conceptual combination in schizophrenia: contrasting property and relational interpretations

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Journal of Neurolinguistics 20 (2007) 92–110

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Conceptual combination in schizophrenia:Contrasting property and relational interpretations

Debra Titonea,�, Maya Libbena, Meg Nimanb,Larissa Ranbomb, Deborah L. Levyb

aDepartment of Psychology, McGill University, Stewart Biology Building, 1205 Dr. Penfield Ave.,

Montreal, QC, Canada H3A 1B1bPsychology Research Laboratory, McLean Hospital, Harvard Medical School, Boston, MA, USA

Received 5 June 2006; accepted 8 June 2006

Abstract

This study employed a conceptual combination task based on Estes and Glucksberg [(2000).

Interactive property attribution in concept combination. Memory & Cognition, 28(1), 28–34] to

address the question of whether semantic processing abnormalities in schizophrenia arise from

deficits in semantic storage or access, or the controlled use of semantic memory representations. High

thought disorder schizophrenia patients (n ¼ 25), low thought disorder schizophrenia patients

(n ¼ 22), and controls (n ¼ 25) read and interpreted noun–noun combinations that varied with

respect to whether the modifier noun had a salient semantic feature that could be mapped to a

relevant dimension of a head noun. The percentages of property attributions, relational

interpretations, and ‘‘other’’ interpretations were determined for each combination type. Subjective

difficulty ratings were also collected for each response. Neither high nor low thought disorder

patients differed from controls in the production of property interpretations. High thought disorder

patients were significantly less likely to generate relational interpretations and significantly more

likely to generate ‘‘other’’ interpretations. Subjective difficulty ratings were low for all groups,

suggesting that differences in the ease of generating interpretations does not account for the

results. The finding of intact property interpretations suggests that the integrity and initial access of

semantic memory is spared in schizophrenia. In contrast, the reduced production of relational

interpretations and increased production of ‘‘other’’ interpretations in schizophrenia suggests a

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ARTICLE IN PRESSD. Titone et al. / Journal of Neurolinguistics 20 (2007) 92–110 93

compromised ability to engage in the controlled processing operations necessary to make flexible use

of semantic material.

r 2006 Elsevier Ltd. All rights reserved.

Keywords: Schizophrenia; Semantics; Language; Conceptual combination

Many neurocognitive systems have been implicated in schizophrenia (SZ), butdisturbances in cognition and semantic processing are predominant features of thedisorder (Bleuler, 1911/1950; Kraepelin, 1919/1971). Consider, for example, the responseof an individual diagnosed with SZ when asked to state what card VIII of the Rorschachlooks like: ‘‘Oh man, this is out of sight. This is like a couple of y panther cats who are pink

in color, who arey engaging upony some kind ofy kinghoody of a great ship, a great

bar–, a greaty fishy who rules the sea, and theny he’s sailing, he’s sailing, and yet he

usesy his great umy panthersy to show forth the fact thaty he comes in peace, and that

he, hey he is, he isy and he’s issuing forthy a stalwarty peaceability that... that no one

can put asunder in any way, shape or form, an’ he’s just happy an’ free, an’ he’s kinday got it

all together, an’ he knows it.’’ In the Thought Disorder Index (TDI) scoring scheme(Johnston & Holzman, 1979; Solovay et al., 1986), this response includes several instancesof idiosyncratic use of language (in bold) and the entire response would be scored as aconfabulation (finding relationships between unrelated percepts and embellishing them inan unrealistic way) (Shenton, Solovay, & Holzman, 1987; Solovay, Shenton, & Holzman,1987; Spohn et al., 1986). Tangentiality, derailment, poverty of amount and content ofspeech, illogicality, and incoherence also characterize aspects of schizophrenic thoughtdisorder (Andreasen, 1979; Barch & Berenbaum, 1996; Docherty, Cohen, Nienow, Dinzeo,& Dangelmaier, 2003; Harrow, Marengo, &McDonald, 1986). Thought disorder in SZ hasbeen linked to impaired structure and function of the superior temporal lobe (Kircher etal., 2001; Shenton et al., 1992), and to impaired executive functions such as contextprocessing and interference resolution (Kerns & Berenbaum, 2002, 2003).

Although thought disorder is not expressed exclusively through language (for example,certain behaviors may be based on delusional ideas), spoken or written language is themost common medium for conveying disturbances in thinking. In our view, the thinkinganomalies associated with psychotic conditions are not, fundamentally, speech or languagedisorders (for a more detailed discussion see Holzman, Levy, & Johnston, 2005; Holzman,Shenton, & Solovay, 1986; Makowski et al., 1997). Rather, when language is used in anidiosyncratic way, it represents the outcome of a deviant thought process. The recognizablemeaning of the word or phrase does not fit the context and therefore obscures the meaningintended by the speaker, for example—‘‘a tree head kind of person’’, ‘‘posteriorpronunciations’’, ‘‘adhesive adjunctive extensions’’, ‘‘a non-verbal misrepresentation ofan unformulated thought.’’ Deviant verbalizations are a predominant characteristic of thethought disorder associated with SZ, and they are present in patients independent ofseverity of clinical state, indicating that they are a trait characteristic of schizophrenicthought disorder (Johnston & Holzman, 1979; Solovay, Shenton, & Holzman, 1987;Spohn et al., 1986).

In addition to thinking disturbances expressed in language production, SZ patients alsoshow semantic processing abnormalities in language comprehension (Bagner, Melinder, &Barch, 2003; Condray, Steinhauer, van Kammen, & Kasparek, 2002; Kostova, Passerieux,

ARTICLE IN PRESSD. Titone et al. / Journal of Neurolinguistics 20 (2007) 92–11094

Laurent, & Hardy-Bayle, 2003; Ruchsow, Trippel, Groen, Spitzer, & Kiefer, 2003;Salisbury, Shenton, Nestor, & McCarley, 2002; Sitnikova, Salisbury, Kuperberg, &Holcomb, 2002; Titone, Holzman, & Levy, 2002; Titone & Levy, 2004; Titone, Levy, &Holzman, 2000). Some investigators have attributed these abnormalities to disorganized ordamaged semantic memory representations or to interference with initial access to theserepresentations (Aloia et al., 1998; Aloia, Gourovitch, Weinberger, & Goldberg, 1996;Chen Wilkins, & McKenna, 1994; Elvevag et al., 2002; Goldberg et al., 1998; McKay et al.,1996). In this conceptualization, semantic memory representations and initial accessprocesses tend to be grouped as a general capacity for storing semantic material andgaining initial access to this material in an automatic or reflexive way. Other findings,however, suggest that semantic memory representations and initial access to them areintact in SZ, but the flexible use of semantic memory through more deliberate controlledprocessing operations is deficient (Chenery, Copland, McGrath, & Savage, 2004; Condray,Siegle, Cohen, van Kammen, & Steinhauer, 2003; Kerns & Berenbaum, 2002; Nestor et al.,2001; Sitnikova et al., 2002; Titone et al., 2002, 2000; Titone & Levy, 2004). Consistentwith the latter view, work from our group has found that SZ patients are impaired onlywhen the specific language comprehension situation is ambiguous and the flexible use ofsemantic memory requires inhibiting contextually irrelevant material. In contrast, whenthe language comprehension context requires only automatic retrieval of semantic memory(or lexical) representations, semantic processing is normal (Titone et al., 2000, 2002; Titone& Levy, 2004).The present study extends our work by examining patient performance on a task that

involves the comprehension of ambiguous multi-word sequences: novel conceptualcombinations (e.g., ‘‘zebra bag’’). Novel conceptual combinations are ubiquitous inlanguage, and they normally elicit consistent and plausible interpretations, despite the factthat they afford several plausible (and implausible) interpretations. How this process isnormally accomplished has been widely studied (Bock & Clifton Jr., 2000; Costello &Keane, 2001; Estes & Glucksberg, 2000; Gagne, 2002a; Glucksberg & Estes, 2000; Medin& Rips, 2005; Medin & Shoben, 1988; Murphy, 2002; Wisniewski & Murphy, 2005) andcan increase our understanding of the nature of semantic deficits observed in individualsdiagnosed with SZ.Individuals who are fluent in a language usually generate one of two types of

interpretations when faced with novel conceptual combinations (Medin & Rips, 2005;Murphy, 2002). The simplest type of interpretation is a property attribution, in whichsome conceptual feature of the modifier noun is automatically activated during lexicalretrieval and then is attributed to the head noun. In the combination ‘‘zebra bag’’, forexample, a salient conceptual feature of the modifier noun, zebra, is having stripes. Thisfeature is then attributed to the head noun bag, resulting in the interpretation, a striped

bag. Another common type of interpretation is a relational interpretation. Here, themodifier noun is linked to a thematic or functional role of the head noun, for example, thenotion that a bag is normally carried by an animate agent. For example, zebra bag isinterpreted as a bag that a zebra carries, most likely on its back. Other kinds ofinterpretations of conceptual combinations occur: hybridization (e.g., a robin canary is across between a robin and a canary) and construal (e.g., a plastic truck is a toy). In thepresent study we focus on property and relational interpretations, because they are themost frequent and best understood kinds of interpretations generated for novelnoun–noun combinations.


The factors that lead comprehenders to preferentially generate property or relationalinterpretations have been studied by several groups. Wisniewski and colleagues(Wisniewski, 1997, 1998, 2000) found that noun–noun combinations, in which modifiernouns are similar to head nouns, lead to property interpretations more frequently than torelation interpretations (e.g., tiger panther as a panther with a black and orange pattern).This ‘‘similarity effect’’ may arise because it is easier to identify differences betweentwo similar concepts, and thus to discover the specific properties to be mapped (althoughsee Gagne, 2000 for an alternative explanation of this effect). These findings were laterrefined to show that property attributions are more likely, and relational interpreta-tions less likely, under two conditions: (1) when a modifier noun has a salient featurethat can be attributed to a head noun, and (2) when a head noun has a relevant dimensionto receive that property mapping (Estes & Glucksberg, 2000). For example, the modifiernoun of the combination ‘‘zebra bag’’ has a salient feature (e.g., black and white stripes)and the head noun has a relevant dimension for accepting the mapping from thatfeature (e.g., an important dimension of bags is their appearance). Combinations ofthis type were termed high–high (HH), because they have a high salient feature as wellas a highly relevant dimension. In the combination ‘‘zebra trap’’, in contrast, the modifiernoun has the same salient feature, but the head noun does not have a relevant dimen-sion for that salient feature. Such combinations are termed high–low (HL). In thecombination ‘‘donkey trap’’, the modifier noun does not have a clearly salient featurethat is relevant to the head noun and the head noun does not have a relevant dimensionwith respect to the modifier noun. Such combinations are termed low–low (LL). Estesand Glucksberg (2000) found that 79% of university students generated propertyattribution interpretations for HH combinations such as zebra bag, whereas 23%and 16% of students produced property interpretations for zebra trap (HL) anddonkey trap (LH), respectively. The HL and LH combinations were presumed to berelational interpretations, but only property interpretations were actually scored. Thus,non-property interpretations may have been composed of relational interpretations or‘‘other’’ types.

The Estes and Glucksberg (2000) study is relevant to this study because it showsthat there is a clear normative pattern for conceptual combinations comprised ofequally dissimilar nouns that bias interpretations toward or away from propertyinterpretations. The biasing effect of property and relational interpretations may help tounderstand the nature of semantic dysfunction in SZ. In property interpretations of theHH variety, the modifier noun possesses a highly salient feature that can be readilymapped onto a highly relevant dimension of the head noun. The mapping process placeslittle demand on post-retrieval selection processes because the most readily activatedfeatures of the two nouns select for the property interpretation. For example, in thecombination zebra bag, a highly salient feature of zebra is that it has stripes. Since bag is anoun for which appearance is an important semantic dimension, interpretation of thiscombination as a striped bag is relatively easy to accomplish. Indeed, propertyinterpretations elicited by these types of combinations require only semantic access tothe meanings of the modifier and head nouns. In contrast, relational interpretationsrequire access both to semantic meaning and to post-retrieval selection processes becauseany two nouns possess a greater variety of relational linkages than property attributionsalone can accommodate. The demands associated with a relational interpretation fordonkey bag, a LH combination, are less automatic. Here, the semantics of donkey do not


readily constrain mapping to bag to give rise to a property interpretation. Rather, theybias toward a relational interpretation, because the range of plausible relationalinterpretations for donkey bag offers many choices (e.g., a bag carried by a donkey;a bag carrying donkey food; a bag that has a picture of a donkey; a bag made fromdonkey hide, etc.). Thus, compared with the easily generated property interpretation forzebra bag, a single relational interpretation for donkey bag requires additional post-retrieval selection.If deficits in the integrity of semantic knowledge are a primary feature of SZ, patients

should show comparable reductions in both property and relational interpretations, and acorresponding increase in ‘‘other’’ non-classifiable interpretations. Both property andrelational interpretations require, at a minimum, that comprehenders activate meaningsassociated with each modifier and head noun. If the integrity of semantic knowledge iscompromised, or if initial semantic access does not function properly, both property andrelational interpretations would be compromised. In contrast, if both the integrity ofsemantic knowledge and immediate lexical-semantic retrieval are intact, interpretationsthat rely on property attributions should remain intact. However, if only an ability to usesemantic knowledge in a flexible or controlled way at the post-retrieval stage is impaired,then responses that rely on relational interpretations ought to be impaired, because initialsemantic access of word meanings is necessary but not sufficient for generating relationalinterpretations. Post-retrieval selection processes would also be necessary to select for oneof a variety of plausible relational interpretations. Therefore, if only post-retrieval selectionmechanisms are impaired, but property interpretations are unaffected, the ability togenerate a relational interpretation would be reduced, resulting in an increase in ‘‘other’’interpretations.We conducted a version of Estes and Glucksberg’s (2000) conceptual combination

task with three participant groups: (1) individuals diagnosed with SZ with low amountsof thought disorder as measured by the TDI (SZ Low TDI), (2) individuals diagnosedwith SZ with high amounts of thought disorder (SZ High TDI), and (3) individualswho were not diagnosed with a psychiatric illness (Controls). Our version differedfrom that of Estes and Glucksberg in two ways. First, in addition to collecting infor-mation about the kinds of interpretations generated by these groups, we asked partici-pants to evaluate how difficult it was to generate each interpretation to determine whetherany group differences in comprehension were associated with differences in subjectiveeffort. Second, we affirmatively scored property, relational, and ‘‘other’’ interpretations,whereas only property interpretations were affirmatively scored in the Estes andGlucksberg study.Comparing patients with low and high amounts of thought disorder is important for two

reasons. First, patients diagnosed with psychiatric conditions of any kind are more likelyto show increased variability and poorer performance on tests of cognitive function. Thus,segregating patients according to a highly relevant clinical feature of the illness allows us totest hypotheses that are more specific to SZ and to partially control for factors that mayrelate to differences between patients and controls, such as medication, severity of illness,and poorer overall social functioning. Second, a number of studies have comparedlanguage-based cognitive dysfunction in patients with differing amounts of thoughtdisorder (Barrera, McKenna, & Berrios, 2005; Kerns & Berenbaum, 2002, 2003; Leeson,Simpson, McKenna, & Laws, 2005). Thus, the results may be linked to this larger bodyof work.


1. Methods

1.1. Participants

The patients (n ¼ 47) were outpatients who met DSM-IV criteria for a diagnosis of SZor schizoaffective disorder. Clinical assessments of the patients were conducted byexperienced interviewers and diagnosticians independently of the experimental tasks.Consensus diagnoses were assigned by four senior clinicians on the basis of a review of astandardized interview (Structured Clinical Interview for the DSM-IV) (Spitzer, Williams,Gibbon & First, 1994), an interview narrative, and a review of all available hospitalrecords, permitting both a cross-sectional and longitudinal evaluation. The non-psychiatriccontrol (NC) participants (n ¼ 25) were recruited from a medical outpatient clinic and theMcLean Hospital staff. The following inclusion criteria applied to all participants: nativeEnglish speaker, no diagnosed organic brain disease, no substance/alcohol abuse/dependence within the past two years, no tardive dyskinesia, no use of alcohol orrecreational drugs within two weeks of testing, and an estimated verbal IQ of at least 85.Written informed consent was obtained from all participants.

Thought disorder was assessed using the TDI (Coleman, Levy, Lenzenweger, &Holzman, 1996; Johnston & Holzman, 1979; Shenton et al., 1987; Shenton, Solovay,Holzman, Coleman, & Gale, 1989; Solovay et al., 1987). Responses and inquiry to a 10-card Rorschach were tape recorded and transcribed verbatim. Consensus TDI scores wereassigned blind to group and performance on the experimental task by a group of threeexpert scorers. In this study, we used the total TDI score as a measure of the quantity offormal thought disorder. The patient sample was divided into two groups based on theirtotal TDI score. The cut-off for assigning patients to the SZ High TDI and SZ Low TDIgroups was a total TDI score of 12.0, which resulted in 25 patients being assigned to the SZHigh TDI group and 22 patients being assigned to the SZ Low TDI group. This cut-offwas based on the overall distribution of TDI scores in the patient sample and a naturalbreak in the distribution that would result in an approximately equal number of patientsper subgroup. Table 1 presents demographic and clinical information about the groups.The groups did not differ in age, estimated verbal IQ (Wechsler, 1981), or years ofeducation. Both patient groups had a significantly lower level of functioning as measure by

Table 1

NC ðn ¼ 25Þ SZ LOW TDI ðn ¼ 22Þ SZ HIGH TDI ðn ¼ 25Þ

# Female/Male 18/7 11/11 10/15

Age (years) 30.5 (11.8)a 34.9 (8.3) 34.1 (9.9)

Education (years) 15.5 (2.6) 14.3 (3.1) 14.4 (2.0)

Estimated verbal IQ 105.8 (8.5) 105.9 (12.1) 102.0 (9.8)

BPRS NA 40.8 (13.0) 43.3 (13.6)

GASb 78.3 (8.4) 40.8 (13.0) 40.7 (10.3)

Medication amount

(CPZ equivalent units) NA 509.4 (299.8) 578.8 (327.3)

TDI Total scorec 4.2 (6.2) 4.9 (3.8) 29.0 (17.4)

aMean (SD).bNC vs. SZ Low TDI, F ð1; 44Þ ¼ 136:0, po.001; NC vs. SZ High TDI, F ð1; 44Þ ¼ 194:7, po.001.cNC vs. SZ High TDI, F ð1; 44Þ ¼ 38:4, po.001; SZ Low TDI vs. SZ High TDI, F ð1; 45Þ ¼ 40:3, po.001.


the Global Assessment Scale (GAS) (Endicott, Spitzer, Fliess, & Cohen, 1976) than NC,but did not differ from each other. The two patient groups did not differ from each other insymptom severity as assessed using the Brief Psychiatric Rating Scale (BPRS) (Overall &Gorham, 1962), or in daily dose of medication (chlorpromazine, CPZ, equivalent units).The two patient groups differed significantly from each other only in average total TDIscores.

1.2. Materials and procedure

Stimuli consisted of 24 sets of noun–noun conceptual combinations taken from Estesand Glucksberg (2000). Three different types of noun–noun pairs were counterbalancedacross the 24 items. In the first type of combination the modifier noun had a semanticfeature that was highly salient, and the head noun had a semantic dimension that washighly relevant for that feature (HH; e.g., zebra bag). The HH pairs were thus designed toprovide a high degree of contextual constraint for a property interpretation. The two othertypes of pairs were designed to impose a contextual constraint favoring a relationalinterpretation over a property interpretation. In the second type of combination, themodifier noun had a semantic feature that was highly salient but the head noun did nothave a semantic dimension that was highly relevant for that feature (HL; e.g., zebra trap).In the third type of combination, the modifier noun did not have a semantic feature thatwas highly salient, but used the head noun from the HH pair that had a relevant dimensionin the context of the HH pair (LH; e.g., donkey bag).Three rating forms were created in order to counterbalance each item across the

three conditions of the experiment (i.e., HH, HL, LH). Only one rating form was givento each participant. Thus, no list contained the same pair more than once, and pairsof each type were included in approximately equal numbers on each list. Participantswere instructed to write their interpretation of each pair on the line provided belowthe pair. They were also instructed to rate (on a scale of 1–5) how difficult it was tocreate that interpretation. The task was not timed, and it took approximately 15min tocomplete.A scoring system was devised to classify participants’ responses into three broad

response categories: property interpretation, relational interpretation, and ‘‘other’’ (i.e.,neither property nor relational) interpretations. We based the coding scheme on that usedby Estes and Glucksberg (2000), but elaborated upon it as well. For example, Estes andGlucksberg reported only results for property interpretations. We report results forproperty interpretations, relational interpretations, and non-classifiable (i.e., ‘‘other’’)interpretations. Estes and Glucksberg also restricted their classification of propertyinterpretations to only those responses that exactly matched what the combination wasmeant to bias, whereas we scored property interpretations using a more liberal criterion(i.e., any property interpretation generated). Examples of each interpretation type andadditional subdivisions of each category are presented in Table 2. The completed ratingforms were scored by four of the authors who obtained extensive training in this codingscheme and were blind to participant group status at the time of scoring (DT, ML, MN,LR). The coded responses were transformed into percentage of responses in each majorinterpretation category (i.e., property, relational, other) for each combination type (i.e.,HH, HL, LH). The difficulty ratings were averaged for each participant as a function ofeach combination type and interpretation category.

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Table 2

Response category Response sub-category Explanation Example

Property interpretation Property as defined by

Estes and Glucksberg

(2000)

Demonstrates a salient

feature and relevant

dimension

Zebra bag—a bag with

black and white stripes

Property/non-salient Demonstrates a

property interpretation,

but not involving the

relevant dimension

Octopus tray—a tray

shaped like an octopus

(salient property is # of

legs)

Property/non-salient/

relevant dimension

Demonstrates a

property interpretation

for the relevant

dimension, but not for

the salient feature

Turtle jumper—a person

who is quick to finish a

task (salient feature is

slowness: the dimension

of speed was used but

not the salient feature)

Property/salient/non-

relevant dimension

Demonstrates a

property interpretation:

mentions salient feature

but places it in a non-

relevant dimension

Octopus table—a table

with eight place settings

(relevant dimension was

legs of the table)

Property/switched head Property attribution

from the head to the

modifier

Blimp eagle—a blimp in

the shape of an eagle

Relation interpretation Relation as defined by

Estes and Glucksberg

(2000)

Relation is created

between the head and

modifier: usually no

mention of salient

feature or relevant

dimension

Skunk scraps—pieces of

dead skunk

‘‘Other’’ interpretation Ambiguous word

interpretation

One of the words is

given an unintended

meaning by using a

homonym of the

intended word

Frog pen—an enclosure

in which to keep frogs

(where intended

meaning of pen

pertained to writing

implement)

Vague The logic is not

apparent, or there is not

enough information to

determine a

classification

Cotton luggage—

luggage that is only the

essentials

Vague/associated The response is vague,

but some logic is

apparent

Turtle jumper—a hard

job

Vague/no information The only words used are

the head and the

modifier

Cherry grease—grease

of a cherry

D. Titone et al. / Journal of Neurolinguistics 20 (2007) 92–110 99

1.3. Results

Property interpretations: Fig. 1 presents the percentage of property interpretations acrossthe three participant groups. We computed a 3 (pair type: HH, HL, LH) � 3 (group:

ARTICLE IN PRESS

0

10

20

30

40

50

60

70

80

Controls (n = 25) SZ Low TDI (n = 22) SZ High TDI (n = 25)

Per

cent

age

of P

rope

rty

Inte

rpre

tatio

ns

HH HL LH

Fig. 1. Percentage of property interpretations (plus or minus 1 standard error of the mean) for controls, SZ Low

TDI, and SZ High TDI, as a function of pair type.

D. Titone et al. / Journal of Neurolinguistics 20 (2007) 92–110100

Controls, SZ Low TDI, SZ High TDI) mixed-design ANOVA, with pair type as a within-subjects factor and group as a between-subjects factor. The only significant effect was amain effect of pair type (F ð2; 138Þ ¼ 169:4, po.0001). Across the three groups, thepercentage of property interpretations was significantly higher for HH pairs (mean ¼ 66:5;SD ¼ 24) than for HL pairs (mean ¼ 25:3; SD ¼ 19) and LH pairs (mean ¼ 19:5;SD ¼ 16) (HH vs. HL, F ð1; 138Þ ¼ 219:7, po.0001; HH vs. LH, F ð1; 138Þ ¼ 284:4,po.0001)). The percentage of property interpretations was also significantly higher for HLpairs than for LH pairs (HL vs. LH, F ð1; 138Þ ¼ 4:2, po.05), although the magnitude ofthis effect is much smaller than the difference between HH pairs and HL or LH.The absence of a main effect of group indicated that both subgroups of SZ and the

controls were more likely to produce property interpretations for noun–noun combina-tions that were biased to elicit property interpretations (e.g., HH combinations) thannoun–noun combinations that were biased against property interpretations (e.g., HL andLH). The finding that HL pairs were associated with significantly more propertyinterpretations than LH pairs indicates that the presence of a highly salient feature in themodifier noun slightly but significantly favored property interpretations over relationalinterpretations. These results suggest that the capacity to create property-basedinterpretations for novel noun–noun combinations is intact in SZ and does not vary asa function of the amount of independently rated thought disorder. Note that the overallpattern of results is the same when the more restrictive definition of propertyinterpretations used by Estes and Glucksberg (2000) is applied to the data.

Relational interpretations: Fig. 2 presents the percentage of relational interpretationsacross the three participant groups. We computed a 3 (pair type: HH, HL, LH) � 3(group: Controls, SZ Low TDI, SZ High TDI) mixed-design ANOVA, with pair type as awithin-subjects factor and group as a between-subjects factor. The results yielded a maineffect of group (F ð2; 69Þ ¼ 5:1, po.01), a main effect of pair type (F ð2; 138Þ ¼ 103:3,po.0001), and a group � pair-type interaction (F ð4; 138Þ ¼ 2:5, po.05). Inspection ofFig. 2 shows that this interaction was driven by significantly fewer relational responses for

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0

10

20

30

40

50

60

70

80


Per

cent

age

of O

ther

Inte

rpre

tatio

ns

HH HL LH

Fig. 3. Percentage of ‘‘other’’ interpretations (plus or minus 1 standard error of the mean) for controls, SZ Low


0

10

20

30

40

50

60

70

80


Per

cent

age

of R

elat

iona

l Int

erpr

etat

ions

HH HL LH

Fig. 2. Percentage of relational interpretations (plus or minus 1 standard error of the mean) for controls, SZ Low



the HL and LH pairs in the SZ High TDI group than in the SZ Low TDI or the NCgroups, who did not differ from each other. A sub-ANOVA comparing the SZ High TDIgroup and the controls confirmed a significant group � pair-type interaction(F ð2; 96Þ ¼ 4:6, po.05): these two groups differed significantly for HL and LH pairs(po.05) but not for HH pairs. The group � pair-type interaction was not significant incomparison of SZ Low TDI participants and NC.


Although participants in all three groups were more likely to create relationalinterpretations for novel noun–noun combinations designed to elicit relational interpreta-tions (e.g., HL and LH combinations) than for noun–noun combinations designed to elicitproperty interpretations (e.g., HH combinations), the percentage of relational interpreta-tions was inversely related to amount of thought disorder in SZ. SZ High TDI patientscreated significantly fewer relational interpretations than NC, whereas SZ Low TDIpatients and NC did not differ in percentage of relational interpretations.‘‘Other’’ interpretations: Fig. 3 presents the percentage of other interpretations across the

three participant groups. We computed a 3 (pair type: HH, HL, LH) � 3 (group:Controls, SZ Low TDI, SZ High TDI) mixed-design ANOVA, with pair type as a within-subjects factor and group as a between-subjects factor. The results yielded significant maineffects of group (F ð2; 69Þ ¼ 6:5, po.01) and pair type (F ð2; 138Þ ¼ 5:7, po.01). SZ HighTDI participants created significantly more ‘‘other’’ responses (mean ¼ 26:9, SD ¼ 27)than NC (mean ¼ 10:8, SD ¼ 14) (po.05), but SZ Low TDI participants (mean ¼ 13:1,SD ¼ 19) and NC did not differ. HH combinations elicited significantly fewer ‘‘other’’responses (mean ¼ 12:3, SD ¼ 18) than the HL (mean ¼ 19:6, SD ¼ 21) or LHcombinations (mean ¼ 19:5, SD ¼ 25) (contrasts with HH combinations, respectively,F ð1; 38Þ ¼ 8:8, po.01; F ð1; 138Þ ¼ 8:2, po.01) in all groups. HL and LL combinations didnot differ in proportion of ‘‘other’’ responses.These results indicate that SZ High TDI participants were more likely than SZ Low TDI

and NC to create interpretations for novel noun–noun combinations that could not beclassified as either property or relational interpretations, and thus were only vaguely ortangentially related to a plausible interpretation of the pair. This tendency was somewhatmore pronounced for the HL and LH combinations, but the group � pair-typeinteraction was not significant. To illustrate the kinds of responses that were observed forthe three groups, Table 3 presents example property, relational, and ‘‘other’’ responsesfrom the patient groups for several combinations.

Mean difficulty ratings: SZ High TDI participants were less likely than the other groupsto create relational interpretations for noun–noun pairs designed to elicit relationalinterpretations and more likely to create ‘‘other’’ interpretations. To evaluate thepossibility that SZ High TDI found HL and LH pairs more difficult to process relationally

Table 3

Property example Relation example Other example

Zebra bag (HH) Striped purse Bag made from A fun accessory

zebra skin

Zebra trap (HL) Black and white Trap to catch Referee with a gun

cage zebras

Donkey bag (LH) Bag shaped Saddlebag for a Saddle for a donkey

like a donkey donkey

Mouse car (HH) Very small car A car that mice A car trapped by

drive something

Mouse truck (HL) Small truck Truck that Used at Disneyworld

carries mice to empty trash

Cat car (LH) Car that looks Toy car for Automobile of fancy

like a cat cats women

ARTICLE IN PRESS

1

1.5

2

2.5

3

HH HL LH

Ave

rage

Diff

icul

ty R

atin

gs (

1 =

low

; 5 =

hig

h)

1

1.5

2

2.5

3

HH HL LH

Ave

rage

Diff

icul

ty R

atin

gs (

1 =

low

; 5 =

hig

h)

1

1.5

2

2.5

3

HH HL LH

Ave

rage

Diff

icul

ty R

atin

gs (

1 =

low

; 5 =

hig

h)

(b)

(a)

(c)

Property Interpretation Relational Interpretation



Fig. 4. (a) Average difficulty ratings (1 ¼ low; 5 ¼ high) for property and relational interpretations (plus or minus

1 standard error of the mean) as a function of pair type for controls. (b) Average difficulty ratings (1 ¼ low;

5 ¼ high) for property and relational interpretations as a function of pair type for SZ Low TDI. (c) Average

difficulty ratings (1 ¼ low; 5 ¼ high) for property and relational interpretations as a function of pair type for SZ

High TDI.



than the other groups, we analyzed the subjective ratings for each pair on the difficultyassociated with creating each kind of interpretation.Figs. 4a–c present the mean difficulty ratings for Controls, SZ Low TDI, and SZ High

TDI participants, respectively, as a function of pair type and interpretation category. Wecomputed a 3 (pair type: HH, HL, LH) � 3 (group: Controls, SZ Low TDI, SZ HighTDI) � 2 (interpretation category: property, relation) mixed-design ANOVA, with pairtype and interpretation categories as within-subjects factors and group as a between-subjects factor. The mean ratings for ‘‘other’’ interpretations were not included in thisanalysis because of the relatively infrequency of these responses across the groups.The results revealed a significant pair type � interpretation category interaction

(F ð2; 138Þ ¼ 8:2, po.001), and a significant three-way pair type � interpretation category� group interaction (F ð4; 138Þ ¼ 3:5, p o.01). We computed sub-ANOVAs for eachsubject group to explore the nature of these significant interactions. Among NC, there weremain effects of pair type (F ð2; 38Þ ¼ 4:1, po.05) and interpretation category(F ð1; 24Þ ¼ 8:1, po.01), and the pair type � interpretation category interaction justmissed statistical significance (F ð2; 48Þ ¼ 2:9, p ¼ :07). As shown in Fig. 4a, these effectsreflect the finding that property interpretations for HL pairs were rated as more difficultthan the other pair types and interpretation categories (po.05). Thus, although theaverage difficulty ratings were quite low overall (i.e., between 2 and 2.5 on a 5 point scale),controls found it more difficult to interpret combinations when the modifier noun for acombination that had a salient feature mapped to a head noun that did not have a relevantdimension for that feature than when a relevant dimension was present as in the HH pair.Among SZ Low TDI patients there were no significant effects. Difficulty ratings were

also low overall (i.e., averaging approximately 2 on a 5 point scale) (see Fig. 4b), and didnot discriminate between pair types and interpretation categories. Among SZ High TDIparticipants the sub-ANOVA yielded a significant pair type � interpretation categoryinteraction (F ð2; 48Þ ¼ 13:5, po.001). Subjective perceptions of response difficulty co-varied with the dominant response tendency in each category (Fig. 4c). Thus, difficultyratings for HH combinations designed to elicit property interpretations were significantlyhigher when property interpretations were created than when relational interpretationswere created for the same pairs (po.05). In contrast, difficulty ratings for HLcombinations and LH combinations designed to elicit relational interpretations weresignificantly higher when relational interpretations were created than when propertyinterpretations were created for the same pairs.Importantly, difficulty ratings for SZ High TDI participants were as low overall as those

of the other groups (i.e., averaging approximately 2–2.5 on a 5 point scale). Thus, these datasuggest that the significant reduction in relational responses for SZ High TDI participantsdid not arise because the patients found the specific word combinations to be more difficultsubjectively. In support of this interpretation, when the original omnibus ANOVA wascomputed only for SZ High TDI and Control participants, there was a significant maineffect of interpretation category (F ð1; 46Þ ¼ 6:2, po.05) and pair type � interpretationcategory interaction (F ð2; 96Þ ¼ 10:8, po.001), but no significant main effect of group.

2. General discussion

This study employed a conceptual combination task to address the question of whethersemantic processing abnormalities in SZ arise from deficits in semantic storage or access,


or the controlled use of semantic memory representations. The results of this study suggestthat the integrity and initial access of semantic memory is spared in SZ, whereas the abilityto engage in the controlled processing operations necessary to make flexible use ofsemantic material, once retrieved, is impaired. Neither high nor low TDI patients differedfrom controls in how they interpreted noun–noun combinations designed to elicit propertyinterpretations. However, high TDI SZ patients produced significantly fewer relationalinterpretations for combinations designed to elicit relational interpretations andsignificantly more ‘‘other’’ unclassifiable interpretations than low TDI patients andcontrols. Differences in subjective difficulty across the different pairs or interpretationtypes did not account for the selective deficit involving relational interpretations.Moreover, the specificity of this deficit in high TDI SZ was unrelated to severity ofillness, global level of functioning, or dose of medication.

The findings from the present study are consistent with our previous work in suggestingthat semantic processing impairments in SZ arise when the flexible and contextuallyappropriate use of semantic memory representations is required to resolve ambiguousinput (Titone et al., 2000, 2002; Titone & Levy, 2004). Titone et al. (2000), for example,found that SZ patients and controls showed semantic priming for the less frequentmeaning of lexically ambiguous words when the sentence context moderately or stronglybiased the less frequent meaning (e.g., the dance meaning of ball for the sentence, ‘‘Because

it lasted all night, she really liked the ball’’). However, unlike controls, SZ patients showedcontinued priming of the contextually irrelevant dominant meaning of lexically ambiguouswords when the sentence context moderately biased the less frequent subordinateinterpretation. For example, SZ patients showed significant priming of the toy meaning ofball for the sentence, ‘‘Because it lasted all night, she really liked the ball’’, suggesting thatthe patients failed to inhibit the contextually irrelevant meaning. These findings suggestedthat SZ patients made use of sentence contexts to activate intact semantic memoryrepresentations, but were impaired in flexibly modulating activation of semantic memoryas a function of context. A study that examined processing at a lexical rather than semanticlevel reported a similar pattern of results (Titone & Levy, 2004). SZ patients were impairedin identifying spoken English words that sounded similar to many other high-frequencywords, but intact in identifying words that had relatively few lexical competitors.

We obtained a similar pattern of results in a study that examined the comprehension ofnon-literal idiomatic sequences in SZ (Titone et al., 2002). The study of non-literal, orfigurative, language processing has a long history in SZ, in that a number of clinical tests of‘‘thought disorder’’ involve the interpretation of familiar proverbs (e.g., a rolling stone

gathers no moss). Non-literal idiomatic sequences do not comprise a homogeneous class ofexpressions; however, they vary along a number of linguistic dimensions that may affecthow idioms are normally processed (Titone & Connine, 1994a,b 1999). For example, someidioms are literally plausible such as ‘‘skate on thin ice’’, whereas other idioms are literallyimplausible, such as ‘‘pay through the nose’’. Using a cross modal priming paradigm,Titone et al. (2002) found that SZ patients showed reduced semantic priming for literallyplausible idiomatic expressions (e.g., ‘‘skate on thin ice’’), but intact semantic priming forliterally implausible idiomatic expressions (e.g., ‘‘pay through the nose’’). Thus, the storageof non-literal sequences was not impaired, but SZ patients had difficulty settling on a singleinterpretation after semantic representations were retrieved into working memory. Theresults of this series of studies are consistent with meta-analyses showing that post-lexicalor strategic aspects of semantic processing are impaired, whereas semantic storage and


automatic semantic processing seem to be spared, in SZ (Barrera et al., 2005; Kerns &Berenbaum, 2002, 2003; Leeson et al., 2005; Minzenberg, Ober, & Vinogradov, 2002).The key variable linked to the reduction in relational interpretations in the present study

was quantity of thought disorder. Interestingly, impaired lexical processing was alsosignificantly correlated with increased thought disorder as assessed with the TDI (Titone &Levy, 2004). We did not examine whether impairments in idiomatic processing and lexicalambiguity resolution are more severe for SZ High TDI participants (Titone et al. 2000,2002). It is intriguing to consider why impairments in relational interpretations would beassociated with increased amounts of thought disorder in SZ. Combinatory thinking, onecharacteristic of schizophrenic thought disorder, involves creating relationships betweenunrelated percepts. It seems reasonable to presume that the predisposition to makerelational interpretations that are inappropriate interferes with the ability to makerelational interpretations that are not only appropriate, but are called for by the context ofa particular noun–noun combination. Thus, a core deficit in the ability to inhibitcontextually irrelevant semantic representations may lead to the selection of less coherentrelational interpretations. This interference effect is particularly pronounced in contextsthat are semantically less constrained (i.e., relational) compared with contexts that aresemantically more constrained (i.e., property).These results bear on studies of conceptual combination in other populations that have

semantic processing deficits. In a recent study examining conceptual combination inindividuals with Alzheimer’s disease (AD), the pattern of deficits was the opposite of thatfound in SZ patients in the present study (Taler, Chertkow, & Saumier, 2005). Taler et al.asked three groups of AD patients, age-matched controls, and young adults to select whichof three interpretations best matched noun–noun combinations, although the compoundswere undifferentiated with respect to the HH, HL, and LH dimensions. The possiblechoices on each trial consisted of a property interpretation (termed integrationinterpretations), or a relational interpretation (termed association interpretations). ADpatients and older adult controls made relational interpretations with equivalentfrequency, but AD patients were less likely to make property interpretations and morelikely to choose the semantic foils than older adult controls. Although the stimuli andprocedures are not entirely comparable to those used in the present study, we found thatSZ High TDI were impaired in making relational interpretations and intact in makingproperty interpretations.The possible double dissociation between property and relational interpretation deficits

in AD and SZ High TDI patients in these two studies suggests that multiple processes thatoperate independently may be involved in conceptual combination. Such a conclusion isconsistent with other work on conceptual combination in normals. A number of studiessupport the notion that conceptual combination is governed by at least two independentprocesses that proceed in parallel (Estes, 2003; Wisniewski, 1997; Wisniewski & Love,1998), although some models propose one cognitive mechanism for the full range ofcombination interpretations (Gagne, 2002a; Gagne & Shoben, 2002). Support for multipleprocesses in conceptual combination is also found in a recent electrophysiological study(Kounios et al., 2003), although the kinds of combinations and interpretations studied donot perfectly map onto the property and relational interpretation distinction made here.Thus, data from the present study and previous studies suggest that distinct neuralprocesses may lead to qualitatively different kinds of conceptual combination interpreta-tions. Further work is necessary to resolve this issue more fully.


It is possible that the kinds of property interpretations examined in the present studyand in the Estes and Glucksberg (2000) study have lexical rather than conceptualprocessing origins. That is, the HH combinations (e.g., zebra bag) were designed so that themodifier noun had a salient feature that could be mapped to the head noun. Therefore, theprocesses involved in generating a property attribution for these combinations are likely tobe by-products of the normal word recognition and semantic activation process (Estes,2003; Gagne, 2002b). Indeed, it is this view of property interpretations that motivated ourprediction that comprehension of combinations that were biased towards propertyinterpretations would be intact in SZ. It is also possible, however, that comprehenders maygenerate property interpretations for conceptual combinations that do not have aparticularly salient feature of the modifier noun or relevant dimension of the head noundifferently from those that do. In that case property interpretations could arise fromconceptual rather than lexical processes. Thus, property interpretations may be comprisedof two types: those that are based on lexical-semantic saliency, as in the HH combinationsused by us as well as Estes and Glucksberg (2000), and those that are conceptually based,for example, when a property interpretation is generated for HL, LH combinations, orother kinds of combinations. Thus, the double dissociation between AD and SZ High TDIpatients may solely rest on the comparison of lexically driven property interpretations andrelational interpretations. Further work is needed to clarify the range of possibleinterpretations of conceptual combinations and whether they arise from similar ordissimilar neurocognitive systems.

To conclude, the present study demonstrated that individuals with SZ with highamounts of thought disorder were impaired in generating relational interpretations ofconceptual combinations. These impairments were specific to noun–noun pairs that weredesigned to preferentially bias relational interpretations. Thus, SZ patients with highamounts of thought disorder are not globally impaired on semantic tasks, but rather showimpairments only under circumstances that required controlled and flexible use of materialretrieved from semantic memory. Notably, the predominant features of the thoughtdisorder shown by the high thought disorder subgroup of patients involved findingunrealistic relationships between unrelated things and idiosyncratic semantics. In contrast,individuals with SZ were not impaired in generating property attribution interpretationsof conceptual combinations that were designed to preferentially bias property interpreta-tions. Thus, when a semantic task required that information be retrieved from semanticmemory, individuals with SZ performed normally, suggesting that the structure and initialaccess of their semantic memory representations were intact. Further work will benecessary to clarify which components of thought disorder are responsible for theseimpairments, and to determine which neural systems that underlie these processes arecompromised in SZ.

Acknowledgments

We gratefully acknowledge support from the Canada Research Chairs program,NSERC, NARSAD, the Essel Foundation, the Canadian Foundation for Innovation,the McGill Research Development Fund, NIMH Grants MH31340 and MH49487,and the Stanley Scholar Fund. We are grateful to Dr. Philip S. Holzman and MichaelColeman for their assistance in scoring thought disorder protocols using the ThoughtDisorder Index.


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