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Behaviour Research and Therapy 45 (2007) 1255–1269

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Jumping to conclusions and the continuum of delusional beliefs

Debbie M. Warmana,�, Paul H. Lysakerb, Joel M. Martinc, Louanne Davisb,Samantha L. Haudenschielda

aSchool of Psychological Sciences, University of Indianapolis, 1400 East Hanna Avenue, Indianapolis, IN 46227, USAbRoudebush VA Medical Center and Indiana School of Medicine, Department of Psychiatry, 1481 West 10th Street,

Indianapolis, IN 46202, USAcDepartment of Psychology, Butler University, 4600 Sunset Avenue, Indianapolis, IN 46208, USA

Received 10 May 2006; received in revised form 1 September 2006; accepted 6 September 2006

Abstract

The present study examined the jumping to conclusions reasoning bias across the continuum of delusional ideation by

investigating individuals with active delusions, delusion prone individuals, and non-delusion prone individuals. Neutral

and highly self-referent probabilistic reasoning tasks were employed. Results indicated that individuals with delusions

gathered significantly less information than delusion prone and non-delusion prone participants on both the neutral and

self-referent tasks, (po.001). Individuals with delusions made less accurate decisions than the delusion prone and non-

delusion prone participants on both tasks (po.001), yet were more confident about their decisions than were delusion

prone and non-delusion prone participants on the self-referent task (p ¼ .002). Those with delusions and those who were

delusion prone reported higher confidence in their performance on the self-referent task than they did the neutral task

(p ¼ .02), indicating that high self-reference impacted information processing for individuals in both of these groups. The

results are discussed in relation to previous research in the area of probabilistic reasoning and delusions.

r 2006 Elsevier Ltd. All rights reserved.

Keywords: Delusions; Reasoning; Psychosis; Cognitive

Introduction

Reasoning studies have been instrumental in uncovering how those with delusions make decisions.Experimental tasks have demonstrated robust evidence that those with delusions jump to conclusions onprobabilistic reasoning tasks (Dudley, John, Young, & Over, 1997a; Garety, Hemsely, & Wessely, 1991; Huq,Garety, & Hemsley, 1988; Moritz & Woodward, 2005). Individuals with delusions request minimalinformation in situations where information is available, yet report a high level of confidence in their decisions(Huq et al., 1988). Such findings have led to theories of delusion formation and maintenance, speculating thatthe jumping to conclusions reasoning style is a likely factor in the acquisition of delusional beliefs and that

e front matter r 2006 Elsevier Ltd. All rights reserved.

at.2006.09.002

ing author. Tel.: +1317 788 2102; fax: +1 317 788 2120.

ess: dwarman@unidy.edu (D.M. Warman).

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once acquired, such reasoning strategies serve to maintain false beliefs (Garety & Freeman, 1999; Van Dael etal., in press).

To assess how individuals make decisions on neutral tasks of probabilistic reasoning, a ‘‘beads task’’ is oftenemployed (e.g., Huq et al., 1988). For this task, participants are shown two jars of beads, one with 85 beads ofcolor A and 15 beads of color B and a second jar of 100 beads, but with the colors in the opposite ratio.Participants are shown beads, one at a time, until they report they are ready to decide which jar the beads arecoming from. Studies have demonstrated that, compared to both psychiatric control groups and healthycontrols, those with delusions request minimal information before making a decision (Dudley, John, Young,& Over, 1997b; Huq et al., 1988, Peters & Garety, 2006). This jumping to conclusions bias has also beendemonstrated on tasks that are more difficult, by using a 60:40 ratio instead of 85:15 (Dudley et al., 1997b).Such studies have shown that while task difficulty increases the amount of information those with delusionsrequest, they still jump to conclusions when compared to those without delusions. Given that task difficulty isrelated to gathering more information, it does not appear that the jumping to conclusions bias is an artifact ofjust being more impulsive in making decisions; rather, it appears that those with delusions are, indeed,attempting to reason effectively. Their use of reasoning strategies, however, can be considered faulty, as theyarrive at conclusions so quickly.

One advantage of using beads as stimuli in investigations of decision making is that the stimuli areemotionally neutral; this helps to ensure that general reasoning is being studied, as opposed to reasoning underconditions of heightened emotion. Still, how individuals with delusions reason about emotional material isalso of interest. Dudley et al. (1997a) modified the beads task to make it self-referent, which was theorized tobe emotionally salient. In their task, beads were replaced with survey comments. They told their participantsthat two surveys had been conducted about a person very much like the participant. One of the surveysresulted in 60 positive and 40 negative comments and the second survey resulted in 60 negative comments and40 positive comments. Participants were told one survey comment at a time and were instructed to tell theexperimenter when they heard enough words to make a decision about which survey (i.e., the mostly positiveor the mostly negative survey) the words were coming from. Despite the task being minimally self-referent,when compared to neutral tasks, the emotional task resulted in increased jumping to conclusions. It isexpected that if personal self-reference were heightened, the jumping to conclusions bias would also beincreased.

While the above demonstrates the importance of delusions in relation to the jumping to conclusionsreasoning bias, it is also the case that there is variability, even in those with delusions. Belief flexibility and theability to develop alternatives to delusions appear to be important factors. Freeman et al. (2004) found thatindividuals with delusions who reported no alternative explanations for their beliefs evidenced more of ajumping to conclusions reasoning bias on difficult probabilistic tasks (i.e., 60:40) than those who were able toreport an alternative explanation. Furthermore, Garety et al. (2005) found a significant relationship betweenthe jumping to conclusions reasoning bias and the absence of a recognition of the possibility they may beincorrect about their delusion. In addition, there is evidence that higher conviction in delusional beliefs isassociated with more of a jumping to conclusions reasoning bias (Garety et al., 2005). Thus, it appears thatperhaps there is a continuum of delusional beliefs, from complete conviction to the ability to recognizealternatives, that is of importance when understanding the jumping to conclusions reasoning bias.

Examining the continuum of psychosis has received considerable attention in recent years (e.g., Johns & van Os,2001). Proponents of the continuum perspective note that there are examples of delusional ideation in the non-clinical population that can be seen as lower on the continuum of delusional ideation. One way of investigating thejumping to conclusions bias and how it relates to the continuum of delusional beliefs is to investigate individualswho do not have formal active delusions but who demonstrate some unusual beliefs that are similar in content, butnot in impairment or intensity/conviction, to those who have delusions. To date, only a handful of studies haveexamined reasoning along the continuum of psychosis. Such studies have provided evidence that those who scorehigh on measures of subclinical delusions, also called ‘‘delusion prone,’’ do appear to have some reasoning biasesthat are similar to those with delusions (Linney, Peters, & Ayton, 1998). Colbert and Peters (2002) found that thosewho are delusion prone jump to conclusions on tasks that are neutral in nature. A more recent investigation thatutilized both the neutral beads task and Dudley et al.’s (1997a) personally referent survey task (Warman & Martin,in press) found that those who scored higher on a measure of delusion proneness jumped to conclusions relative to

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those who scored low on the measure for personally self-referent but not for neutral stimuli. A recent studyexamined reasoning on an 85:15 neutral task and included healthy controls, delusion prone individuals, relatives ofindividuals with psychotic disorders, and individuals with psychotic disorders; they found higher psychotic liabilitywas associated with a greater tendency to jump to conclusions (Van Dael et al., in press). It remains unclear howthose with delusions, those who are delusion prone, and those who are not delusion prone would compare to oneanother on difficult neutral tasks and on salient tasks; to date no studies have investigated this continuum in such areasoning study.

In summary, previous research has demonstrated that the jumping to conclusions reasoning bias is presentin individuals with delusions, and preliminary evidence exists that the jumping to conclusions bias is alsoevident in those who score highly on a measure of delusion proneness (Colbert & Peters, 2002; Dudley et al.,1997a,b; Garety et al., 1991; Garety et al., 2005; Huq et al., 1988; Moritz & Woodward, 2005; Peters & Garety,2006; Warman & Martin, in press). To date, no studies have compared actively delusional, delusion prone,and non-delusion prone individuals in the same reasoning study to investigate differences along thiscontinuum for both neutral and salient tasks. Further, the work of Dudley et al. (1997) and Warman andMartin (in press) have demonstrated that those with delusions and those who are delusion prone jump toconclusions when information is personally referent, yet the amount of emotion provoked in those studies waslikely to be minimal. Thus, the present study examined delusional ideation at points along a continuum andinvestigated reasoning on both neutral and emotionally salient tasks. To increase the salience of stimuli,participants were asked to generate descriptions of themselves; those words, rather than predetermined wordswhich were used in previous studies, were used to develop ‘‘surveys’’ that then the participant was told wereabout them. Thus, in addition to increasing the expected relevance of the words heard in the emotionallysalient condition, participants were told the survey was done about them, rather than about a person verymuch like them, increasing the degree of personal reference. It was expected that those who had activedelusions would jump to conclusions relative to both delusion prone and not delusion prone individuals onboth neutral and self-referent tasks and that all individuals would request fewer stimuli on self-referent thanneutral tasks. As delusion proneness can be seen as falling midway along the continuum of delusional ideation,it was expected that those who were delusion prone would demonstrate information gathering strategies thatresulted in less jumping to conclusions than those with active delusions, yet more jumping to conclusions thanthose who were not delusion prone.

Method

Participants

In order to participate in the present study, individuals needed to be at least 18 years of age. Participantswere recruited from two locations: (1) a VA Medical Center; (2) a small liberal arts college in the AmericanMidwest. At the VA, individuals with SCID confirmed diagnoses of schizophrenia or schizoaffective disorderwho were enrolled in a larger study investigating anxiety were invited to participate. Participants with adiagnosis of schizophrenia or schizoaffective disorder needed to report active delusions; they needed to obtaina PANNS score on the delusions component of 3 or above. Thirteen participants were excluded as theyreported no active delusions or had a PANSS score of less than 3. At the college, undergraduate students wererecruited and received course credit for participating. All of the participants with delusions were recruited atthe VA; no participant from the university sample reported a history of psychotic disorder diagnosis. Allparticipants who were classified as delusion prone and not delusion prone were from the university sample.Each participant provided informed consent and voluntarily agreed to participate. Participant characteristicsare summarized in Table 1.

Materials

Measure of delusion proneness

The Peters et al. Delusions Inventory (PDI; Peters, Joseph, & Garety, 1999) assesses delusional ideation in amultidimensional manner in the general population. It examines various experiences on a continuum and is

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Table 1

Participant characteristics by delusion status classification

Active delusions Delusion prone Not delusion prone

N %� N %� N %�

Gender

Male 33 86.8% 6 20% 9 30%

Female 4 10.5% 24 80% 21 70%

Race

Caucasian 18 47.4% 21 70% 28 93.3%

African American 12 31.6% 3 10% 1 3.3%

Other 3 7.9% 6 20% 1 3.3%

Mean (SD) Mean (SD) Mean (SD)

Age 48.1 (6.02) 19.57 (1.41) 23.13 (7.32)

Note: N ¼ 98; Data missing for one participant’s gender (in active delusions group); five participants did not report race (all in active

delusions group).�Percentages are reported for number of participants within each delusion status classification.

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intended for understanding unusual thinking in non-psychotic populations. The PDI is used to determine if anindividual is ‘‘delusion-prone,’’ i.e., demonstrates delusional ideation even if active delusions are not present.The measure includes 40 items that represent unusual thinking. For example, one item reads, ‘‘Do you everfeel as if things in magazines or on TV were written especially for you?’’ For each item the participant endorses‘‘yes,’’ the individual rates on a 1–5 scale: (a) how distressing the thought is to him/her (Distress Rating Scale);(b) how much he/she thinks about it (Preoccupation Rating Scale); and (c) how much he/she believes it to betrue (Conviction Rating Scale). The number of beliefs endorsed can range from 0 to 40. The Distress RatingScale can range from 0 to 200 as can the scores for the Preoccupation and Conviction Rating Scales. When allitems are summed, the possible total score can range from 0 to 640. Previous research suggests the PDIpossesses adequate reliability (a ¼ .88, test-retest reliability ¼ .82) and validity (concurrent validity has beenassessed by examining common variance between this measure and other measures designed to measure asimilar construct and ranged from 33 to 58%; Peters et al., 1999).

Measures of non-psychotic symptomology

Depression. The Beck Depression Inventory—II (BDI-II; Beck, Steer, & Brown, 1996) is a 21-item self-report instrument developed to measure the severity of depression in adults and adolescents. Each itemconsists of four statements reflecting increasing levels of severity for a particular symptom of depression. Thismeasure was modified for the current study in that two items, ‘‘Pessimism’’ and ‘‘Suicidal Thoughts andDying’’ were omitted. These items were omitted due to their sensitive nature for a non-clinical sample. TheBDI has demonstrated high reliability (a ¼ .91) and convergent validity (r ¼ .93; Dozois, Dobson, &Ahnberg, 1998). This measure was administered in order to partial out the influence of psychological factorsother than delusions or delusion proneness (such as depression).

Anxiety. The Beck Anxiety Inventory (BAI; Beck and Steer, 1990) is a 21-item self-report measure of theseverity of anxiety. Each item consists of a somatic or cognitive symptom and 4 response options reflectingincreasing levels of distress. The BAI has demonstrated high reliability (a ¼ .92, test-retest r ¼ .75),convergent validity (r ¼ .51) and discriminant validity (r ¼ .25; Beck, Epstein, Brown, & Steer, 1988). Thismeasure was administered in order to partial out the influence of psychological factors other than delusions ordelusion proneness (such as anxiety).

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Measure of psychotic symptomology

The Positive and Negative Syndrome Scale (PANSS; Kay, Fiszbein, & Opler, 1987) is a 30 item rating scalecompleted by clinically trained research staff at the conclusion of chart review and a semi-structured interview.It is one of the most widely used semi-structured interviews for assessing the wide range of psychopathology inschizophrenia. For the purposes of the present study, if a participant scored a 3 or above on the Delusionsitem, he or she was classified as having delusions. Individuals diagnosed with schizophrenia or schizoaffectivedisorder who scored below a 3 on this item were classified as not having active delusions and were not part ofthe present investigation.

Procedure

Participants were tested individually. The study had four components, all administered by researchassistants of the authors who were given extensive training in the administration of all components of thestudy. Each participant received each component; the order was fixed across participants. Each component isdescribed below.

Emotionally neutral task

The emotionally neutral task was done using a paradigm based on a task developed by Phillips and Edwards(1966). Participants were shown two jars, one containing 60 blue beads and 40 pink beads, and the other jarcontaining the same number of beads but in the opposite ratio. Participants were asked to engage in four trialswhere they chose which jar a bead came from. Beads were selected based on a fixed, predetermined order,which varied across participants. After each bead draw, the participant was asked if he or she wanted to seemore beads or to decide which jar the bead came from. Once the participant decided, the experimenterrequested the participant report his or her level of confidence in the decision made on a 1–100 scale. The beadsequences were as follows, where B indicates a blue bead and P indicates a pink bead was drawn:

Sequence A: B P B P P B P P B P P P P B P P B B P PSequence B: P B P B P P B B B B B P P B B P B P P PSequence C: P B B B P B B B B B P B B P P P P B B BSequence D: P B B B B B P B P P B P P B B B P P B B

Participants were randomly assigned to receive one of four orders: (1) A, B, C, D; (2) C, D, A, B; (3) B, A,D, C; (4) D, C, B, A.

Emotionally salient task word generation (Part I of emotionally salient task)

For the first part of the emotionally salient task, the participant was asked to generate a list of 10 positivewords to describe himself/herself and 10 negative words. If the participant had trouble coming up with words,he/she was shown a list of ‘‘personality-trait words’’ and asked to pick from the list which ones seemed todescribe him/her best. The list of words that was shown to participants has been studied in terms of theirlikability and unlikability (Anderson, 1968) and was the basis for word selection in the paradigm developed byDudley et al. (1997a) for their emotionally salient task. The list was constructed by using the top 50 (highlylikable) and the bottom 50 (highly unlikable) words from Anderson’s list of 555 words. This is consistent withDudley, who utilized the top and bottom 15% of the most liked and the least liked personality traits. For thepresent study, the top and bottom 9% of Anderson’s words were used. After the participant had generated thelist, he/she was asked to rate, on a scale of 1–100 how much he/she believed each word described him/her.While the participant completed the self-reports (see below), the words were ranked by the researcheradministering the protocol from highest to lowest and were used to construct the hypothetical surveys thatwere read aloud to the participant during Part II of the emotionally salient task.

Completion of self-reports

Participants next completed the Beck Depression Inventory-II, the Beck Anxiety Inventory, and the Peterset al. Delusions Inventory. For the majority of the participants with schizophrenia and schizoaffective

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disorder, the BDI and the BAI were done at a previous testing session as part of the larger study they wereenrolled in, in an effort to reduce fatigue. However, all participants completed at least the PDI during thiscomponent of the testing session for the present study. For the undergraduate students, all self-reports wereconducted at a single testing and were completed together at this point in the testing session.

Emotionally salient task (Part II of emotionally salient task)

This task was done based on a paradigm developed by Dudley et al. (1997a), but modified for the currentstudy to make more personally referent and emotionally salient. The participant was told to imagine that twosurveys of 100 people each were conducted regarding him or her. They were told that in one survey 60 peoplemade positive comments and 40 made negative comments, while in the second survey 60 people made negativecomments and 40 made positive comments about the participant. In a predetermined order, comments fromtheir self-generated list (see ‘‘Emotionally salient task word generation [Part I of emotionally salient task]’’)were stated to the participant, one at a time. Participants engaged in four trials of this task; the order of wordsvaried for each trial. For one of the trials, the survey began with the negative word the participant reportedwas most like him/her and for one of the trials the survey began with the positive word the participant ratedmost like him/her. The participant was asked to determine which survey (the mostly positive or the mostlynegative) was being referenced. As in the neutral task, after each comment was given, the participant wasasked if he or she wanted to be given more comments before deciding or if he or she wanted to decide whichsurvey the comments were drawn from. In addition, once the participant decided, the experimenter requestedthe participant report his or her level of confidence in the decision made on a 1–100 scale. The survey commentsequences were the same as the beads task in that for each pink bead a positive survey comment wassubstituted and for each blue bead a negative word was substituted. The words were also ordered in terms ofhow much on a 1–100 scale the participant rated each word described him/her. The positive word rated by theparticipant as most like him/her was labeled P1 while the positive word of the words selected rated as least likehim/her was labeled P10. Other positive words were ordered based on the participant’s ratings and werelabeled P2–P9. Similarly, the negative word rated by the participant as most like him/her was labeled N1 whilethe negative word of the words selected rated as least like him/her was labeled N10. Other negative words wereordered based on the participant’s ratings and were labeled N2–N9. The survey comment sequences were asfollows:

Sequence A: N1 P1 N2 P2 P3 N3 P4 P5 N4 P6 P7 P8 P9 N5 P10 P1 N6 N7 P2 P3Sequence B: P10 N10 P9 N9 P8 P7 N8 N7 N6 N5 N4 P6 P5 N3 N2 P4 N1 P3 P2 P1Sequence C: P1 N1 N2 N3 P2 N4 N5 N6 N7 N8 P3 N9 N10 P4 P5 P6 P7 N1 N2 N3Sequence D: P10 N10 N9 N8 N7 N6 P9 N5 P8 P7 N4 P6 P5 N3 N2 N1 P4 P3 N10 N9

As with the beads task, participants were assigned to receive one of four orders: (1) A, B, C, D; (2) C, D, A,B; (3) B, A, D, C; (4) D, C, B, A. All participants received a different order for the salient task than they didfor the beads task.

Results

Group classification

Following previous research (e.g., Green, Williams, & Davidson, 2001; Laroi & van der Linden, 2005;Linney et al., 1998) high and low delusion prone groups were formed such that those in the healthy samplewhose PDI scores fell above the median for the healthy sample (median ¼ 97.5) were classified as delusionprone and those whose PDI scores fell below the median were classified as not delusion prone. The presentsample had PDI scores that were fairly consistent with those of the normative sample (Peters et al., 1999),though the present sample had slightly higher scores (see Table 2 for details of the PDI scores for the currentsample). While Laroi and van der Linden (2005) excluded from analyses participants who had PDI scores thatfell at the median, no participant in the present study had a PDI score that was equal to the median score. All

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Table 2

Means, standard deviations, medians, and ranges for the components of the PDI and the PDI total score by delusion status classification

for the healthy sample

Mean (SD) Median Range

PDI—number of beliefs endorsed: total healthy sample 11.32 (5.73) 10.00 1–23

Not delusion prone 6.43 (2.37) 6.00 1–10

Delusion prone 16.20 (3.43) 17.00 9–23

PDI—distress scale: total healthy sample 28.82 (18.59) 25.50 2–74

Not delusion prone 13.90 (6.91) 14.00 2–26

Delusion prone 43.73 (13.96) 42.50 25–74

PDI—preoccupation scale: total healthy sample 29.98 (19.12) 25.50 2–87

Not delusion prone 14.83 (5.58) 15.00 2–24

Delusion prone 45.13 (15.42) 42.00 27–87

PDI—conviction scale: total healthy sample 36.30 (20.00) 34.50 5–88

Not delusion prone 20.03 (7.91) 18.00 5–36

Delusion prone 52.57 (14.27) 52.50 26–88

PDI—total score: total healthy sample 106.42 (61.30) 97.50 12–269

Not delusion prone 55.20 (20.40) 56.50 12–95

Delusion prone 157.63 (42.46) 158.00 100–269

Note: N ¼ 60; n ¼ 30 not delusion prone and n ¼ 30 delusion prone.

D.M. Warman et al. / Behaviour Research and Therapy 45 (2007) 1255–1269 1261

participants in the clinical sample were classified as having active delusions, as each had a PANSS score of atleast 3 for the delusions item.

Preliminary analyses

As shown in Table 1, there were significant differences between the delusion status groups on demographicvariables (i.e., gender, race, age). Further examination of these demographic variables, however, suggests thatrace and gender differences are an artifact of the university vs. clinical sample distinction (all w2 analysesbetween delusion prone and non-delusion prone individuals, p4.06; all w2 analyses between clinical anduniversity participants, po.001). Similarly, the vast majority of variation in age between delusion statusgroups was an artifact of the university vs. clinical distinction; participants from the clinical sample weresignificantly older (M ¼ 48.08, SD ¼ 6.03) than participants from the university sample (M ¼ 21.35,SD ¼ 5.53; t (95) ¼ 22.34, po.001). These findings are unsurprising given the samples being studied. Becausethese demographic variables are redundant with delusion status, they will not be considered as mitigatingfactors in further analyses.

To determine whether participants’ levels of depressive and anxious symptomology (as measured by theBDI-II and BAI, respectively) were related to delusion status classification, one way ANOVAs were used withfirst BDI and then BAI as dependent variables and delusion status as the independent variable. BDI score wassignificantly related to delusion status, F (2, 94) ¼ 7.11, p ¼ .001. Post-hoc Tamhane’s tests indicated thatindividuals who were not delusion prone (M ¼ 8.73, SD ¼ 6.24) endorsed significantly fewer depressionsymptoms than either those who were delusion prone (M ¼ 14.37, SD ¼ 9.49) or those with delusions(M ¼ 17.92, SD ¼ 12.40). Participants who were delusion prone and those with delusions did not differ fromeach other in terms of depressive symptoms. Further, BAI score was significantly related to delusion status, F

(2, 94) ¼ 4.77, p ¼ .011. Post-hoc Least Significant Difference tests indicated that individuals withschizophrenia endorsed significantly more anxiety symptoms (M ¼ 17.54, SD ¼ 12.88) than those who werenot delusion prone (M ¼ 9.80, SD ¼ 7.93). Those who were delusion prone (M ¼ 14.83, SD ¼ 8.53) did notdiffer from either the schizophrenia or not delusion prone groups.

To determine if BDI and BAI scores affected scores on the dependent variables, a series of bivariatecorrelational analyses was conducted. In terms of BDI, no relationships were found in terms of average

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number of beads requested, average number of survey comments requested, confidence on the beads task, andconfidence on the survey task (all p’s4.42). There was a significant relationship between BDI score andaccuracy (defined as the percentage of trials where participants made the correct choice of bead jar or survey)for both beads (r ¼ �.25, p ¼ .014) and surveys (r ¼ �.29, p ¼ .004). Individuals reporting lower levels ofdepressive symptomology were significantly more accurate in their outcome judgments for both salient andnon-salient tasks than participants who reported higher levels of depressive symptomology. Therefore, whenexamining accuracy for both the beads tasks and the survey tasks, BDI was entered as a covariate. For allother dependent variables, BDI was not entered as a covariate. In terms of BAI, no differences were found interms of any of the dependent variables (all p’s4.07). Thus, BAI was not entered as a covariate in any analysesand will not be considered further.

Primary analyses

Jumping to conclusions

To determine the impact of delusion status classification and neutral versus salient stimuli on the number ofstimuli participants requested, a 2 (Type of Stimuli: Neutral versus Salient) � 3 (Delusion StatusClassification: Active Delusions versus Delusion Prone versus Not Delusion Prone) mixed model ANOVAwas conducted with type of stimuli as the within-subjects variable, delusion status classification as thebetween-subjects variable, and average number of beads/survey comments requested as the dependentvariables. No main effect emerged for Type of Stimuli, F (1, 91) ¼ .33, p ¼ .57, Z2 ¼ .004, indicating thatparticipants requested the same number of stimuli for the neutral and the salient tasks. Further, there was nointeraction between Type of Stimuli presented and Delusion Status Classification, F (2, 91) ¼ 1.26, p ¼ .29,Z2 ¼ .03. There was, however, a significant main effect for Delusion Status, F (2, 91) ¼ 33.83, po.001,Z2 ¼ .43. Follow up tests (based on estimated marginal means) indicated that those with delusions requestedsignificantly fewer stimuli (M ¼ 1.72, SE ¼ .34) than either the delusion prone (M ¼ 5.53, SE ¼ .37) or thenot delusion prone groups (M ¼ 4.83, SE ¼ .37), who did not differ from one another (see Fig. 1).

Confidence

To determine the impact of delusion status and neutral versus salient stimuli on participants’ confidence, a 2(Type of Stimuli: Neutral versus Salient) � 3 (Delusion Status Classification: Active Delusions versusDelusion Prone versus Not Delusion Prone) mixed model ANOVA was conducted with type of stimuli as thewithin-subjects variable, delusion status classification as the between-subjects variable, and average level ofconfidence reported (on a scale of 1–100) on beads/salient tasks as the dependent variables. A significant maineffect emerged for Type of Stimuli presented (F (1, 92) ¼ 22.76, po.001, Z2 ¼ .20), which was moderated by aType of Stimuli � Delusion Status Classification interaction, F (2, 92) ¼ 3.83, p ¼ .02, Z2 ¼ .08. Follow upanalyses indicated that those who had delusions and those who were delusion prone were significantly moreconfident on the salient task than they were on the beads task, F (1, 34) ¼ 14.46, p ¼ .001, Z2 ¼ .30 (M forsalient task ¼ 75.46, SD ¼ 19.91, M for beads task ¼ 56.51, SD ¼ 25.21) and F (1, 29) ¼ 8.39, p ¼ .006,Z2 ¼ .23 (M for salient task ¼ 62.98, SD ¼ 18.67, M for beads task ¼ 54.00, SD ¼ 21.03) , respectively. Thosewho were not delusion prone reported an equivalent degree of confidence on salient and beads tasks, F (1,29) ¼ 2.45, p ¼ .13, Z2 ¼ .08 (M for salient task ¼ 59.13, SD ¼ 19.09, M for beads task ¼ 54.83, SD ¼ 22.23).Further, on the salient task (F (2, 93) ¼ 6.89, p ¼ .002, Z2 ¼ .13), those with delusions were significantly moreconfident in their performance (M ¼ 75.74, SD ¼ 19.69) than were those who were delusion prone(M ¼ 62.98, SD ¼ 18.67) and those who were not delusion prone (M ¼ 59.13, SD ¼ 19.09), who did notdiffer from one another. Delusion status did not affect participants’ confidence on the neutral task, F (2,92) ¼ .10, p ¼ .90, Z2o.01. Fig. 2 depicts these results.

Accuracy

To determine the impact of delusion status classification and neutral versus salient stimuli on participants’accuracy, a 2 (Type of Stimuli: Neutral versus Salient) � 3 (Delusion Status Classification: Active Delusionsversus Delusion Prone versus Not Delusion Prone) mixed model ANOVA was conducted with type of stimulias the within-subjects variable, delusion status as the between-subjects variable, percentage of beads/salient

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Delusion Status

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Self -Referent Task

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Fig. 2. Average confidence in decision made for neutral and salient self-referent tasks as a function of delusion status (active delusions,

delusion prone, or not delusion prone).

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Delusions Delusion Prone Not Delusion Prone

Beads Task

Fig. 1. Average number of stimuli requested (beads for neutral task, survey comments for salient self-referent task) as a function of

delusion status (active delusions, delusion prone, or not delusion prone).

D.M. Warman et al. / Behaviour Research and Therapy 45 (2007) 1255–1269 1263

ARTICLE IN PRESS

0

10

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30

40

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60

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90

Delusion Status

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Fig. 3. Percentage of decisions made that were accurate for neutral and salient self-referent tasks as a function of delusion status (active

delusions, delusion prone, or not delusion prone).

D.M. Warman et al. / Behaviour Research and Therapy 45 (2007) 1255–12691264

trials (0–100%) the individual got correct as the dependent variables, and BDI score entered as a covariate. Asignificant main effect emerged for Delusion Status (F (2, 90) ¼ 27.06, po.001, Z2 ¼ .38), which wasmoderated by a Type of Stimuli � Delusion Status Classification interaction, F (2, 90) ¼ 3.57, p ¼ .03,Z2 ¼ .07. Follow up tests revealed that those who had delusions were significantly less accurate on the salienttask than they were on the beads task, F (1, 32) ¼ 5.40, p ¼ .03, Z2 ¼ .14 (M for salient task ¼ 40.44,SE ¼ 4.24, M for beads task ¼ 53.68, SE ¼ 4.75). Those who were delusion prone and those who were notdelusion prone demonstrated a comparable degree of accuracy on salient and beads tasks, F (1, 28) ¼ 1.67,p ¼ .21, Z2 ¼ .06 (M for salient task ¼ 84.17, SE ¼ 3.54, M for beads task ¼ 78.33, SE ¼ 3.53) and F (1,28) ¼ .03, p ¼ .87, Z2 ¼ .001 (M for salient task ¼ 77.50, SE ¼ 3.27, M for beads task ¼ 76.67, SE ¼ 4.78),respectively. Further, on the beads task (F (2, 90) ¼ 7.36, p ¼ .001, Z2 ¼ .14), those with delusions weresignificantly less accurate (M ¼ 55.31, SE ¼ 4.44) than those who were delusion prone (M ¼ 78.35,SE ¼ 4.52) and those who were not delusion prone (M ¼ 74.80, SE ¼ 4.75), who did not differ from oneanother. Likewise, on the salient task, (F (2, 91) ¼ 35.37, po.001, Z2 ¼ .44), those with delusions weresignificantly less accurate (M ¼ 41.31, SE ¼ 3.70) than those who were delusion prone (M ¼ 84.23,SE ¼ 3.85) and those who were not delusion prone (M ¼ 75.91, SE ¼ 4.04), who did not differ from oneanother. Interestingly, as there were only two choices, those with delusions scored even below chance levels onthe salient task. Fig. 3 depicts these results.

Supplemental analyses

Effect of valence of first word in salient task

Warman and Martin (in press) found that valence of stimuli (positive versus negative) was related tojumping to conclusions, such that negative stimuli led to decreased data gathering for those high in delusionproneness. For the present study, one of the salient trials began with the negative self-generated word theparticipant labeled as the most like him/her and one of the salient trials began with the positive self-generatedword the participant labeled as the most like him/her. The following analyses were conducted to determine theimpact of valence on performance during the salient task.

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Jumping to conclusions. To determine whether valence of stimuli was related to jumping to conclusions a 2(Valence of Stimuli: Positive or Negative) � 3 (Delusion Status Classification: Active Delusions versusDelusion Prone versus Not Delusion Prone) mixed model ANOVA was conducted, with valence of stimuli asthe within-subjects variable and average number of survey comments requested as the dependent variable.There were significant main effects for Valence of Stimuli, F (1, 92) ¼ 10.41, p ¼ .002, Z2 ¼ .10, and forDelusion Status Classification, F (2, 92) ¼ 32.59, po.001, Z2 ¼ .42; their interaction was not significant F (2,92) ¼ 1.15, p ¼ .32, Z2 ¼ .02. Participants requested more stimuli in the self-referent trial that began with thenegative word (M ¼ 4.28, SD ¼ 3.31) than the self-referent trial that began with the positive word (M ¼ 3.63,SD ¼ 2.49). Individuals with delusions requested fewer words than those who were delusion prone and thosewho were not delusion prone, who did not differ from each other; this finding was detailed in a previoussection of these results.

Confidence. To determine whether valence of stimuli was related to confidence on tasks, a 2 (Valence ofStimuli: Positive or Negative) � 3 (Delusion Status Classification: Active Delusions versus Delusion Proneversus Not Delusion Prone) mixed model ANOVA was conducted with valence of stimuli as the withinsubjects variable and confidence reported as the dependent variable. There was no significant main effect forValence of Stimuli, F (1, 92) ¼ .94, p ¼ .33, Z2 ¼ .01, although there was a significant main effect for DelusionStatus Classification, F (2, 92) ¼ 9.35, po.001, Z2 ¼ .17. No significant interaction emerged, F (2, 92) ¼ .77,p ¼ .47, Z2 ¼ .02. Thus, individuals were equally confident regardless of whether the salient trial began with aself-referent positive or self-referent negative word. Individuals with delusions were more confident on thesetasks than those who were delusion prone and those who were not delusion prone, who did not differ fromeach other; this finding was detailed in a previous section of these results.

Requesting only one or two stimuli

A number of studies have examined the jumping to conclusions reasoning bias by defining this bias asrequesting only one (Moritz & Woodward, 2005; Van Dael et al., in press) or two or fewer items (Garety et al.,2005) on reasoning tasks. Such studies have demonstrated that those with delusions jump to conclusions athigh rates; based on this rigid criteria, approximately 50% of those with delusions jumped to conclusions inprevious studies. When defined as requesting an average of only one bead across the four trials in the presentstudy, 54% of those with delusions jumped to conclusions, relative to 0% of delusion prone individuals and7% of individuals who were not delusion prone. On salient tasks, when defined as requesting an average ofonly one survey comment across the four trials, 46% of those with delusions jumped to conclusions, relative to3% of delusion prone individuals and 10% of individuals who were not delusion prone. When defined asrequesting an average of two or fewer beads across the four trials, 80% of those with delusions jumped toconclusions, compared to 7% of individuals who were delusion prone and 23% of those who were notdelusion prone. When defined as requesting an average of two or fewer survey comments across the four trials,86% of those with delusions jumped to conclusions, compared to 3% of those who were delusion prone and20% of those who were not delusion prone. It is clear from the above that jumping to conclusions, whendefined in this manner, happened at an extremely high rate for those with delusions and that jumping toconclusions was nearly absent by delusion prone individuals.

Discussion

The present study was an investigation into the jumping to conclusions reasoning bias of those withdelusions, those who were delusion prone, and those who were not delusion prone. Probabilistic reasoningtasks were employed, both neutral and highly personally referent. The main findings indicate that, consistentwith previous research, those with delusions demonstrate substantial jumping to conclusions. In addition,those with delusions are significantly more confident than delusion prone and not delusion prone individualsin their decisions on tasks that are self-referent, despite their hasty decisions and limited data to support theirdecisions. Finally, those with delusions were overwhelmingly inaccurate in the decisions they made, perhapsnot unexpected considering their limited information gathering. Those who were delusion prone did notdemonstrate the majority of reasoning biases that those with delusions displayed, yet delusion prone

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individuals were more confident in their decisions when information was emotionally salient than wheninformation was emotionally neutral.

The beads task, which was utilized in the current study, is a popular method to investigate reasoning andjumping to conclusions for neutral stimuli (Garety et al., 1991; Huq et al., 1988; Moritz & Woodward, 2005).Previous research has demonstrated that individuals with delusions jump to conclusions and that this findingis robust when participants are permitted to determine how much information they gather before making adecision. The present study supported previous findings that jumping to conclusions is evident in those withdelusions. Dudley et al. (1997b) and Garety et al. (2005) found that those with delusions were less likely tojump to conclusions when the task was difficult, such as making decisions about jar origin with a 60:40 ratio,than when the task was easy, such as an 85:15 ratio. While no 85:15 ratio was used in the current study,considering 80% of those with delusions requested two or fewer beads (a definition which has been used inprevious studies, e.g., Garety et al., 2005) it is difficult to imagine that an easier task would have resulted inmore jumping to conclusions. Moritz and Woodward (2005) suggested that when individuals make errors thatare illogical, such as making a decision after only one bead and saying the jar of origin is the one with morebeads of the other color, it is probable they misunderstood the task. Given the high rate of requesting only 1bead for those with delusions in the present study and the very high rates of errors for those with delusions, alack of comprehension of the task is a possible explanation for the present results. The present study reinforcesMoritz and Woodward’s conclusion that it may be imperative to include ways of determining whetherparticipants understand the task, such as requesting they discuss why they made certain decisions or havingthem outline the instructions for the task after they are told what they are.1

In addition to the beads task, a second probabilistic reasoning task was employed, one that built on Dudleyet al.’s (1997a) procedure that consisted of drawing predetermined survey comments from one of two surveys,one mainly positive and the other mainly negative, that was conducted about a person very much like theparticipant. It is likely that that the self-referent nature of Dudley et al.’s task was emotionally arousing, inthat participants with delusions and control groups requested less information on this task than they did on anemotionally neutral task. To increase the self-reference, and perhaps emotional arousal, in the current study,participants were requested to generate their own descriptions of themselves, both positive and negative; thosewords were then read to them as the survey comments and the participant could request as many words as he/she desired before deciding which survey was being referenced. In this task, as was found for the beads task,those with delusions requested significantly less information than those who were delusion prone and thosewho were not delusion prone. Unlike the beads task, for which all participant groups reported equivalentconfidence, those with delusions reported significantly more confidence in their decisions on the salient taskthan did the other participants. As delusions are expected to consist of emotionally salient, not emotionallyneutral material, this finding is quite relevant to understanding how those with delusions reason aboutpersonally referent material. It has been argued that those with delusions demonstrate an egocentric bias (Beck& Rector, 2002); perhaps this bias, coupled with significant confidence in decisions made on extremely limitedinformation, helps explain the persistence of delusions.

It is especially concerning that individuals with delusions were so confident in their decisions on salient tasksconsidering how little information they gathered before making their decision. While those with delusionswere inaccurate on both the neutral and the salient tasks, they were particularly inaccurate in decisions on thesalient task. Thus, on salient tasks they had heightened confidence and heightened inaccuracy. It appears

1Another possibility for the high rate of jumping to conclusions for those with delusions in the present study and, subsequently, their

high rate of errors may have been due to the number of trials of tasks used in the present study. Unlike a number of previous studies (e.g.,

Garety et al., 2005) the present study included four trials of tasks, as opposed to only one. It is possible individuals requested fewer stimuli

over the course of the four trials, perhaps due to fatigue, boredom, or giving up. To determine the potential effects of repeated trials,

Menon, Pomarol-Clotet, McKenna, & McCarthy (2006) examined jumping to conclusions both as means over four trials and also only for

the first trial of tasks. Following their procedure, we conducted analyses on the number of stimuli requested for only the first trial of the

beads task and the salient task. Means were similar and significant differences were identical to those reported across the four trials.

Furthermore, it does not appear that individuals with delusions were likely to put less effort into tasks as trials continued; 89% of those

with delusions requested two or fewer stimuli on their first trial of the beads task and 91.4% requested two or fewer stimuli on their first

trial of the survey task, numbers that are strikingly similar to their average number collected (detailed in Results). Thus it appears that

poor performance overall did not appear to be due to the effect of repeated trials.

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possible that the emotion evoked by the highly self-referent task resulted in very poor judgment and decisionmaking ability. It has been argued that overconfidence in errors may be an important element inunderstanding delusions (Moritz, Woodward, Whitman, & Cuttler, 2005). The present findings demonstratethat accuracy may be particularly impaired when material is emotionally arousing and that individuals may beless likely to question judgments under such conditions due to heightened confidence in decisions.

Dudley et al. (1997a) found that individuals requested less information when stimuli were personallyreferent than when stimuli were emotionally neutral. The present study did not replicate this finding. In termsof those who had delusions, this was likely due to a floor effect; the vast majority of individuals with delusionsrequested two or fewer beads during the neutral task. Clearly there was little room for individuals to requestless information. In terms of delusion prone versus not delusion prone, participants requested approximatelythe same number of beads as they did survey comments. Interestingly, while participants requested the samenumber of stimuli for the different tasks, how they evaluated their judgment varied. Those with delusions andthose who were delusion prone were significantly more confident in their decisions on the self-referent taskthan they were on the beads task. A recent investigation demonstrated that those who were delusion pronereported more confidence in their own judgment than those who were not delusion prone (Warman & Martin,2006). The present investigation lends further support to the notion that confidence in judgment may be acritical factor in understanding individuals lower on the continuum of delusional ideation and that delusionprone individuals process self-referent material differently than do individuals who are not delusion prone(Warman & Martin, in press).

The present study did not replicate previous findings that those who are delusion prone have a jumping toconclusions bias similar to that found by individuals with delusions. In fact, when jumping to conclusions wasdefined as requesting an average of only one stimulus, jumping to conclusions was nearly absent for delusionprone individuals. Interestingly, if using this definition, a slightly greater percentage of individuals who werenot delusion prone jumped to conclusions, a difference that becomes quite pronounced when the definition ofrequesting an average of two or fewer stimuli is used. Colbert and Peters (2002), using the beads procedure,found that those who scored high on the Peters et al. Delusions Inventory requested fewer beads beforemaking a decision than those who scored low on the measure. Warman and Martin (in press) did not replicatetheir finding on neutral tasks, but did find that those who were high in delusion proneness requested lessinformation before making a decision than those low in delusion proneness when stimuli were emotionallysalient, using the procedure developed by Dudley et al. (1997a). Perhaps the reason no differences betweendelusion prone and not delusion prone participants were found in the current study is that the presentinvestigation, unlike the previous investigations (Colbert & Peters, 2002; Warman & Martin, in press), used arelatively difficult reasoning task. Individuals request more information when tasks are difficult, a finding thatextends to those who have delusions (Dudley et al., 1997b). Perhaps those who are delusion pronesubstantially adjust their information gathering strategies on difficult tasks and this adjustment results in theirnot jumping to conclusions. Of note, a recent study demonstrated that those who are delusion prone recognizethe possibility of being mistaken even more than individuals who are not delusion prone (Warman & Martin,2006). Garety et al. (2005) found that individuals with delusions who reported a possibility of being mistakenabout their beliefs were less likely to jump to conclusions than those who did not recognize this possibility. Asthose who are delusion prone appear to have a high recognition of being mistaken, it is possible thisrecognition alters behavior on difficult tasks such that there is an absence of jumping to conclusions.

All participants, regardless of delusion status, requested more information during the emotionally salienttask that began with the most self-referent negative word than the emotionally salient task that began with themost self-referent positive word. Previous investigations have not examined this question directly withindividuals with active delusions, thus no a priori hypotheses could be made regarding this population. Arecent investigation using a minimally self-referent task, however, demonstrated that those who were high indelusion proneness were more likely to jump to conclusions when the first word was negatively valenced, afinding in direct opposition to the current findings (Warman &Martin, in press). Perhaps this finding is relatedto the degree of self-reference for the two tasks. In the original investigation, individuals were told surveyswere conducted about a person who was like the participant; in the current task, individuals were told thesurvey was about them directly, and words they used to describe themselves were used. This task can beconsidered far more self-referent than what was used in previous studies. Perhaps this self-reference motivated

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participants to request more information when the stimuli was negative, to provide some possibility that theselected survey was not the negative one.

The present study demonstrated that those with delusions jump to conclusions on both neutral and salient,self-referent tasks. Those who were delusion prone and those who were not delusion prone did not differ fromone another in terms of information gathering on either task. Those who were delusion prone, however, weremore confident in their decisions on emotionally salient tasks than they were on emotionally neutral tasks,demonstrating that self-reference affects how those who are delusion prone process information. The presentstudy was the first to examine the continuum of psychosis and how it relates to probabilistic reasoning ondifficult neutral and salient tasks. While categorizing participants into high versus low delusion pronenessgroups is consistent with previous research (e.g., Colbert & Peters, 2002; Green et al., 2001; Laroi & van derLinden, 2005; Linney et al., 1998), such a procedure presents possible limitations. As the point of interest is toexamine delusional ideation on a continuum (Peters et al., 1999), it is a bit contradictory to divide individualsinto categorically defined groups (Laroi & van der Linden, 2005). Further, while studying university studentsis a common way to examine delusion proneness (e.g., Green et al., 2001; Laroi & van der Linden, 2005;Linney et al., 1998), it is unlikely that doing so truly captures the continuum of delusional ideation. Two recentreasoning studies examined delusional ideation in non-clinical samples in a manner more likely to assess thehigher end of delusional ideation in the normal population—Van Dael et al. (in press) included healthy (i.e.,no history of psychotic disorder) relatives of individuals with a history of psychotic disorder, and Colbert andPeters (2002) recruited a number of participants from Spiritualist churches, a group previously shown to scorehigher on the PDI. Perhaps had such recruitment been done for the present study, differences in reasoningbetween delusion prone and not delusion prone individuals would have emerged. It is possible that highly self-referent tasks would affect those considerably higher in delusion proneness differently than did such tasks forthose classified as delusion prone in the current sample. Such a possibility awaits empirical investigation.

Acknowledgments

The authors would like to thank Dr. Aaron T. Beck for his assistance in the facilitation and preparation ofthis research.

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