Verbal Fluency Esquizotipia

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Verbal fluency in schizotypy

Less words, more words: psychometric schizotypy and verbal fluency1

Elias Tsakanikos and Cordon Claridge

Abstract

Positive and negative symptoms of schizophrenia have been differentially associated

with irregularities in verbal production, suggesting the involvement of different

underlying mechanisms in psychotic symptomatology. In view of that, the present

investigation examined whether the amount of verbal production would be also

differentially associated with negative and positive symptoms of psychometric

schizotypy in a sample of college students (N=190). The participants were tested on

a typical verbal fluency test and completed the O-LIFE schizotypy scales. The

analyses revealed that decreased verbal fluency was associated with increased levelsof negative schizotypy in participants who scored one standard deviation above the

mean on the Introvertive Anhedonia scale. In contrast, increased verbal fluency

was associated with increased levels of positive schizotypy in participants who

scored one standard deviation above the mean on the Unusual Experiences scale.

The obtained results are discussed in terms of the proposal that psychotic-like

unusual experiences, like hallucinations, may be the product of a higher automatic

spreading activation among stored lexical units, a mechanism which seems to

account for the previously reported link between positive schizotypy and creativity.

Key words: automatic spreading activation; creativity; executive functioning;hallucinations; phonological (letter) fluency; positive/negative schizotypy; individualdifferences in speech production

Abnormalities in verbal communication, such as irregularities in speech production,are frequent in people with schizophrenia. Dramatic fluctuations between increase(pressure of speech) and decrease (poverty of speech) in the amount of verbal

production have been related to linguistic impairments in schizophrenia, and havebeen consistently associated with different aspects of the psychotic symptomatology(Harvey, 2000). Despite the presence of a wide range of communication abnormalitiesin schizophrenia, factor analytic studies have identified verbal productivity as a main

dimension of communication disorder (Harvey, Lenzenweger, Keefe, Pogge, Serper,& Mohs, 1992).

Poor performance on verbal fluency, as assessed by the ability to generate wordlists under certain stimulus constraints, has been associated with negative symptomsof schizophrenia, such as flat affect, anhedonia, and impoverished speech (Allen,Liddle & Frith, 1993; Howanitz, Cicalese, & Harvey, 2000). Verbal fluency isthought to reflect executive functioning, such as cognitive switching, rule monitoring,and inhibition of inappropriate responses (Lezak, 1995). Impaired executivefunctioning has not only been associated with deficient frontal lobe functioning inschizophrenia (Crow, 1992), but also with frontal lobe dysfunction in other patient

1Tsakanikos, E. & Claridge, G. (2004). Less words, more words: psychometric schizotypy and verbalfluency. Manuscript submitted for publication.

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groups (Beatty, Goodkin, & Beatty, 1989; Joyce & Robbins, 1991). Tests of verbalfluency are generally considered to be sensitive to frontal lobe dysfunction (Lezak,1995) as well.

Evidence suggests that verbal fluency is differentially affected in psychosis.Although poor performance has been associated with negative symptomatology

(Allen et al., 1993; Howanitz et al., 2000), increased verbal fluency has beenassociated with positive psychotic symptoms, such as hallucinations (Lindamer &Whitman, 1997; Kerns, Berenbaum, Barch, Banich, & Stolar, 1999). This latterfinding is consistent with theoretical proposals that hallucinations are produced as aresult of an increased automatic spreading activation between stored lexical items(David, 1994; Hoffman & McGlashan, 1997). People who experience hallucinationsmay generate an increased amount of words during verbal fluency tests due to such anenhanced lexical activation.

Are irregularities in verbal fluency primary or secondary features of psychosis?Cognitive irregularities in schizophrenia can be either viewed as cognitiveendophenotypes (primary features), i.e. cognitive markers intermediating between a

putative genetic disposition and clinical symptoms, or as epiphenomena of thepsychotic symptoms, side effects due to medication, and/or effects of hospitalization(secondary features). The presence of verbal fluency abnormalities in healthy

participants who score highly on psychometric measures of schizotypy would supportthe possibility that these irregularities are primary features. On the contrary, anegative result would suggest that these irregularities are secondary features.Unfortunately, because of conflicting evidence in the recent literature, it is unclearwhether or not verbal fluency irregularities, akin to those associated with negative and

positive symptoms of schizophrenia, can be observed in positive and negativeschizotypy as well.

In some recent studies, positive schizotypy has been associated with increasedverbal fluency (OReilly, Dunbar, & Bentall, 2001; Weinstein & Graves, 2002).Considering that fluency is typically regarded as a main facet of creativity, the authorsof these studies have interpreted this association as evidence of a biological link

between creativity and positive psychotic-like features (e.g. aberrant perceptualexperiences). This reported association between positive schizotypy and increasedverbal fluency (OReilly et al., 2001; Weinstein & Graves, 2002) seems to accordwith the hypothesis that hallucinations are the product of an increased automaticspreading activation between related lexical units (David, 1994; Hoffman &McGlashan, 1997). However, other studies have failed to demonstrate a similarassociation between positive schizotypy and verbal fluency (Barrantes-Vidal,

Fananas, Rosa, Caparros, Riba, & Obiols, 2002; Dinn, Harris, Aycicegi, Greene, &Andover,2002). In addition, unlike the schizophrenia literature (Allen et al., 1993;Howanitz et al., 2000), none of the above schizotypy studies (Barrantes-Vidal et al.,2002; Dinn et al., 2002; OReilly et al., 2001; Weinstein & Graves, 2002) haverevealed any specific association between poor performance on verbal fluency andnegative schizotypy.

One possible explanation for the above inconsistent results might be related tothe sample size. With the exception of the Barrantes-Vidal et al study, whichemployed a sample of adolescents with mean age = 13.4 years (a methodological

pitfall, considering that the schizotypy scales employed were designed for adults), instudies with adults (Dinn et al., 2002; OReilly et al., 2001;Weinstein & Graves,

2002) the largest sample size was 103 participants. Therefore, the aim of theinvestigation was to re-examine the relationship between verbal fluency and

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positive/negative schizotypy in a larger adult sample. Moreover, any systematicrelationship between verbal fluency and schizotypy might not be necessarily linear.For instance, a differential association between positive/negative schizotypy andverbal fluency may be detectable only for the extreme scorers. Consequently, thesecond aim was to look for evidence on possible non-linear markers. To evaluate the

above possibilities, 190 participants were tested on a typical verbal fluency test(Lezak, 1995) and completed a multi-dimensional schizotypy inventory (O-LIFE;Mason, Claridge, & Jackson, 1995).

MethodParticipantsOne hundred and ninety students, recruited from the University College London(UCL) campus, took part in this study. Their mean age was 23.5 years, ninety-ninewere female, and were unpaid volunteers. English as a second language was anexclusion criterion. Four participants were dropped from the analysis due to a largenumber of unanswered questions in the O-LIFE.

Schizotypy measuresThe OxfordLiverpool Inventory for Feelings and Experiences (O-LIFE) consists of159 items selected on the basis of factor-analytic studies of older schizotypy scales(Bentall, Claridge, & Slade, 1989; Mason et al., 1995). The inventory includes fourschizotypy measures: The Unusual Experiences (positive schizotypy) scale consistsof items assessing magical thinking, unusual perceptual aberrations, and hallucinatoryexperiences. The Cognitive Disorganization (disorganized schizotypy) scalereflectsthe disorganized aspect of psychosis, and consists of items assessing difficulties withconcentration, decision-making and social anxiety. The Introvertive Anhedonia(negative schizotypy) scale reflects the negative symptoms of psychosis, and consistsof items assessing the lack of enjoyment from social contact, physical activities,coupled with aversion to emotional and physical intimacy. Impulsive Non-conformity is largely based on thePsychoticism scale (Eysenck & Eysenck, 1975),and consists of items assessing aggressive, anti-social and impulsive behaviour.

Attesting to the experimental validity of these scales, high-schizotypy scorers, asidentified by the O-LIFE sub-scales, demonstrate neuro-cognitive deficits akin tothose seen in schizophrenic patients (Steel, Hemsley, & Jones, 1996; Rawlings &Goldberg, 2001; Tsakanikos & Reed, 2003).

Verbal fluencyA phonological (letter) fluency task, frequently used in neuropsychological research

(Lezak, 1995), was employed to assess verbal fluency. The task consisted of three 1min trials. In each trial, the participants were asked to generate as many words aspossible that started with a certain letter (C, F, and L), avoiding names, non-Englishwords, and derivatives of the same word. The total number of correct responsesgenerated was the dependent measure.

Results

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Table 1 about here

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Data from Table 1 presents the means, the standard deviations, and the inter-correlations between the O-LIFE scales, and verbal fluency. In terms of the O-LIFEscales, the overall pattern (inter-correlation and descriptive statistics) appeared similar

to that reported in the original study (Mason et al., 1995), as well as to that reported inlater studies (e.g., Rawlings & Goldberg, 2001; Tsakanikos & Reed, 2003). It should

be noted that the only exception was the absence of a significant correlation betweenImpulsivity Non-conformity and Introvertive Anhedonia (in the original study, r=-0.10, p< 0.05). Considering that the correlation between the two scales was quitelow in both studies, this deviation was probably due sample size differences betweenthe Mason et al study (N = 508) and the present investigation (N = 186). Contrary towhat was expected, there was no significant correlation between schizotypy scalesand verbal fluency.

Despite the absence of a statistically significant correlation between schizotypyscales and verbal fluency, it could be still argued that non-linear relationships between

these measures may exist. For example, particular trends between verbal fluency anddifferent schizotypy measures may exist only for participants with very highschizotypy scores. To investigate the above possibility, verbal fluency performancewas plotted as a function of positive and negative schizotypy (Figure 1).

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Figure 1 about here

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Inspection of the upper graph (Figure 1 - panel A) suggests that, for participantswho scored one standard deviation above the mean on positive schizotypy (UnusualExperiences > 15), verbal fluency appeared to increase as a function of theirschizotypy scores. For these extreme high scorers (N= 33), there was a statisticallysignificant positive correlation between Unusual Experiences and verbal fluency (r= 0.35, P< 0.05). However, there was no significant correlation between UnusualExperiences and verbal fluency (r = 0.03, P > 0.80) for participants scoring onestandard deviation below the mean (Unusual Experiences < 5).

Inspection of the lower graph (Figure 1 - panel B), suggested that verbal fluencyappeared to decrease as a function of negative schizotypy for participants who scored

one standard deviation above the mean (> 8) on Introvertive Anhedonia. For thoseextreme scorers (N= 28), there was a statistically significant negative correlationbetween Introvertive Anhedonia and verbal fluency (r = 0.46, P < 0.05). Forthose participants who scored on negative schizotypy one standard deviation belowthe mean (Introvertive Anhedonia < 3), there was no significant correlation betweenIntrovertive Anhedonia and verbal fluency (r = 0.01, P > 0.90). The obtainedresults suggest that verbal fluency, at least for those who scored very high onschizotypy, was positively associated with positive schizotypy, and negativelyassociated with negative schizotypy2.

2The same analyses run for extreme scorers on Cognitive Disorganization and Impulsivity Non-conformity, but no evidence for similar non-linear markers were found.

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Discussion

In line with the schizophrenia literature (Allen et al., 1993; Howanitz et al., 2000;

Lindamer & Whitman, 1997; Kerns et al., 1999), the present data suggested thatdifferent schizotypy dimensions were differentially associated with verbal

productivity, as assessed by a typical letter fluency task. However, the relationshipbetween verbal fluency and schizotypy was not linear; these associations were presentonly for those participants who scored one standard deviation above the mean. It isworth noting that this finding supports quasi-dimensional rather fully dimensionalviews of schizotypy (see Claridge, 1997, for a discussion). In addition, the fact thatdifferentiated verbal fluency irregularities were observed in a student sample as afunction of psychometric schizotypy suggests that such irregularities are cognitivemarkers (primary features) rather than epiphenomena (secondary features) of

psychosis.

During the phonological (letter) task, the participants were asked to generate asmany words as possible by following certain rules, i.e. the words should start with acertain letter, and derivatives of the same words, names, and non-English wordsshould be avoided. Consequently, adequate word production in this task relied largelyon executive functions, such as maintaining on-line these rules and monitoring

performance accordingly, while inhibiting inappropriate responses (Lezak, 1995). Inthe present study, negative schizotypy was found to be associated with decreasedverbal fluency, following the pattern of the negative symptoms of schizophrenia(Allen et al., 1993; Howanitz et al., 2000). Given that negative symptoms ofschizophrenia have been associated with impaired executive functions (Crow, 1992),it is possible that similar subtle impairments had a detrimental effect on verbalinfluence in participants scoring highly on negative schizotypy.

However, apart from executive functions, another cognitive process that is highlyrelevant to performance on a verbal fluency task is the speed of lexical retrieval. A

particularly increased activation of stored lexical units would, therefore, be expectedto enhance performance on a letter fluency task. Certain positive symptoms ofschizophrenia, such as hallucinations, have been attributed to such an increasedautomatic spreading activation of related lexical items3 (David, 1994; Hoffman &McGlashan, 1997). Given that positive symptoms of schizophrenia have beenassociated with increased verbal fluency (Lindamer & Whitman, 1997; Kerns et al.,1999), it is possible that both positive symptoms and increased verbal fluency may be

products of an enhanced automatic spreading activation. Such an account could alsoaccommodate the finding that high levels of positive schizotypy are associated withincreased verbal fluency, as has been shown in previous studies (OReilly et al.,2001;Weinstein & Graves, 2002) and replicated in the present investigation.

It could be argued that the positive association between verbal fluency andpositive schizotypy is also predicted by the sheer inhibition hypothesis (Spitzer,1993). According to this hypothesis, activation tends to spread more diffusely andmore rapidly due to inadequate mechanisms that control spreading activation and re-activation in the semantic networks. Unlike the automatic spreading activation

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For instance, a neutral sound activates automatically a similar sounding word, which in turn activatesinstantly and simultaneously other semantically or/and phonetically related words etc.

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account, which seems limited to semantically and/or phonetically related lexical units(David, 1994; Hoffman & McGlashan, 1997), the sheer inhibition hypothesis is notlimited to certain types of units (Spitzer, 1993). Nevertheless, the two accounts arenot necessarily incompatible; for example, an over-activation of phonetically relatedlexical units, which has been proposed to be responsible for the production of acoustic

hallucinations (David, 1994; Hoffman & McGlashan, 1997), could be due toinefficient control mechanisms of spreading activation and re-activation in thesemantic networks (Spitzer, 1993).

In summary, the present investigation showed that personality traits thatphenomenonologically resemble the negative and positive symptoms of schizophreniawere differentially related to verbal fluency, suggesting different underlyingmechanisms. Enhanced performance on verbal fluency was associated with highlevels of positive schizotypy, i.e. increased reports of hallucination-like experiences,delusional ideation, and perceptual aberrations, a pattern of results predicted bytheories of increased automatic spreading activation in the semantic networks (David,1994; Hoffman & McGlashan, 1997; Spitzer, 1993). Given that verbal fluency is a

main facet of creativity, the obtained results reinforce the notion that the link betweenpathological personality traits and creativity is likely due to common cognitivefeatures (Eysenck, 1993). This notion is consistent with the possibility of a healthyschizotypy (McCreery & Claridge, 2002), which may account for the persistence ofschizophrenia-related genes in the population despite their many dysfunctionalaspects.

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Acknowledgements

Thanks are due to Carmen Chan, Emma Coakley, Helen Fisher, Suzanne Gage,Jacqlin Iaccovou, Samaira Khan, James MacDonald, Hannah Pratt, Alexandra Suzuki,Jessica Webb, and Grace Wong for their help with the data collection.

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Table 1Inter-correlations between schizotypy scales and performance on verbal fluency

M SD 1 2 3 4 5

Unusual Experiences 9.72 5.92 -

Cognitive Disorganization 11.71 5.31 0.49** -

Introvertive Anhedonia 4.83 3.69 0.15* 0.09 -

Impulsive Non-conformity 10.17 4.07 0.39** 0.27** -0.04 -

Verbal Fluency 41.64 9.57 0.02 -0.12 -0.05 -0.09 -

*p < 0.05 (two-tailed)**p < 0.01 (two-tailed)

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Figure 1

positive schizotypy ('Unusual Experiences')

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negative schizotypy ('Introvertive Anhedonia')

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Verbal Fluency Esquizotipia

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