75; median= 2; SD = 1.29; range: 1-6). (Seven of these 20 patientsreceiving anticholinergic medication were participating ina double-blind haloperidol maintenance and placeboreplacement protocol, in which adjunct anticholinergicmedication was discontinued 2 weeks prior to testing [seevan Kammen et al. 1996]). Finally, of the 32 patients, 13were receiving only antipsychotic and adjunct anticholin-ergic medications; the pharmacology treatment regimensof the remaining 19 patients involved a variety of addi-tional medications, including albuterol (n = 2); amitripty-line (n = 1); clonazepam (n = 2); desipramine (n = 2);diphenhydramine (n = 2); fluoxetine (n = 2); imipramine(n = 1); lithium carbonate (n = 6); lorazepam (n = 2); niza-tidine (n = 1); sertraline (n = 6); theophylline (n = 1); tra-zodone (n = 1); trihexyphenidyl (n = 1).

Sentence Processing. The measures of primary interestincluded response accuracy in the Sentence Span Test(largest set size possible = 8), the Intelligibility task (totalpossible =100 words), and the Sentence Comprehensiontask—Relative Sentences (total correct possible = 96).Response accuracy (number correct) for these primarymeasures was converted to the proportion correct and thentransformed by the arcsine transformation prior to con-ducting the statistical tests (Fleiss 1986). Data values thatare presented in tables and graphs are proportions (excep-tion: Sentence Span data are presented as Span Set Size tofacilitate interpretation); however, all statistical analyses

are based on the arcsine transformation of the proportionof correct responses.

Sentence span memory. Performance on the Sen-tence Span Test (set size) differed (Fj 52 = 11.45, p =0.001) between patients (mean/SD = 2.7/0.94) and con-trols (mean/SD = 3.5/0.80).

Intelligibility of accelerated presentation rate.Both diagnostic groups exhibited a high rate of intelligibil-ity for the individual words in sentences that were pre-sented at the accelerated rate used in the sentence compre-hension task: mean proportion of words repeated verbatimin the intelligibility task for patients (mean/SD =0.97/0.09) and controls (mean/SD = 0.99/0.01) did not dif-fer (F1 5 2 = 1.68, p = 0.20).

Sentence Comprehension PerformanceSimple sentences. The mean proportion of correct

responses to questions about the simple declarative sen-tences for each diagnostic group under each presentationrate condition were as follows: conversational rate(mean/SD), patients = 0.77/0.12, controls = 0.91/0.07;accelerated rate (mean/SD), patients = 0.75/0.14, controls= 0.87/0.06. Diagnosis and presentation rate influencedoverall understanding accuracy for simple sentences, andpatients and controls exhibited different patterns of accu-racy as a function of presentation rate. These results wereobtained as follows: Groups differed in their overall pro-portion of correct responses to questions about simple sen-tences (Fj 52 = 21.88, p < 0.001), with patients showingreduced accuracy compared to controls (76% vs. 89%,respectively). Presentation rate also influenced compre-hension accuracy (Ft 52 = 7.75, p < 0.01), with the conver-sational rate producing greater accuracy compared to theaccelerated rate (84% vs. 81%, respectively). The diagno-sis X rate interaction effect (Fl 52 = 4.71, p < 0.05) indi-cated that the two groups were characterized by differentpatterns of accuracy for simple sentences under the twopresentation rates. Analyses of the simple effects of pre-sentation rate on accuracy in each diagnostic groupshowed that rate influenced accuracy in controls (F( 21 =10.87, p < 0.01) but not in patients {p = 0.64).

Relative sentences. Table 2 presents the mean pro-portion of correct responses to Who questions for eachdiagnostic group under each relative sentence and within-sentence clause condition at each presentation rate.

Effects of linguistic structure and presentation rateon comprehension accuracy. Each of the factors of theo-retical interest exerted significant main effects on compre-hension accuracy. First, sentence complexity influencedcomprehension (F, 52 = 43.92, p < 0.001), with greaterresponse accuracy occurring for subject-relative sentences(84%) compared to object-relative sentences (73%).

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Table 2. Comprehension of relative sentences: Proportion correct responses to Who questions,mean (SD)

M a i n -Actor

Embedded—Object

Embedded—Actor

Schizophrenia patients (n = 32)Object-relative sentences

Presentation rateConversationalAccelerated

Subject-relative sentencesPresentation rate

ConversationalAccelerated

Normal controls (n = 22)Object-relative sentences

Presentation rateConversationalAccelerated

Subject-relative sentencesPresentation rate

ConversationalAccelerated

0.91 (0.13)0.69 (0.22)

0.88(0.16)0.92 (0.16)

0.95 (0.07)0.84(0.10)

0.95 (0.08)0.95 (0.09)

0.69 (0.25)0.53 (0.24)

0.75 (0.21)0.66 (0.23)

0.83(0.19)0.70 (0.25)

0.86(0.16)0.84(0.17)

0.57 (0.27)0.52 (0.24)

0.71 (0.19)0.73 (0.20)

0.77(0.19)0.73 (0.23)

0.89(0.15)0.93(0.11)

Note.—SD = standard deviation.

Second, type of within-sentence clause information alsoaffected comprehension (F2 104 = 73.60, p < 0.001,Greenhouse-Geisser e = 0.71). The highest rate of accu-racy occurred in response to questions concerning mainclause—actor information (89%), while a reduced andcomparable accuracy rate was associated with questionsabout the two types of embedded relative clauses: embed-ded—object (73%) and embedded—actor (73%). Pairwisecomparisons confirmed the statistical reliability of thesedifferences: main clause—actor versus embeddedclause—object (F, 53 = 84.82, p < 0.001); main clause—actor versus embedded clause—actor (Fj 53 = 87.45, p <0.001); embedded clause—object versus embeddedclause—actor (p = 0.66). Third, presentation rate addi-tionally influenced comprehension (Fj 52 = 19.06, p =0.0001), with the normal or conversational rate producinga higher rate of accuracy compared to the accelerated rate(81% and 76%, respectively).

To provide a more detailed understanding of the inter-action effect involving sentence complexity, presentationrate, and within-sentence clause (F2 104 = 10.93, p =0.0001, Greenhouse-Geisser e = 0.96), a set of theoreti-cally motivated simple interactions was conducted inwhich the joint effects of sentence complexity and presen-tation rate were examined under each level of within-sen-tence clause. Results indicate that the combined effects ofsentence complexity and presentation rate were influentialas a function of the type of clause information queried.Specifically, sentence complexity and presentation rate

exerted joint effects on understanding accuracy about"Who did X?" but not on accuracy about "Who was doneX?" These results were obtained as follows: The sentencecomplexity X presentation rate interaction was significantfor accuracy about main clause—actor information (Fj 53

= 52.72, p < 0.001) and embedded clause—actor informa-tion (Fj 53 = 10.33, p = 0.0022) but not for accuracy aboutembedded clause—object information (p = 0.13).

Effects of linguistic structure and presentation rateon comprehension accuracy in schizophrenia. Patientsand controls differed in their overall proportion of correctresponses (Fj 52 = 14.45, p = 0.0004), with patientsexhibiting reduced comprehension accuracy compared tocontrols (71% vs. 85%, respectively). More important, thediagnosis X within-sentence clause interaction effect(F2,i04 = 7-27> P = 0 0 0 4 ' Greenhouse-Geisser e = 0.71)indicates that patients and controls were characterized bydifferent patterns of accuracy across the various types ofwithin-sentence clause structures. This two-way interac-tion is presented in figure 1. None of the other interactionsinvolving the diagnostic group factor reached statisticalsignificance.

Two sets of simple effects were tested to locate thesource of the significant diagnosis X within-sentenceclause interaction reported above. These analyses identi-fied a group difference in the comparative levels of accu-racy for information contained in main versus relativeclauses. In both groups, the highest response accuracy wasobserved for information described in main clauses, com-

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Figure 1. Mean percent correct responses to Who questions about the information described in thesentential clauses of relative sentences in schizophrenia patients (n = 32) and normal controls (n = 22)(± standard error of the mean)

• Controls

• Patients

Main-Actor Embedded-Object Embedded-Actor

pared to information contained in embedded relativeclauses, while similar rates of accuracy occurred for thetwo types of relative clauses. However, patients showed anaverage decrement of 20.5 percent in their accuracy aboutembedded clause information, compared to their accuracyabout main clause information. In contrast, controlsshowed an average decrement of only 10 percent in theiraccuracy about embedded clause information, comparedto their accuracy about main clause information. Theseresults were obtained as follows: First, analyses of thesimple effects of within-sentence clause on response accu-racy in each diagnostic group showed a main effect ofclause in both patient and control groups: patients (F2 62 =87.27, p < 0.001, Greenhouse-Geisser e = 0.69); controls(F2 4 2 = 13.87, p = 0.0004, Greenhouse-Geisser e = 0.64).Moreover, pairwise comparisons of the various clausetypes showed a similar pattern in each diagnostic group:main clause—actor versus embedded clause—object(patients: F, 31 = 99.26, p < 0.001; controls: Fj 21 = 14.98,p = 0.0009); main clause—actor versus embeddedclause—actor (patients: F, 31 = 98.59, p < 0.001; controls:F[ 2i = 16.01, p - 0.0006); and embedded clause—objectversus embedded clause—actor (patients: p = 0.03; con-trols: p = 0.09). Second, analyses of the simple effects ofdiagnosis on the response accuracy associated with each

clause type showed that accuracy for embedded clauseinformation differed between the two groups: embeddedclause—object in patients versus controls: Fj 52 = 10.09, p= 0.0025; embedded clause—actor in patients versus con-trols: F, 52 = 21.86, p < 0.001. In contrast, the effect ofdiagnosis on the accuracy rate for main clause—actorinformation reached only trend significance (p = 0.04).

Standard residualized scores. To remove extraneousvariance measured by the within-sentence clause condi-tions of theoretical interest (relative clauses), standardresidualized scores (Chapman and Chapman 1989) wereused as the measures of individual differences (see DataAnalyses section): patients: Membedded_object = -0.58, SD= 0.64; Me m b e d d e d_a c t o r = -0 .89, SD = 0.92; controls:Membedded-^bject = 0.0000, SD = 0.98; Membedded_actor =0.0008, SD = 0.98. ANOVA results were consistent withfindings based on the conventional analyses: patients andcontrols differed in overall accuracy (F, 52 = 10.02, p =0.003); type of relative clause information (embedded—actor vs. embedded—object) influenced performanceaccuracy (F, 52 = 5.49, p = 0.023); and the diagnosis Xwithin-sentence clause interaction effect (Fj 52 = 5.56, p =0.022), which indicated that patients and controls werecharacterized by different patterns of accuracy for the twotypes of relative clause information.

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Association Between Language ComprehensionAccuracy and Capacity. The association between com-prehension accuracy and the psychological functions oftheoretical interest was tested using linear regressionanalysis. The two diagnostic groups were combined forthese analyses (n = 54). This relationship was examinedseparately for three dependent variables that involvedcomprehension accuracy for each type of sentential clause(main and embedded) and word order (SVO and OSV).Main clauses from the two types of relative sentences(subject- and object-relatives) represented an SVO wordorder, and they were combined for the analyses.Embedded clauses were examined separately based on thetype of relative-clause word order: the SVO order of sub-ject-relative sentences, and the OSV order of object-rela-tive sentences. Thus, comprehension accuracy wasdenned as the number of correct responses to Who ques-tions about the information contained in main clauses ofboth subject-relative and object-relative sentences (totalpossible correct = 32); embedded relative clauses of sub-ject-relative sentences (total possible correct = 32); andembedded relative clauses of object-relative sentences(total possible correct = 32). Two models were tested thatinvolved different sets of psychological functions as theindependent variables, which were selected and organizedbased on (1) the theoretical rationale outlined in thePsychological Functions section; and (2) collinearityissues (absence of correlations between independent vari-ables in the present sample). Model 1: The independentvariables for Model 1 were age (control variable), digitspan (WAIS-R subtest score), and memory span for sen-tences (Sentence Span Test score). Results in table 3 indi-

cate an association between comprehension accuracy andthese psychological functions in this sample. Model 1accounted for 20 percent of the variance associated withresponse accuracy for information in the embeddedclauses of subject-relative sentences (SVO word order),and 23 percent of the variance associated with responseaccuracy for information in the embedded clauses ofobject-relative sentences (OSV word order). The variablesin Model 1 were not successful in predicting accuracyabout main clause—information. Model 2: Because ofcollinearity issues, the control variable, age, was replacedby education in Model 2. The independent variables forModel 2 were education, vocabulary (WAIS-R subtestscore), and intelligibility. (Note that analyses for Model 2are based on 53 subjects because of missing data for 1normal control for the vocabulary measure.) Results intable 4 show an association between comprehension accu-racy and this set of psychological functions in this sample.Model 2 accounted for 32 percent of the variance associ-ated with response accuracy for information contained inthe main clauses of relative sentences (SVO word order);32 percent of the variance associated with response accu-racy for information contained in the embedded clauses ofsubject-relative sentences (SVO word order); and 39 per-cent of the variance associated with response accuracy forinformation contained in the embedded clauses of object-relative sentences (OSV word order).

The association between language comprehensionand general intellectual ability (WAIS-R IQ) was exam-ined using standard tests of correlation (Pearson r) con-ducted separately for the two diagnostic groups. Results intable 5 show that general intellectual functioning was not

Table 3. Association between psychological functions and comprehension accuracy for information insentential clauses (n = 54)

R2 Adj. R2 F ratio df beta SE beta f test

Main clauses: SVO 0.11 0.05Predictor variablesAgeDigit spanSentence span memory

Embedded relative clauses: SVO 0.25 0.2Predictor variablesAgeDigit spanSentence span memory

Embedded relative clauses: OSV 0.28 0.23Predictor variablesAgeDigit spanSentence span memory

1.99

5.51

3,50 0.13

3,50 0.002

6.37 3,50 0.001

-0.00110.01790.338

-O.00450.0170.968

-0.00870.03280.719

0.0040.0120.234

0.0050.0150.296

0.0050.0150.299

<—11.541.45

< - 11.163.28

-1.812.212.4

0.770.130.15

0.350.250.002

0.080.0320.02

Note.—adj. = adjusted; OSV = object subject verb; SE = standard error; SVO = subject verb object.

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Table 4. Association between psychological functions and comprehension accuracy for information insentential clauses (n = 53)

Adj. R2 F ratio df beta SE beta t test

9.26 3,49 0.001

Main clauses: SVO 0.36 0.32 9.09 3,49 0.001Predictor variables

Education (yrs)VocabularyIntelligibility

Embedded relative clauses: SVO 0.36 0.32Predictor variables


Embedded relative clauses: OSV 0.42 0.39 11.92 3,49 0.001Predictor variables


0.03830.02280.594

0.05180.05630.563

0.04430.05920.794

0.0150.0140.158

0.0210.0180.216

0.020.0180.212

2.521.693.76

2.493.042.6

2.173.263.74

0.020.10.001

0.020.0040.012

0.040.0020.001

Note.—adj. = adjusted; OSV = object subject verb; SE = standard error; SVO = subject verb object.

Table 5. Correlations between WAIS-R scores and language comprehension accuracy

VerbalIQ

PerformanceIQ

Full-scaleIQ

Schizophrenia patients (n = 32)Relative sentences

Main clausesEmbedded—objectEmbedded—actor

Total correctSimple and relative sentences

Normal controls (n = 22)Relative sentences

Main clausesEmbedded—objectEmbedded—actor

Total correctSimple and relative sentences

0.240.290.27

-0.26-0.050.002

0.040.170.18

0.28 -0.09 0.15

0.300.52*0.57"

0.140.56**0.38

0.260.580.53

0.60** 0.47* 0.59*

Note.—WAIS-R = Wechsler Adult Intelligence Scale-Revised.* p < 0.05, 2-tailed; ** p < 0.01, 2-tailed

significantly associated with language comprehensionaccuracy for schizophrenia patients. In contrast, generalintellectual functioning was strongly and significantly cor-related with language comprehension accuracy for normalcontrols.

DiscussionThe present study addresses an unresolved question in theliterature: whether receptive syntax is intact in schizophre-nia. Results showed that patients and controls differed in

their overall comprehension accuracy about relative sen-tences, with patients exhibiting a mean reduction of 14percent in their overall accuracy, compared to controls.More important, patients and controls differed in their pat-tern of accuracy, and this pattern was a function of syntac-tic structure. Patients showed an average decrement of 20percent in their accuracy about "Who did X?" and "Whowas done X?" in relative clauses, compared to their accu-racy about actors in main clauses. In contrast, controlsexhibited an average decrement of only 10 percentbetween relative and main clause information. Patients

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and controls did not show different patterns of accuracyfor information in relative sentences as a function of pre-sentation rate, although this finding may be due to ceilingeffects for the rate factor. For example, it is possible thateven further increases in temporal demand (e.g., deletionof > 50% of the speech sample) would result in a differentpattern of effects of presentation rate on understandingaccuracy about relative sentences for patients versus con-trols. Indeed, the effects of presentation rate on languageunderstanding in schizophrenia disorder may be complex,as seen in the significant diagnostic group X presentationrate interaction obtained for simple sentence construc-tions, with controls showing a greater reduction in accu-racy between the slow versus fast rates, compared topatients. There are at least two possible interpretations ofthe diagnostic group X presentation rate interaction forsimple sentences: (1) the faster presentation rate may haveassisted patients in maintaining context for the simple sen-tence constructions; or (2) the accelerated rate may havebeen more disruptive to the understanding of simple sen-tences at higher levels of performance accuracy; that is,controls' greater reduction in accuracy for simple sen-tences at the accelerated rate may have been due to theirhigher overall accuracy about simple sentences (89%)compared to patients' overall accuracy about simple sen-tences (76%). Finally, comprehension accuracy was corre-lated with functioning in the domains of memory, seman-tic knowledge, and temporal auditory processing.

The present findings provide a refinement of the pre-vious literature, in which it had been shown that patientsare sensitive to syntactic structure (Rochester et al. 1973;Carpenter 1976; Grove and Andreasen 1985) but are char-acterized by reduced comprehension for grammaticallycomplex sentences (Morice and McNicol 1985; Condrayet al. 1992; Condray et al. 1996). Consideration of thepresent data, however, must include recognition of certaininterpretive challenges. An important qualification per-tains to how receptive syntax function is formulated, witha crucial question concerning which functional compo-nents are entered into the model. It is generally assumedthat receptive syntax involves multiple functional compo-nents. It is therefore possible that an increase in syntacticcomplexity may merely burden further cognitive functionsthat are commonly deployed across a broad range of infor-mation processing tasks (e.g., the holding online of incom-ing information in short-term storage, the accessing oflong-term memory and semantic knowledge networks, therapid processing of sequential stimuli). Thus, one interpre-tation is that a generalized cognitive deficit (Chapman andChapman 1989)—in combination with variations in taskstructure, complexity, or both—produced the more precip-itous decline in patients' receptive syntax function in thepresent study. It is also possible, however, that increased

syntactic complexity requires the involvement of one ormore additional functional components (e.g., transforma-tion operations such as movement). An alternative expla-nation, therefore, is that disturbances in specific compo-nents of receptive syntax function may be responsible forpatients' reduced understanding accuracy about grammati-cally complex constructions; for example, a disturbance intransformational operations, such as syntactic movement,produced difficulty in connecting "Who" with "did X"versus "was done X." It is important to emphasize thatthese two accounts do not represent mutually exclusivealternatives, with combinations of the logic yielding addi-tional, equally viable explanations; for example, a unique,specific deficit in function(s) used in linguistic analysesthat is superimposed on the generalized cognitive defi-ciency. The two accounts are also not exhaustive. As anadditional consideration, performance accuracy may havereflected a methodology confound whereby accuracy wasinfluenced by an interaction of memory function andwithin-sentence word order. Specifically, the ordering ofmain and embedded relative clauses in both types of rela-tive sentences is such that the pattern of accuracy couldmerely reflect a primacy-recency effect (Underwood et al.1978), with accuracy a function of the position held by theclause within the sentence. As a result, greater accuracywould be expected for information in initial and last posi-tions (main clauses), compared to the level of accuracy forinformation occupying the middle positions (relativeclauses). All of these possibilities require empirical test-ing.

Of interest, the proportion of variance in comprehen-sion accuracy that was accounted for by selected cognitivefunctions ranged from 20 percent to 39 percent. This pat-tern suggests that receptive syntax function includes, but isnot fully explained by, an online interface with cognitivefunctions such as memory, semantic knowledge, and tem-poral auditory processing. Such an interpretation is consis-tent with a modularity formulation (Fodor 1983), as wellas with recent formulations of cognitive function as adynamic and distributed process (see Carpenter et al.2000). It is important to recognize, however, that the cor-relation data from the present study must be qualified bycertain limitations: (1) the cognitive measures employedare not absolute and (2) the model is not exhaustive (e.g.,potential specification errors, see Pedhazur 1982). Finally,general intellectual ability (WAIS-R scores) was associ-ated with language comprehension accuracy in normalcontrols. In contrast, general intellectual ability (WAIS-Rscores) was not significantly correlated with languagecomprehension accuracy in schizophrenia patients. Thislatter pattern may indicate that receptive syntax dysfunc-tion in schizophrenia is not associated with compromisedgeneral cognitive ability.

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A final consideration concerns the effects on memoryof the pharmacological agents used to treat the schizophre-nia patients in the present study. Findings of recent clinicaland nonhuman primate studies suggest that working mem-ory is influenced by agents associated with antagonism ofdopamine D2 receptors; specifically, verbal working mem-ory in schizophrenia patients was influenced by such med-ications (Green et al. 1997; for a review, see Meltzer andMcGurk 1999), and impairment of working memory func-tion in adult monkeys was produced by chronic adminis-tration of haloperidol (Castner et al. 2000). If memorycapacity does influence receptive syntax function, thenadministration of neuroleptic medications may have influ-enced patients' syntax processing.

In summary, findings from the present study suggestthe hypothesis that receptive syntax operations are dis-rupted in schizophrenia, and this disturbance may not becompletely explained by compromised general cognitiveability.

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Medical Center. Valuable comments were provided aboutthe manuscript by Angela G. Glasgow, D.V.M., Mary E.Kelley, M.S., and four anonymous reviewers.

Acknowledgments

This research was supported by the National Institute ofMental Health (MH50631) and the Medical Research Ser-vice of the Department of Veterans Affairs. The authorsthank the patients for their participation in this study.William H. Broadley IV developed the computer softwarefor the presentation of the language stimuli and the produc-tion of the accelerated rate in the sentence processing exper-iment. Consultation regarding the psychiatric diagnoses ofstudy participants was provided by George G. Dougherty,Jr., M.D., John A. Gurklis, M.D., and the clinical staff of theSchizophrenia Research Unit at the Highland Drive VA

The Authors

Ruth Condray, Ph.D., is Assistant Professor of Psychiatry,and Stuart R. Steinhauer, Ph.D., is Research AssociateProfessor, University of Pittsburgh School of Medicine,Pittsburgh, PA. Daniel P. van Kammen, M.D., Ph.D., isDirector, Global Clinical Research and Development,Robert Wood Johnson Pharmaceutical Research Institute,Raritan, NJ; Professor Emeritus, University of PittsburghSchool of Medicine; and Adjunct Clinical Professor, Uni-versity of Pennsylvania, Philadelphia, PA. Annette Kas-parek, B.S., is Senior Research Associate, University ofPittsburgh Medical Center, Pittsburgh, PA.

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Documents

The Language System in Schizophrenia: Effects of Capacity and