Schizotypy and language: A review

Journal of Neurolinguistics 23 (2010) 193–203

Contents lists available at ScienceDirect

Journal of Neurolinguistics journal homepage: www.elsevier.com/locate/ jneuroling

Schizotypy and language: A review Michael Kiang* Department of Psychiatry & Behavioural Neurosciences, McMaster University, St. Joseph’s Healthcare, CMHS, 100 West 5th Street, Hamilton ON L8N 3K7, Canada

a r t i c l e i n f o

a b s t r a c t

Article history: Received 7 January 2009 Received in revised form 13 March 2009 Accepted 13 March 2009

The schizotypal personality trait of odd speech shares features with disorganized speech in schizophrenia. Meehl’s original model of schizotypy as manifestation of a genetic diathesis for schizophrenia included odd speech as a core feature, a view supported by results of subsequent family-genetic studies. Researchers have investigated the mechanisms of unusual language production in schizotypy using neuropsychological and neurophysiological methods. The results suggest that schizotypy is associated with differences in how meaningful stimuli activate related concepts in semantic memory, but the pattern of these results is mixed – with different studies reporting either increased or decreased activation of related concepts in schizotypy. However, these apparently discordant results may reflect increased activation of weakly related concepts at shorter intervals following meaningful stimuli, together with underactivation of both strongly and weakly related concepts at longer intervals. Further research is needed to clarify the neurophysiological basis of these anomalies, and the exact conditions under which each occurs; and to ascertain whether either or both mediate unusual speech. This knowledge could point to analogous mechanisms underlying schizophrenic disorganized speech. Ó 2009 Elsevier Ltd. All rights reserved.

Keywords: Personality traits Schizotypal personality Schizophrenia Language Semantic priming Cognitive processes

1. Introduction One of the diagnostic traits of schizotypal personality disorder (SPD), according to the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), is ‘‘odd speech,’’ exemplified by

* Tel.: þ1 905 522 1155x36814; fax: þ1 905 540 6533. E-mail address: [email protected] 0911-6044/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jneuroling.2009.03.002

194

M. Kiang / Journal of Neurolinguistics 23 (2010) 193–203

‘‘vague, circumstantial, metaphorical, overelaborate, or stereotyped’’ language (American Psychiatric Association, 2000). This article will briefly review the concept of schizotypy from a historical perspective, from its introduction in the 1950s through its inclusion in DSM. We will describe features of schizotypal language observed in language production studies, and will review neuropsychological and neurophysiological experiments that have aimed to identify the underlying brain mechanisms of these features. We will then summarize current hypotheses about these mechanisms. According to one such hypothesis, schizotypy is associated with greater activation by meaningful stimuli of their weak associates in semantic memory, possibly due to a relative overactivation of right- versus lefthemisphere language processing. According to a different hypothesis, unusual language in schizotypy results from decreased use of context to activate related concepts and/or to inhibit unrelated concepts, possibly due to aberrant frontal lobe function. 2. Schizotypy and SPD The usage of the term schizotypal has evolved since its introduction by Rado (1953), who proposed that clinical symptoms in schizophrenia patients are one manifestation of an underlying schizophrenic phenotype (or schizotype) of personality organization present throughout these individuals’ lifespan. According to Rado’s model, the schizotype results from an interaction between a schizophrenic genotype and environmental factors. Rado stated that the common feature of schizotypal individuals is a ‘‘fundamental and all-pervasive’’ deficiency in the capacity to experience pleasure. However, it is only a subset of schizotypal individuals who, as a result of stress, experience a schizophrenic breakdown. Rado’s model included the schizophrenic symptom of disorganized speech, or thought disorder, among the possible features of such decompensation, but did not include atypical language as an obligatory trait of the underlying schizotypal personality. Meehl (1962; see also Lenzenweger (2006)) extended the concept of schizotypal personality (or schizotypy), proposing that a genetically determined defect in neural function1 invariably results in the development of a set of schizotypal traits. According to Meehl, one of these core traits, based on reports of its elevated prevalence in schizophrenia patients’ non-diagnosed relatives, is thought disorder, which he also described as ‘‘associative dyscontrol or, so as to include the very mildest forms it may take, cognitive slippage.’’ The other core schizotypal traits in this model were the anhedonia emphasized by Rado, interpersonal aversiveness, and ambivalence. Like Rado, Meehl believed that schizotypy was a necessary condition for schizophrenia, but that only a subset of schizotypes develop schizophrenia. In the 1960s, results of large-scale adoption studies (reviewed by Ingraham, 1995) provided further evidence for a genetic link between schizophrenia and schizotypy. Using blinded, structured psychiatric interviews, these studies found that non-affected relatives of schizophrenia patients had a higher than average prevalence of certain personality traits that were qualitatively similar to schizophrenic symptoms, but less severe. These observations led to inclusion of these traits as criteria for SPD in the third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III; American Psychiatric Association, 1980). One such trait was ‘‘odd communication,’’ paralleling schizophrenic disorganized speech; the others were inadequate rapport in face-to-face interaction, magical thinking, ideas of reference, suspiciousness, recurrent perceptual illusions, social isolation, and undue social anxiety or hypersensitivity to criticism. A diagnosis of SPD required the presence of four or more of these traits. In DSM-IV (American Psychiatric Association, 2000), the wording of some trait descriptors was revised; thus, ‘‘odd communication’’ was changed to ‘‘odd thinking and speech’’. In addition, a ninth trait, ‘‘odd behaviour’’, was added, and the presence of at least five traits was now required to diagnose SPD. Since DSM-III was published, further evidence has emerged for an increased prevalence of SPD (as diagnosed by DSM-based semi-structured interviews) in relatives of schizophrenia patients (Asarnow et al., 2001; Baron et al., 1985; Kendler, Gruenberg, & Kinney, 1994; Kety, 1983). Taken together, these results suggest that SPD has a prevalence of 10–15% in first-degree relatives of schizophrenia patients

1

Meehl referred to this putative neural functional defect as schizotaxia.

M. Kiang / Journal of Neurolinguistics 23 (2010) 193–203

195

(Cadenhead & Braff, 2002), compared to 1% in the general population (Torgersen, Kringlen, & Cramer, 2001). Odd speech, in particular, was found by Kendler, McGuire, Gruenberg, and Walsh (1995) to be the schizotypal trait most strongly discriminating non-schizophrenic relatives of schizophrenia patients from control individuals. In contrast to the structured diagnostic interviews for schizotypy used by the above studies, selfreport questionnaire assessments of schizotypal characteristics, although easier to administer, have generally exhibited less sensitivity for discriminating relatives of schizophrenia patients from controls. Some studies which did not find a difference between these groups on self-rating scales may have been limited by the use of instruments that were not specifically designed to measure DSM schizotypy (Catts, Fox, Ward, & McConaghy, 2000; Jones et al., 2000; Kendler, Thacker, & Walsh, 1996). Such instruments include the Magical Ideation (Eckblad & Chapman, 1983), Perceptual Aberration (Chapman, Chapman, & Raulin, 1978), Physical Anhedonia (Chapman, Chapman, & Raulin, 1976) and Social Anhedonia scales (Chapman et al., 1976), which were developed prior to DSM-III, to assess personality traits hypothesized to predispose to schizophrenia; these traits correlate with and qualitatively overlap, but are not necessarily identical to, the DSM schizotypal traits (Chapman, Chapman, & Kwapil, 1995). A more recent self-report scale, designed specifically to assess each of the DSM-III schizotypal traits, is the Schizotypal Personality Questionnaire (SPQ; Raine, 1991). A number of studies have reported higher schizotypy, as measured by the SPQ, in first-degree relatives of schizophrenia patients, than in control individuals (Calkins, Curtis, Grove, & Iacono, 2004; Chang & Lenzenweger, 2005; Kremen, Faraone, Toomey, Seidman, & Tsuang, 1998; Vollema, Sitskoorn, Appels, & Kahn, 2002; Yaralian et al., 2000), although at least one other study did not find significant differences between the two groups (Compton, Chien, & Bollini, 2007). Conversely, some (but not all) studies have found an elevated prevalence of schizophrenia (up to 5%, versus a population prevalence of about 1%) in relatives of individuals with interview-diagnosed SPD (Cadenhead & Braff, 2002; Tsuang, Stone, Tarbox, & Faraone, 2002). On the other hand, however, there is a lack of evidence that schizotypy in the general population as measured by self-report questionnaires is correlated with increased familial prevalence of schizophrenia. This lack of evidence may stem from inadequate sensitivity of self-report instruments; the likelihood that schizotypal traits in some individuals may arise from causes other than the genetic liability to schizophrenia; relatively small effect sizes of any increased risk; and/or the practical difficulty of ascertaining whether relatives of individuals sampled from the general population have schizophrenia. Consistent with the above evidence for a common genetic diathesis for SPD and schizophrenia, persons with SPD share a number of neuroanatomical and neurophysiological findings with schizophrenia patients (reviewed by Siever & Davis, 2004) – including smaller temporal lobe volumes, reduced frontotemporal connectivity (Nakamura et al., 2005), and reduced coordination of eye movements, albeit generally to a lesser degree. Thus, studying the neurophysiological mechanisms of these findings in SPD may help to shed light on analogous pathophysiological processes in schizophrenia. This approach has the advantage that, in individuals with SPD, these mechanisms can be studied free of the confounding effects of factors such as psychotropic medication, reduced educational attainment, and institutionalization, which often are present in patients with schizophrenia. 3. Characteristics of unusual language production in schizotypy Neuropsychological tests have afforded researchers more detailed insight into the specific characteristics of unusual language production in schizotypy. In one type of assessment, participants produce free responses to standardized questions. These responses are transcribed and then rated on different aspects of atypicality. An advantage of this method is its ability to elicit naturalistic language, and to assess for a wide variety of anomalies. A potential disadvantage is the difficulty of ensuring rater consistency across studies. A detailed assessment of this type is the Thought Disorder Index (TDI; Solovay et al., 1986). In the TDI, participants’ responses on the Rorschach inkblot test or the Wechsler Adult Intelligence Scale (WAIS) verbal subscale are scored for instances of 23 categories of unusual language, such as vagueness, peculiar expressions, looseness of associations, autistic (faulty) logic, and absurd (irrelevant) responses to questions. A few studies have examined TDI results as a function of schizotypy. In one study, non-clinical participants with high (more than 2 standard deviations above

196

M. Kiang / Journal of Neurolinguistics 23 (2010) 193–203

the mean) versus low (lower than 0.5 standard deviations below the mean) scores on the schizotypal trait of perceptual illusions (measured by the Perceptual Aberration Scale) produced more frequent idiosyncratic words expressions on the TDI, even though the two groups were matched on verbal intelligence (Coleman, Levy, Lenzenweger, & Holzman, 1996). In addition, Edell (1987) found that individuals with SPD had higher total TDI scores than control individuals matched on verbal IQ. In another study, schizophrenia patients’ relatives with SPD scored higher than control individuals on a factor of TDI items that included autistic logic and absurd responses (Vaever et al., 2005). A limitation of the latter study was that it did not ascertain whether the groups differed on general intelligence, as such a difference could conceivably have contributed to the results. Taken together, these results suggest that higher schizotypy is associated with speech containing idiosyncratic word usage and illogical associations. Some aspects of participants’ responses to standard questions can be quantified in relation to existing language-production norms, thus obviating reliance on rater judgments. Lenzenweger, Miller, Maher, and Manschreck (2007) used such a method to compare responses of high-schizotypy individuals (high scorers on both the Perceptual Aberration Scale and the Magical Ideation Scale) to those of control individuals, in a task in which participants described a painting. For each word in the responses, the authors calculated the number of normative semantic associations to it in the subsequent 100 words. Normative semantic associations include those words produced most frequently by individuals in free word-association tests, in which participants are presented with a word and asked to generate the first other word that comes to mind. These data can be ascertained from published population word-association norms (e.g., Nelson, McEvoy, & Schreiber, 1999; Palermo & Jenkins, 1970). Lenzenweger et al. (2007) found that the high-schizotypy group exhibited a higher frequency of normative word associations than did the control group. How we can reconcile this finding that higher-schizotypy individuals generated a greater frequency of normative associations with observations that schizotypal speech is idiosyncratic or unusual? Although Lenzenweger et al. (2007) did not assess whether the two groups differed in logicality or relevance of responses, a higher frequency of normative associations in the high-schizotypy group could reflect an intrusion of common associations that are irrelevant to the task at hand, potentially resulting in illogical responses. This phenomenon can be seen in the following examples of ‘‘queer’’ and ‘‘loose’’ responses, respectively, from the TDI manual (Solovay et al., 1986): [Question from WAIS] How are a fly and a tree alike? [Response] A fly has branches like a tree. [Question from the Rorschach test] What made it look like a crab? [Response] Cuz I’m Cancer the Crab maybe. My sign is cancer. My horoscope. And I’m thinking a lot about cancer too. God forbid if anybody is dying of cancer. These responses are idiosyncratic and illogical even though ‘‘tree’’ and ‘‘branch’’ are common associates in word-association norms, as are ‘‘Cancer’’ and ‘‘crab’’, and ‘‘death’’ and ‘‘cancer’’ (Nelson et al., 1999). Free word-association tests have also been used to assess response typicality as a function of schizotypy. Although such tests are less naturalistic than the language production tasks described above, they allow the systematic quantification of response typicality to specific stimuli, in relation to population norms. In one study employing a word-association test, individuals with high combined Perceptual Aberration Scale and Magical Ideation Scale scores generated more unusual responses, and fewer common responses, than did controls (Miller & Chapman, 1983). Scores on the Eysenck Psychoticism Scale were also correlated with the proportion of unusual word-association responses, at least in men (Ward, McConaghy, & Catts,1991), or with the proportion of unique responses (Merten,1993). These results parallel findings that schizophrenia patients produce less typical responses compared to controls on word-association tests (Janowsky, Huey, Storms, & Judd, 1977; Johnson & Shean, 1993; Shakow, 1980). A similar paradigm, in which multiple responses are generated, is the Category Fluency Test (CFT; Spreen & Strauss, 1998), in which individuals produce as many members of a stimulus category as possible in a given time interval. Higher SPQ scores correlated with less typical CFT responses for the fruit category (Kiang & Kutas, 2006). Overall, these results suggest that the difference in relative strength between normatively more and less typical semantic associations is reduced in individuals with higher schizotypy – leading to greater probability of producing less typical associates in word-association tests.

M. Kiang / Journal of Neurolinguistics 23 (2010) 193–203

197

Consistent with this view, persons with above-average Magical Ideation Scale scores rated both unrelated and remotely related word pairs as being more highly related than did persons with below-average scores (Mohr, Graves, Gianotti, Pizzagalli, & Brugger, 2001). The apparent discrepancy between higher-schizotypy individuals’ less typical word-association responses and their more frequent normative associations in the response to a standard question (Lenzenweger et al., 2007) could be attributable to task differences. In the Lenzenweger et al. study, participants described a painting, and thus would be expected to activate associations relevant to the task (i.e., related to the content of the painting). However, if high-schizotypy individuals are less effective than controls at activating such context-specific associations, then they may have produced instead a greater number of generically normative associations between individual words in their responses (similar to the sample TDI responses discussed above). This could be the case even though, in word-association tasks, where the cue word comprises the sole context, high-schizotypy individuals give less typical responses than do low-schizotypy individuals. 4. Schizotypy and semantic priming Overall, these reports of unusual associations in schizotypal language suggest underlying differences in how meaningful concepts activate one another in long-term semantic memory. Semantic memory is defined as our knowledge about concepts and the relationships among them. In one general model of semantic memory, concepts are nodes in a neural network, and meaningful relationships between concepts are links among these nodes (Anderson & Pirolli, 1984; Collins & Loftus, 1975; Spitzer, 1997). Related concepts include: objects and their features (e.g., CAT–FUR) or actions (CAT– MEOW); categories and their exemplars (ANIMAL–CAT); and common associates (CAT–MOUSE). A pair of concepts may be only remotely or ‘‘indirectly’’ related via one or more mediating nodes (CAT– CHEESE, mediated by MOUSE). When a concept node is activated – e.g., by its corresponding word or object stimulus – this activation then spreads through the network to other nodes, falling off as a function of decreasing relatedness. Greater activation of a concept corresponds to greater priming, or facilitation of its processing. This spreading-activation model accounts for evidence that meaningful stimuli are processed more easily when preceded by a related as compared to an unrelated context. For example, in a lexical-decision task, requiring classification of letter strings as words or nonwords, individuals are faster to recognize target words preceded by a related as compared to an unrelated prime word (Neely, 1977). This reaction-time (RT) priming effect is presumed to reflect greater activation of target concepts in semantic memory by related primes than by unrelated primes. The results of the word-association studies described previously suggest that, following a meaningful prime stimulus, the subsequent activation difference between concepts that are more versus less related to the prime is attenuated in individuals with higher schizotypy. According to one hypothesis, this attenuation could be due to an increase in the degree to which a given stimulus concept activates its relatively weaker or more remote associates in the semantic network (Mohr et al., 2001; Pizzagalli, Lehmann, & Brugger, 2001). This phenomenon could lead to the production of loose associations in speech. Some researchers have further hypothesized that this anomaly primarily affects ‘‘automatic’’ activation which normally spreads without conscious control through the semantic network within a relatively short time interval (< approximately 350 ms) after stimulus-onset – in contrast to ‘‘controlled’’ activation of related concepts, which is thought to be slower-acting, and subject to modulation by conscious, task-relevant strategies (Neely, 1977; Niznikiewicz et al., 2002). 2 Some results from experiments employing RT semantic priming paradigms are consistent with an association between schizotypy and increased spread of automatic activation to weak associates. Pizzagalli et al. (2001) examined lexical-decision RT priming effects for directly and indirectly related prime-target word pairs – representing strongly and weakly associated concepts, respectively – in high

2 However, the correspondence of early and late semantic processing with automatic and controlled responses, respectively, is not clear-cut, as there is evidence that conscious, top-down processes can modulate early activation (Barch et al., 1996; Hill, Ott, & Weisbrod, 2005), and conversely that unconscious processing can affect later activation (Deacon, Uhm, Ritter, Hewitt, & Dynowska, 1999).

198

M. Kiang / Journal of Neurolinguistics 23 (2010) 193–203

(top quartile) versus low (bottom quartile) MIS scorers. Aiming to test automatic spreading-activation following primes, they used a short prime-target onset-to-onset interval (or stimulus-onset asynchrony; SOA) of 200 ms. Overall, RTs did not differ between high and low scorers – consistent with other studies that found no differences in general lexical-decision RT as a function of schizotypal traits (Kerns & Berenbaum, 2000; Moritz et al., 1999). However, priming effects for indirectly related versus unrelated pairs (indirect priming effects) were larger in high scorers than low scorers, for left- but not right-lateralized targets. The groups did not differ in priming effects between directly related and unrelated pairs (direct priming effects). In another study, individuals with high combined PAS/MIS scores exhibited greater RT priming than did controls for target words that were semantically related to prime words but had not been produced by participants as associates of the primes in word-association norms, and hence were weak associates (Kerns & Berenbaum, 2000).3 Overall, the results of this pair of studies appear consistent with increased activation of weakly related concepts in schizotypy at the short SOAs, which have been proposed to reflect automatic activation. Other results, however, seem to indicate that schizotypy is characterized by increased activation of strong associates instead of or in addition to weak associates. Thus, Moritz et al. (1999) reported larger direct (at SOA ¼ 200 ms) as well as indirect lexical-decision RT priming effects (at SOAs of 200 and 700 ms) in healthy individuals scoring higher on a self-report measure of disorganized speech (but see Morgan, Bedford, and Rossell (2006) for a negative result with regard to direct priming effects). Another study whose results fit with increased activation of strong associates used the N400 component of the scalp-recorded event-related brain potential (ERP) to examine semantic priming. The N400 is a negativity peaking approximately 400 ms after presentation of any potentially meaningful stimulus, such as a word or picture. Its amplitude is reduced (made less negative) by factors facilitating an item’s processing (reviewed by Kutas & Federmeier, 2000) – including greater relatedness to a preceding item (Holcomb & Neville, 1991; Kutas, 1985; Kutas & Hillyard, 1980; Stelmack & Miles, 1990). With all else held constant, N400 amplitude thus indexes the degree to which concepts activate or prime one another in semantic memory: the greater the activation, the smaller the N400 negativity. Niznikiewicz et al. (2002) found that, at an SOA of 450 ms, women with schizotypal personality disorder (SPD) and control women had similar N400 amplitudes to unrelated word-pair targets, but SPD women had less negative N400 amplitudes than control women to directly related targets, suggestive of greater than normal activation of these presumably strong associates. The groups did not differ in N400 amplitudes for either class of stimuli at a longer SOA of 1000 ms. However, because it is unclear whether word-pair stimuli in this study were based on word-association norms, it is possible that the pairs, although directly related, may have been only relatively weak associates on average; if so, then the results could in fact be consistent with increased activation of weak associates in schizotypy. According to a different hypothesis, unusual speech in schizotypy results from decreased use of context to activate related concepts and/or to inhibit unrelated concepts (Kiang & Kutas, 2005; Niznikiewicz et al., 2002, 1999). The resulting underactivation of related concepts (and/or overactivation of unrelated concepts) could permit intrusion of irrelevant associations into speech. In line with this hypothesis, there is evidence that SPD is associated with larger (more negative) than normal N400 amplitudes to congruent but not incongruent sentence endings (Niznikiewicz et al., 2004, 1999) – consistent with decreased use of sentential context to pre-activate potential related completions. Likewise, higher scores on the Structured Interview for Schizotypy (Kendler, Lieberman, & Walsh, 1989) were correlated with a less than normal difference between N400 amplitudes to congruent and incongruent sentence-final words (Kimble et al., 2000). In addition, Kiang and Kutas (2005) found that SPQ scores correlated with more negative N400 amplitudes to target words representing high- and low-typicality exemplars of a category prime (corresponding to strong and weak associates, respectively), and less negative N400 amplitudes to non-exemplars (at SOAs of 2400–2800 ms) – consistent with decreased use of context to activate both strongly and weakly related items, and to inhibit unrelated items. Notably, these studies all employed relatively long SOAs

3 In this study, the prime was presented until the participant named it (up to a maximum duration of 1500 ms), and was then followed by a 350-ms interval until target onset; thus SOAs potentially ranged from 350 to 1850 ms.

M. Kiang / Journal of Neurolinguistics 23 (2010) 193–203

199

including sentence contexts; thus, their results accord with a view in which schizotypy is associated with decreased use of context to modulate ‘‘controlled’’ activation. At first glance, these findings from RT and N400 semantic priming studies seem mixed, with different results pointing to associations of schizotypy with both increased and decreased activation of related concepts following meaningful stimuli. However, the results are broadly consistent with increased activation of weakly related concepts at shorter SOAs, together with decreased activation of all related concepts at longer SOAs (including sentence contexts which build up over several seconds). Such a pattern of results would support an account in which schizotypy is associated with greater spread of (possibly automatic) activation in the semantic network at relatively short intervals after a meaningful stimulus, along with decreased use of this context to guide activation of related concepts at longer intervals (Moritz et al., 1999; Niznikiewicz et al., 2002). This account would parallel a model that has been proposed to explain semantic priming data in schizophrenia (see McCarley et al., 1999; Minzenberg, Ober, & Vinogradov, 2002). 5. Neurophysiological hypotheses for semantic activation differences in schizotypy The results of some RT priming studies described above (Kerns & Berenbaum, 2000; Moritz et al., 1999; Pizzagalli et al., 2001) suggested an increased spread of automatic activation to weak associates in schizotypy. Pizzagalli et al. (2001) proposed that this phenomenon could be based in a reduction in the normal left-hemisphere (LH) dominance in language processing. Right-hemisphere (RH) language processing, compared to its LH counterpart, has been hypothesized to activate a broader range of semantic associations (Beeman & Chiarello, 1998; Beeman et al., 1994; Chiarello, Burgess, Richards, & Pollock, 1990; Coulson & Williams, 2005; Titone, 1998). Thus, an increase in the proportion of language processing occurring in the RH might produce an overall increased spread of semantic activation. Consistent with this conjecture, Pizzagalli et al. (2001) found a correlation of schizotypy with increased indirect priming effects only when words were presented to the left hemifield, i.e., to the RH; and not when they were presented to the right hemifield. Other evidence for the occurrence of a greater share of language processing in the RH as a function of schizotypy includes a reduction of the normal righthemifield presentation advantage for lexical-decision performance in individuals with high schizotypy (Kravetz, Faust, & Edelman, 1998; Leonhard & Brugger, 1998). Reduced left lateralization of language processing in schizotypy would also parallel functional magnetic resonance imaging (fMRI) data indicating a similar phenomenon in schizophrenia (Sommer, Ramsey, & Kahn, 2001; Weiss et al., 2004), in line with theories of generally deficient hemispheric specialization in that disorder (Mitchell & Crow, 2005). Functional neuroimaging studies could potentially be helpful in testing for further evidence that schizotypy is associated with differences in the hemispheric distribution of language processing, and, if such differences are confirmed, in ascertaining the brain regions involved. The alternative hypothesis that schizotypy is associated with decreased use of context to activate related concepts following meaningful stimuli fits with the view that higher-schizotypy individuals are generally less effective in using context to guide cognitive processing. Evidence for this view has come from experiments using other cognitive paradigms. For example, Fisher, Heller, and Miller (2007) found that a combination of SPQ-measured cognitive-perceptual schizotypy and decreased performance on neuropsychological tests of frontal lobe function predicted more accurate (fewer false-positive) responses for lures on the Deese/Roediger-McDermott (Roediger & McDermott, 1995) memory task. In this task, lures are words that were not previously presented, but are semantically related to sets of previously-presented words. Higher accuracy for lures in individuals with higher schizotypy could be due to decreased use of the contextual information thought to normally cause false-positive responses. In another study (Barch et al., 2004), persons with SPD, compared to controls matched on general intelligence, made a pattern of errors on the AX-Continuous Performance Test (Servan-Schreiber, Cohen, & Steingard, 1996) suggesting that they were not as effectively using context to guide subsequent responses. An analogous reduction in the use of semantic context to activate related concepts could account for attenuated semantic priming effects in schizotypy. Reduced context use in schizotypy has been proposed to result from deficits in maintaining context in working memory (WM; Barch et al., 2004; Kiang & Kutas, 2005; McClure, Barch, Flory, Harvey, & Siever, 2008; McClure et al., 2007; Mitropoulou et al., 2005). Indeed, SPD is associated with WM deficits in the presence of normal general

200

M. Kiang / Journal of Neurolinguistics 23 (2010) 193–203

intelligence (Mitropoulou et al., 2005; Siever & Davis, 2004). Given that the prefrontal cortex has been hypothesized to play an essential role in WM (Goldman-Rakic & Selemon, 1997), WM deficits in SPD may be caused by aberrant prefrontal function, consistent with functional neuroimaging results suggesting abnormal prefrontal activation patterns in SPD (Buchsbaum et al., 1997; Koenigsberg et al., 2005). This model – in which prefrontal dysfunction produces WM deficits and, in turn, decreased use of context in cognitive tasks – would parallel a proposed neurobiological framework for contextprocessing deficits in schizophrenia (Barch et al., 1996; MacDonald et al., 2005). 6. Summary Odd speech is one of a cluster of schizotypal personality traits found with elevated frequency in undiagnosed relatives of schizophrenia patients and thus postulated to represent genetic risk for schizophrenia. These traits are associated with semantic priming differences; however, the pattern of these observed differences has been mixed – with various data suggesting that schizotypy is associated with either increased or decreased activation of related concepts following meaningful stimuli. These apparently discordant results might be explained by increased spread of activation to weakly related concepts at relatively short time intervals after a given meaningful stimulus, followed by decreased use of this context to activate related concepts at longer time intervals. The former anomaly has been proposed to originate from decreased left lateralization of language processing, whereas the latter has been hypothesized to arise from WM deficits caused by prefrontal dysfunction. Further research is needed to more definitively characterize the neurophysiological mechanisms of these anomalies, and the conditions – such as SOA, task, and sample (general population versus SPD) – under which each of them is associated with schizotypy. Moreover, additional research is needed to determine the extent to which each of these anomalies plays a causal role in unusual speech. Given that schizotypy and schizophrenia have been shown to share a range of neurophysiological abnormalities (Siever & Davis, 2004; Tsuang, Stone, & Faraone, 2000), this knowledge could inform our understanding of pathophysiological processes underlying disorganized speech in schizophrenia. Acknowledgments I am grateful to Jelena King for thoughtful comments on a draft of this article. References American Psychiatric Association. (1980). Diagnostic and statistical manual of mental disorders (3rd ed.). Washington, DC: American Psychiatric Association. American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (DSM-IV-TR). Washington, DC: American Psychiatric Association. Anderson, J. R., & Pirolli, P. L. (1984). Spread of activation. Journal of Experimental Psychology: Learning, Memory and Cognition, 10, 791–798. Asarnow, R. F., Nuechterlein, K. H., Fogelson, D., Subotnik, K. L., Payne, D. A., Russell, A. T., et al. (2001). Schizophrenia and schizophrenia-spectrum personality disorders in the first-degree relatives of children with schizophrenia: the UCLA family study. Archives of General Psychiatry, 58, 581–588. Barch, D. M., Cohen, J. D., Servan-Schreiber, D., Steingard, S., Steinhauer, S. S., & van Kammen, D. P. (1996). Semantic priming in schizophrenia: an examination of spreading activation using word pronunciation and multiple SOAs. Journal of Abnormal Psychology, 105, 592–601. Barch, D. M., Mitropoulou, V., Harvey, P. D., New, A. S., Silverman, J. M., & Siever, L. J. (2004). Context-processing deficits in schizotypal personality disorder. Journal of Abnormal Psychology, 113, 556–568. Baron, M., Gruen, R., Rainer, J. D., Kane, J., Asnis, L., & Lord, S. (1985). A family study of schizophrenic and normal control probands: implications for the spectrum concept of schizophrenia. American Journal of Psychiatry, 142, 447–455. Beeman, M., & Chiarello, C. (1998). Complementary right- and left- hemisphere language comprehension. Current Directions in Psychological Science, 7, 2–8. Beeman, M., Friedman, R. B., Grafman, J., Perez, E., Diamond, S., & Lindsay, M. B. (1994). Summation priming and coarse semantic coding in the right hemisphere. Journal of Cognitive Neuroscience, 6, 26–45. Buchsbaum, M. S., Trestman, R. L., Hazlett, E., Siegel, B. V., Jr., Schaefer, C. H., Luu-Hsia, C., et al. (1997). Regional cerebral blood flow during the Wisconsin Card Sort Test in schizotypal personality disorder. Schizophrenia Research, 27, 21–28. Cadenhead, K. S., & Braff, D. L. (2002). Endophenotyping schizotypy: a prelude to genetic studies within the schizophrenia spectrum. Schizophrenia Research, 54, 47–57. Calkins, M. E., Curtis, C. E., Grove, W. M., & Iacono, W. G. (2004). Multiple dimensions of schizotypy in first degree biological relatives of schizophrenia patients. Schizophrenia Bulletin, 30, 317–325.

M. Kiang / Journal of Neurolinguistics 23 (2010) 193–203

201

Catts, S. V., Fox, A. M., Ward, P. B., & McConaghy, N. (2000). Schizotypy: phenotypic marker as risk factor. Australia & New Zealand Journal of Psychiatry, 34(Suppl.), S101–S107. Chang, B. P., & Lenzenweger, M. F. (2005). Somatosensory processing and schizophrenia liability: exteroceptive sensitivity, and graphesthesia performance in the biological relatives of schizophrenia patients. Journal of Abnormal Psychology, 114, 85–95. Chapman, J. P., Chapman, L. J., & Kwapil, T. R. (1995). Scales for the measurement of schizotypy. In A. Raine, T. Lencz, & S. A. Mednick (Eds.), Schizotypal personality. Cambridge, UK: Cambridge University Press. Chapman, L. J., Chapman, J. P., & Raulin, M. L. (1976). Scales for physical and social anhedonia. Journal of Abnormal Psychology, 85, 374–382. Chapman, L. J., Chapman, J. P., & Raulin, M. L. (1978). Body-image aberration in Schizophrenia. Journal of Abnormal Psychology, 87, 399–407. Chiarello, C., Burgess, C., Richards, L., & Pollock, A. (1990). Semantic and associative priming in the cerebral hemispheres: some words do, some words don’t. sometimes, some places. Brain and Language, 38, 75–104. Coleman, M. J., Levy, D. L., Lenzenweger, M. F., & Holzman, P. S. (1996). Thought disorder, perceptual aberrations, and schizotypy. Journal of Abnormal Psychology, 105, 469–473. Collins, A. M., & Loftus, E. F. (1975). A spreading-activation theory of semantic processing. Psychological Review, 82, 407–428. Compton, M. T., Chien, V. H., & Bollini, A. M. (2007). Psychometric properties of the brief version of the Schizotypal Personality Questionnaire in relatives of patients with schizophrenia-spectrum disorders and non-psychiatric controls. Schizophrenia Research, 91, 122–131. Coulson, S., & Williams, R. F. (2005). Hemispheric asymmetries and joke comprehension. Neuropsychologia, 43, 128–141. Deacon, D., Uhm, T. J., Ritter, W., Hewitt, S., & Dynowska, A. (1999). The lifetime of automatic semantic priming effects may exceed two seconds. Brain Research: Cognitive Brain Research, 7, 465–472. Eckblad, M., & Chapman, L. J. (1983). Magical ideation as an indicator of schizotypy. Journal of Consulting and Clinical Psychology, 51, 215–225. Edell, W. S. (1987). Role of structure in disordered thinking in borderline and schizophrenic disorders. Journal of Personality Assessment, 51, 23–41. Fisher, J. E., Heller, W., & Miller, G. A. (2007). Semantic associations, lateralized frontal function, and context maintenance in schizotypy. Neuropsychologia, 45, 663–672. Goldman-Rakic, P. S., & Selemon, L. D. (1997). Functional and anatomical aspects of prefrontal pathology in schizophrenia. Schizophrenia Bulletin, 23, 437–458. Hill, H., Ott, F., & Weisbrod, M. (2005). SOA-dependent N400 and P300 semantic priming effects using pseudoword primes and a delayed lexical decision. International Journal of Psychophysiology, 56, 209–221. Holcomb, P. J., & Neville, H. J. (1991). Natural speech processing: an analysis using event-related brain potentials. Psychobiology, 19, 286–300. Ingraham, L. J. (1995). Family-genetic research and schizotypal personality. In A. Raine, T. Lencz, & S. A. Mednick (Eds.), Schizotypal personality (pp. 19–42). Cambridge, UK: Cambridge University Press. Janowsky, D. S., Huey, L., Storms, L., & Judd, L. L. (1977). Methylphenidate hydrochloride effects on psychological tests in acute schizophrenic and nonpsychotic patients. Archives of General Psychiatry, 34, 189–194. Johnson, D. E., & Shean, G. D. (1993). Word associations and schizophrenic symptoms. Journal of Psychiatric Research, 27, 69–77. Jones, L. A., Cardno, A. G., Murphy, K. C., Sanders, R. D., Gray, M. Y., McCarthy, G., et al. (2000). The kings schizotypy questionnaire as a quantitative measure of schizophrenia liability. Schizophrenia Research, 45, 213–221. Kendler, K. S., Gruenberg, A. M., & Kinney, D. K. (1994). Independent diagnoses of adoptees and relatives as defined by DSM-III in the provincial and national samples of the Danish adoption study of schizophrenia. Archives of General Psychiatry, 51, 456–468. Kendler, K. S., Lieberman, J. A., & Walsh, D. (1989). The structured interview for schizotypy (SIS): a preliminary report. Schizophrenia Bulletin, 15, 559–571. Kendler, K. S., McGuire, M., Gruenberg, A. M., & Walsh, D. (1995). Schizotypal symptoms and signs in the roscommon family study. Their factor structure and familial relationship with psychotic and affective disorders. Archives of General Psychiatry, 52, 296–303. Kendler, K. S., Thacker, L., & Walsh, D. (1996). Self-report measures of schizotypy as indices of familial vulnerability to schizophrenia. Schizophrenia Bulletin, 22, 511–520. Kerns, J. G., & Berenbaum, H. (2000). Aberrant semantic and affective processing in people at risk for psychosis. Journal of Abnormal Psychology, 109, 728–732. Kety, S. S. (1983). Mental illness in the biological and adoptive relatives of schizophrenic adoptees: findings relevant to genetic and environmental factors in etiology. American Journal of Psychiatry, 140, 720–727. Kiang, M., & Kutas, M. (2005). Association of schizotypy with semantic processing differences: an event-related brain potential study. Schizophrenia Research, 77, 329–342. Kiang, M., & Kutas, M. (2006). Abnormal typicality of responses on a category fluency task in schizotypy. Psychiatry Research, 145, 119–126. Kimble, M., Lyons, M., O’Donnell, B., Nestor, P., Niznikiewicz, M., & Toomey, R. (2000). The effect of family status and schizotypy on electrophysiologic measures of attention and semantic processing. Biological Psychiatry, 47, 402–412. Koenigsberg, H. W., Buchsbaum, M. S., Buchsbaum, B. R., Schneiderman, J. S., Tang, C. Y., New, A., et al. (2005). Functional MRI of visuospatial working memory in schizotypal personality disorder: a region-of-interest analysis. Psychological Medicine, 35, 1019–1030. Kravetz, S., Faust, M., & Edelman, A. (1998). Dimensions of schizotypy and lexical decision in the two hemispheres. Personality and Individual Differences, 25, 857–871. Kremen, W. S., Faraone, S. V., Toomey, R., Seidman, L. J., & Tsuang, M. T. (1998). Sex differences in self-reported schizotypal traits in relatives of schizophrenic probands. Schizophrenia Research, 34, 27–37. Kutas, M. (1985). ERP comparisons of the effects of single word and sentence contexts on word processing. Psychophysiology, 22, 575–576. Kutas, M., & Federmeier, K. D. (2000). Electrophysiology reveals semantic memory use in language comprehension. Trends in Cognitive Sciences, 4, 463–470.

202

M. Kiang / Journal of Neurolinguistics 23 (2010) 193–203

Kutas, M., & Hillyard, S. A. (1980). Reading senseless sentences: brain potentials reflect semantic incongruity. Science, 207, 203– 205. Lenzenweger, M. F. (2006). Schizotaxia, schizotypy, and schizophrenia: Paul E. Meehl’s blueprint for the experimental psychopathology and genetics of schizophrenia. Journal of Abnormal Psychology, 115, 195–200. Lenzenweger, M. F., Miller, A. B., Maher, B. A., & Manschreck, T. C. (2007). Schizotypy and individual differences in the frequency of normal associations in verbal utterances. Schizophrenia Research, 95, 96–102. Leonhard, D., & Brugger, P. (1998). Creative, paranormal, and delusional thought: a consequence of right hemisphere semantic activation? Neuropsychiatry, Neuropsychology and Behavioural Neurology, 11, 177–183. MacDonald, A. W., 3rd, Carter, C. S., Kerns, J. G., Ursu, S., Barch, D. M., Holmes, A. J., et al. (2005). Specificity of prefrontal dysfunction and context processing deficits to schizophrenia in never-medicated patients with first-episode psychosis. American Journal of Psychiatry, 162, 475–484. McCarley, R. W., Niznikiewicz, M. A., Salisbury, D. F., Nestor, P. G., O’Donnell, B. F., Hirayasu, Y., et al. (1999). Cognitive dysfunction in schizophrenia: unifying basic research and clinical aspects. European Archives of Psychiatry and Clinical Neuroscience, 249(Suppl. 4), 69–82. McClure, M. M., Barch, D. M., Flory, J. D., Harvey, P. D., & Siever, L. J. (2008). Context processing in schizotypal personality disorder: evidence of specificity of impairment to the schizophrenia spectrum. Journal of Abnormal Psychology, 117, 342–354. McClure, M. M., Barch, D. M., Romero, M. J., Minzenberg, M. J., Triebwasser, J., Harvey, P. D., et al. (2007). The effects of guanfacine on context processing abnormalities in schizotypal personality disorder. Biological Psychiatry, 61, 1157–1160. Meehl, P. (1962). Schizotaxia, schizotypy, schizophrenia. The American Psychologist, 17, 827–838. Merten, T. (1993). Word association responses and psychoticism. Personality and Individual Differences, 14, 837–839. Miller, E. N., & Chapman, L. J. (1983). Continued word association in hypothetically psychosis-prone college students. Journal of Abnormal Psychology, 92, 468–478. Minzenberg, M. J., Ober, B. A., & Vinogradov, S. (2002). Semantic priming in schizophrenia: a review and synthesis. Journal of the International Neuropsychological Society, 8, 699–720. Mitchell, R. L., & Crow, T. J. (2005). Right hemisphere language functions and schizophrenia: the forgotten hemisphere? Brain, 128, 963–978. Mitropoulou, V., Harvey, P. D., Zegarelli, G., New, A. S., Silverman, J. M., & Siever, L. J. (2005). Neuropsychological performance in schizotypal personality disorder: importance of working memory. American Journal of Psychiatry, 162, 1896–1903. Mohr, C., Graves, R. E., Gianotti, L. R., Pizzagalli, D., & Brugger, P. (2001). Loose but normal: a semantic association study. Journal of Psycholinguistic Research, 30, 475–483. Morgan, C., Bedford, N., & Rossell, S. L. (2006). Evidence of semantic disorganisation using semantic priming in individuals with high schizotypy. Schizophrenia Research, 84, 272–280. Moritz, S., Andresen, B., Domin, F., Martin, T., Probsthein, E., Kretschmer, G., et al. (1999). Increased automatic spreading activation in healthy subjects with elevated scores in a scale assessing schizophrenic language disturbances. Psychological Medicine, 29, 161–170. Nakamura, M., McCarley, R. W., Kubicki, M., Dickey, C. C., Niznikiewicz, M. A., Voglmaier, M. M., et al. (2005). Fronto-temporal disconnectivity in schizotypal personality disorder: a diffusion tensor imaging study. Biological Psychiatry, 58, 468–478. Neely, J. (1977). Semantic priming and retrieval from lexical memory: roles of inhibitionless spreading activation and limitedcapacity attention. Journal of Experimental Psychology, 106, 226–254. Nelson, D.L., McEvoy, C.L., Schreiber, T.A. (1999). The University of South Florida word association norms [Electronic Version]. Available at w3.usf.edu/FreeAssociation. Niznikiewicz, M. A., Friedman, M., Shenton, M. E., Voglmaier, M., Nestor, P. G., Frumin, M., et al. (2004). Processing sentence context in women with schizotypal personality disorder: an ERP study. Psychophysiology, 41, 367–371. Niznikiewicz, M. A., Shenton, M. E., Voglmaier, M., Nestor, P. G., Dickey, C. C., Frumin, M., et al. (2002). Semantic dysfunction in women with schizotypal personality disorder. American Journal of Psychiatry, 159, 1767–1774. Niznikiewicz, M. A., Voglmaier, M., Shenton, M. E., Seidman, L. J., Dickey, C. C., Rhoads, R., et al. (1999). Electrophysiological correlates of language processing in schizotypal personality disorder. American Journal of Psychiatry, 156, 1052–1058. Palermo, D., & Jenkins, J. J. (1970). Word association norms. New York: Academic Press. Pizzagalli, D., Lehmann, D., & Brugger, P. (2001). Lateralized direct and indirect semantic priming effects in subjects with paranormal experiences and beliefs. Psychopathology, 34, 75–80. Rado, S. (1953). Dynamics and classification of disordered behavior. American Journal of Psychiatry, 110, 406–416. Raine, A. (1991). The SPQ: a scale for the assessment of schizotypal personality based on DSM-III-R criteria. Schizophrenia Bulletin, 17, 555–564. Roediger, H. L., & McDermott, K. B. (1995). Creating false memories: remembering words not presented in lists. Journal of Experimental Psychology: Learning Memory and Cognition, 21, 803–814. Servan-Schreiber, D., Cohen, J. D., & Steingard, S. (1996). Schizophrenic deficits in the processing of context. A test of a theoretical model. Archives of General Psychiatry, 53, 1105–1112. Shakow, D. (1980). Kent-Rosanoff association and its implications for segmental set theory. Schizophrenia Bulletin, 6, 676–685. Siever, L. J., & Davis, K. L. (2004). The pathophysiology of schizophrenia disorders: perspectives from the spectrum. American Journal of Psychiatry, 161, 398–413. Solovay, M. R., Shenton, M. E., Gasperetti, C., Coleman, M., Kestnbaum, E., Carpenter, J. T., et al. (1986). Scoring manual for the thought disorder index. Schizophrenia Bulletin, 12, 483–496. Sommer, I. E., Ramsey, N. F., & Kahn, R. S. (2001). Language lateralization in schizophrenia, an fMRI study. Schizophrenia Research, 52, 57–67. Spitzer, M. (1997). A cognitive neuroscience view of schizophrenic thought disorder. Schizophrenia Bulletin, 23, 29–50. Spreen, O., & Strauss, E. (1998). A compendium of neuropsychological tests (2nd ed.). New York: Oxford University Press. Stelmack, R. M., & Miles, J. (1990). The effect of picture priming on event-related potentials of normal and disabled readers during a word recognition memory task. Journal of Clinical and Experimental Neuropsychology, 12, 887–903. Titone, D. (1998). Hemispheric differences in context sensitivity during lexical ambiguity resolution. Brain and Language, 65, 361–394.

M. Kiang / Journal of Neurolinguistics 23 (2010) 193–203

203

Torgersen, S., Kringlen, E., & Cramer, V. (2001). The prevalence of personality disorders in a community sample. Archives of General Psychiatry, 58, 590–596. Tsuang, M. T., Stone, W. S., & Faraone, S. V. (2000). Toward reformulating the diagnosis of schizophrenia. American Journal of Psychiatry, 157, 1041–1050. Tsuang, M. T., Stone, W. S., Tarbox, S. I., & Faraone, S. V. (2002). An integration of schizophrenia with schizotypy: identification of schizotaxia and implications for research on treatment and prevention. Schizophrenia Research, 54, 169–175. Vaever, M. S., Licht, D. M., Moller, L., Perlt, D., Jorgensen, A., Handest, P., et al. (2005). Thinking within the spectrum: schizophrenic thought disorder in six Danish pedigrees. Schizophrenia Research, 72, 137–149. Vollema, M. G., Sitskoorn, M. M., Appels, M. C., & Kahn, R. S. (2002). Does the Schizotypal Personality Questionnaire reflect the biological-genetic vulnerability to schizophrenia? Schizophrenia Research, 54, 39–45. Ward, P. B., McConaghy, N., & Catts, S. V. (1991). Word association and measures of psychosis proneness in university students. Personality and Individual Differences, 12, 473–480. Weiss, E. M., Hofer, A., Golaszewski, S., Siedentopf, C., Brinkhoff, C., Kremser, C., et al. (2004). Brain activation patterns during a verbal fluency test-a functional MRI study in healthy volunteers and patients with schizophrenia. Schizophrenia Research, 70, 287–291. Yaralian, P. S., Raine, A., Lencz, T., Hooley, J. M., Bihrle, S. E., Mills, S., et al. (2000). Elevated levels of cognitive-perceptual deficits in individuals with a family history of schizophrenia spectrum disorders. Schizophrenia Research, 46, 57–63.