Cheng 2012

6 pages
12 views

Please download to get full document.

View again

of 6
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Share
Description
game
Tags
Transcript
  Schizophrenia and risk-taking: Impaired reward but preservedpunishment processing Gordon L.F. Cheng  a,b , Joey C.Y. Tang  a,c , Frendi W.S. Li  d , Esther Y.Y. Lau  a,d , Tatia M.C. Lee  a,b,d,e, ⁎ a Laboratory of Neuropsychology, The University of Hong Kong, Hong Kong, China b Laboratory of Cognitive Affective Neuroscience, The University of Hong Kong, Hong Kong, China c Number Laboratory, The University of Hong Kong, Hong Kong, China d Department of Psychology, The University of Hong Kong, Hong Kong, China e The State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong, China a b s t r a c ta r t i c l e i n f o  Article history: Received 17 September 2011Received in revised form 14 December 2011Accepted 4 January 2012Available online 27 January 2012 Keywords: Balloon Analogue Risk TaskRisky-Gains TaskPsychosisFrontostriatal system Risky decision-making is subserved by the frontostriatal system, which includes a network of interconnectedbrain regions known to be dysfunctional in patients with schizophrenia. This study aimed to investigatewhether and to what extent patients with schizophrenia display a different pattern of risk-taking behaviorrelative to matched healthy controls. The Balloon Analogue Risk Task (BART) and the Risky-Gains Taskwere used as naturalistic measures of risk-taking behavior in 25 patients with schizophrenia and 25 controls.Results oftheBARTrevealedthatpatientsbehavedmoreconservatively,andthisinturnledtosuboptimalriskydecision-making. Consistently, patients behaved more conservatively in the Risky-Gains Task. Interestingly,however, they adjusted the pattern of risk-taking following a punished trial similar to controls. These  󿬁 ndingsindicatethatpatientshaveimpairedrewardbutpreservedpunishmentprocessing.Thisstudycomplementspre-vious studies on decision-making in schizophrenia and suggests speci 󿬁 c rather than widespread abnormalitiesalong the frontostriatal system in schizophrenia.© 2012 Elsevier B.V. All rights reserved. 1. Introduction Schizophrenia is a form of psychopathology that implicates abnor-mal functioning in the frontostriatal system (e.g. Abi-Dargham, 2003;Kimetal.,2003;seeBarchandDowd,2010).Oneofthehighercognitive processes that are known to involve the frontostriatal system is riskydecision-making, which is a form of behavior that entails striking abalance between options with different likelihoods of reward andpunishment. Processing of reward and punishment is subserved byinterconnected brain regions including the prefrontal cortex (PFC),anterior cingulate cortex (ACC), insula, and subcortical areas such asthe striatum (e.g. Knutson et al., 2000; O'Doherty et al., 2001; Elliott etal., 2003; FitzGerald et al., 2009).Owing to the signi 󿬁 cance of the frontostriatal system in riskydecision-making, the present study aimed to investigate the perfor-mance of patients with schizophrenia on naturalistic risk-taking tasksthat are known to involve this brain system. These risk-taking tasksinclude the Balloon Analogue Risk Task (BART; Lejuez et al., 2002) andRisky-Gains Task (Paulus et al., 2003), both known to involve brainregions along the frontostriatal system in response to choosing a riskyover a safe option (Paulus et al., 2003; Lee et al., 2008a, 2008b; Rao etal., 2008; Lee et al., 2009). Several studies have examined the extentof suboptimal decision-making in patients with schizophrenia usingthe Iowa Gambling Task (IGT), which was srcinally believed to relyon the ventromedial PFC (Bechara et al., 1994, 2000) and now knownto involve the frontostriatal network (Li et al., 2010). These studieseither reported no difference in IGT performance between patientswith schizophrenia and healthy controls (e.g. Wilder et al., 1998;Cavallaro et al., 2003; Evans et al., 2005; Rodríguez-Sánchez et al.,2005;Turnbulletal.,2006)orthatpatientsselectedmoredisadvantagedoptions which led to lower returns (Ritter et al., 2004; Shurman et al.,2005; Kester et al., 2006; Sevy et al., 2007; Yip et al., 2009). Despite thecon 󿬂 icting  󿬁 ndings, these studies provided important insight that atleast in some patients with schizophrenia, there seems to be dif  󿬁 cultyin making optimal decisions. Employing the BART and Risky-GainsTask in patients with schizophrenia will add to our knowledge of thespeci 󿬁 c characteristicsof risk-taking behavior in this clinical populationasthedesignsofsuchtasksallowforadirectassessmentofthetendencyto engage in risky versus conservative options. This knowledge cansupplement existing  󿬁 ndings from IGT studies, some of which indicatea very different pattern of risky decision-making between patientswith schizophrenia and the healthy population. To our knowledge thisis the  󿬁 rst reported study that investigated schizophrenia using theBARTandRisky-Gainstasks.Wechosethesewell-establishedcomputer-ized tasks as risk-taking measures for reasons of ecological validity.The Risky-Gains Task and BART are with and without time pressure Schizophrenia Research 136 (2012) 122 – 127 ⁎  Corresponding author at: K610, The University of Hong Kong, Pokfulam Road,Hong Kong, China. Tel.: +852 2857 8394; fax: +852 2819 0978. E-mail address:  tmclee@hku.hk (T.M.C. Lee).0920-9964/$  –  see front matter © 2012 Elsevier B.V. All rights reserved.doi:10.1016/j.schres.2012.01.002 Contents lists available at SciVerse ScienceDirect Schizophrenia Research  journal homepage: www.elsevier.com/locate/schres  respectively.Therefore,usingbothtasksmaximizestheabilitytogener-alize  󿬁 ndings to real life situations where risky decision-making can bemade in both contexts of deliberation and haste.Our prediction was formulated based on a recent report thatpatients with schizophrenia have a preserved capacity to processimmediaterewardbutareunabletoutilizethisinformationinmakinglong-term decisions (Heerey et al., 2008). This behavioral temporalmyopia is reminiscent of   󿬁 ndings from some previous studies thatinvestigated schizophrenia using the IGT. Patients tended to selectcards from more disadvantaged decks that contained large rewardbut at times even larger penalties, which led to lower returns in thelong run (Ritter et al., 2004; Shurman et al., 2005; Kester et al., 2006;Sevy et al., 2007; Yip et al., 2009). Both the BART and Risky-Gainstasks require making risky decisions over a time window, i.e. risk-taking is measured as a tendency to withhold until larger rewardsare presented. Based on such a temporally accumulated design, itwas hypothesized that patients with schizophrenia would fail toutilize reward information to guide long-term decision-making, andthis would manifest as lower scores in the BART and different ratesof choosing safe and/or risky options relative to controls in theRisky-Gains Task. 1 We also aimed to further characterize risk-takingbehavior by investigating: (1) the reaction time for choosing eachoption; and (2) correlations between risk-taking measures andpatients' clinical pro 󿬁 les. 2. Method  2.1. Participants Twenty- 󿬁 ve Chinese patients with schizophrenia (in- and out-patients) were recruited from the Castle Peak Hospital or Tuen MunMental Health Centre, Hong Kong. Diagnoses were made accordingto DSM-IV-TR (APA, 2000). Patients were either receiving typical(n=6) or atypical antipsychotic (n=18) drugs (medication recordfor one patient failed to be retrieved). Twenty- 󿬁 ve Chinese healthycontrol participants were recruited. Exclusion criteria for both thepatient and control groups were history of neurological disorder,substance abuse, head injury with loss of consciousness, and alsohistory of psychiatric disorder for the control group. All participantswere right-handed and each group consisted of 9 males. See Table 1for comparison of demographics between patients and controls, andalso patients' clinical details.This study was approved by the local ethics committee, consentedby all participants, and carried out according to the Declaration of Helsinki.  2.2. Experimental tasks After completion of background measures including IQ (Raven'sProgressive Matrices; Raven, 2008), mood rating (2nd Chineseversion of Beck Depression Inventory; Chinese Behavioral ScienceCorporation, 2000), and in addition for patients the Positive andNegativeSyndromeScale(PANSS;Kayetal.,1987),participantscarriedouttwocomputerizedrisk-takingtasks:theBalloonAnalogueRiskTaskand Risky-Gains Task. Below are brief descriptions of the risk-takingtasks. See Fig. 1 for detailed task procedures.  2.2.1. Balloon Analogue Risk Task (BART) This task simulates the pumping of a balloon, which in 󿬂 ates by asmall degree with each pump. The willingness to in 󿬂 ate balloons isindicative of deliberative risky behavior since each pump leads toeither an extra point gained in the temporary repository or balloonexplosion. Alternatively, participants could decide to collect points,which prevent the balloon from exploding and saving points to apermanent repository. Three dependent measures were derivedfrom BART. First, the adjusted score was calculated by averaging thenumber of pumps for each unexploded balloon. Exploded balloonswere not included since in these trials participants stopped pumpingwithout a choice. The adjusted score serves as a measure of decision-making quality (i.e. a higher score indicates a more optimal decision).Tocomplementtheadjustedscoreasameasureofrisk-taking,analyseswerealsocarriedoutontherateofexplodedballoonsandaveragetimespent on each balloon.  2.2.2. Risky-Gains Task Inthistaskparticipantsdecidedwhethertotakethecurrentsmallerreward, or wait for a larger reward with the potential to lose in a hastycontext. Speci 󿬁 cally, participants were asked to select 20, 40, or 80points with the risk of losing points as they proceeded with their judgments. Selecting 20 was always the safe option that guarantees a(small) reward, while waiting for and selecting 40 or 80 were riskysince it has the potential of either a (larger) reward or punishment.The rates of choosing safe (+20) and risky (+/ − 40, +/ − 80) optionswere calculated as the primary dependent measure of risk-takingbehavior. In order to reveal sensitivity to punishment, we tested therates of choosing either options (safe and risky) following each of thetwo outcomes in the preceding trial (rewarded and punished), inaccordance with Leland and Paulus (2005) and Paulus et al. (2003). Risk-taking was further characterized by investigating reaction times(RTs), i.e. the time used to select an option, which could be either safe(+20) or risky (+40, +80).  2.3. Data analysis Univariate analyses of variance (ANOVAs) were conducted to testfor the effect of   group  (patients, controls) in the three BART measures(adjusted score, explosion rate, and time spent on balloon). For theRisky-Gains Task, a 2×2×2 ANOVA on response rates was conductedwith  group  (patients, controls) as between-subjects factor,  response (safe, risky) and  outcome  (rewarded or punished in the precedingtrial) as within-subjects factors. In addition, RTs were investigatedusing a 2×2 ANOVA with  group  and  response  as between-subjectsand within-subjects factors, respectively. Follow-up  t  -tests wereconducted when there was a signi 󿬁 cant interaction between factors.In order to investigate whether different pro 󿬁 les of schizophreniahave an effect on risk-taking behavior, correlation analyses on all of the risk-taking measures with PANSS scores and illness duration 1 Final scores in the Risky-Gains Task were not investigated since this task wasdesigned such that there is no inherent advantage in choosing the safe option overrisky options, and vice versa.  Table 1 Background scores for patient and control groups.Patients(N=25)Controls(N=25)StatisticsMean (SD) Mean (SD)  t p Age 38.2 (7.5) 41.0 (9.0) 1.21  ns Years of education 10.5 (3.2) 11.2 (3.1) 0.81  ns C-BDI-II 10.7 (9.7) 9.4 (8.5)  − 0.53  ns Estimated IQ (RPM) 34.8 (11.5) 50.3 (6.7) 5.83  b .001Age of onset 26.1 (7.9)  – – Duration of illness (years) 12.8 (9.0)  – – No. of admissions 4.0 (5.2)  – – PANSS positive 10.3 (4.0)  – – PANSS negative 12.8 (5.1)  – – PANSS general 21.6 (4.2)  – – Note. C-BDI-II=SecondChineseversionofBeckDepressionInventory(ChineseBehavioralSciences Society, 2000); RPM = Raven's Progressive Matrices (Raven, 2008); PANSS = Positive and Negative Syndrome Scale (Kay et al., 1987); Patients = adults diagnosedwith schizophrenia; Controls = healthy adults matched to patients in terms of age andsex;SD=standarddeviations; t  = t  -valuesfromindependentgroups t  -tests;  p =associ-ated  p -values;  ns  = non-signi 󿬁 cant difference between patients and controls.123 G.L.F. Cheng et al. / Schizophrenia Research 136 (2012) 122 – 127   were conducted. Unless otherwise speci 󿬁 ed, all statistical tests werecarriedoutandreportedwithsigni 󿬁 cancelevel at  p b .05(two-tailed). 3. Results Summary data for both patients and controls are presented inTable 2.  3.1. Group differences in risk-taking behavior  Three dependent measures were derived from the BART: adjustedscore,explosionrate,andtimespentonballoon.Therewasasigni 󿬁 cantgroup effect for the adjusted score [ F  (1,48)=8.77,  p =.005] such thatpatients obtained a lower score than controls. Similarly, the explosionrate was lower in patients relative to controls [ F  (1,48)=4.36,  p b .05].Theseresultsareindicativethatpatientswithschizophreniaperformedthistaskatasuboptimallevel,possiblyduetoanabnormaltendencytoengageinsafeoverriskyactions.Analysisontheaveragetimespentoneach balloon revealed signi 󿬁 cantly longer time in the patient grouprelative to controls [ F  (1,48)=18.1,  p b .001].For the Risky-Gains Task response rates (safe or risky options)were measured as a function of outcome in the preceding trial(rewarded or punished). Analysis revealed no main effects of response [ F  (1,46)=1.45,  p >.05], outcome [ F  (1,46)=1.09,  p >.05],or group [ F  (1,46)=1.09,  p >.05]. The group-by-outcome interactionwas not signi 󿬁 cant [ F  (1,46)=1.09,  p >.05]. There were, however,signi 󿬁 cant group-by-response [ F  (1,46)=4.56,  p b .05] and response-by-outcome [ F  (1,46)=4.25,  p b .05] interactions. Further  t  -testsrevealed that regardless of outcome the control group showed apreference toward choosing risky over safe options [ t  (24)= − 3.17,  p b .01], but for patients there was no difference between rates of choosing risky and safe options [ t  (24)=.98,  p >.05]. This  󿬁 nding is Fig. 1.  Experimental tasks. (A) The Balloon Analogue Risk Task (BART). The BART employed was adapted based on Lejuez et al.'s (2002) srcinal version. For each trial participantshad to decide either to pump the displayed balloon (for one point to the temporary repository) or collect the points accumulated in that trial by pressing the corresponding buttonsonthekeyboard.Eachpump(orpoint)representedrisk-takingbehaviorsincetheballooncouldexplodeateachpumpandconsequentlyallpointsinthetemporaryrepositorywouldbe lost. Deciding to collect the points instead of pumping means that the points are transferred from the temporary repository to the permanent repository (where accumulatedpoints are safe from future balloon explosions). The explosion point of each balloon was between the 1st and 128th pump, set randomly by the computer (this information wasnot known to the participants). Taking the current points (before balloon explosion) and balloon explosion both signi 󿬁 es the end of a trial and beginning of the next. It was madeclear to the participants that there were twenty trials (i.e. twenty balloons). They were simply asked to accumulate as many points as possible in the permanent repository. Atthe bottom of the screen are Chinese translations of: accumulated score, number of pumps, and balloon (already played). (B) Risky-Gains Task. The Chinese version of the srcinaltask(Paulusetal.,2003)wasusedinthisstudyandalsoinsomeofourpreviousexperiments(Leeetal.,2008a,2008b,2009).Participantswere 󿬁 rstshown ‘ 20 ’ onthescreenwiththeoption to take these points by pressing a button, or wait (for 1 s) for the 40 points that follows it. Similarly, when  ‘ 40 ’  was shown they could decide to take 40 points or wait for  ‘ 80 ’ .However,for  ‘ 40 ’ and ‘ 80 ’ therewererisksoflosing thepoints,inwhichcasethenumbers wereshown withaminussignandthecorresponding points(40or80)deductedfrom thetotal score. There were 96 trials: 54 nonpunished (i.e. potential of gaining up to 80 points), 24 punished for  ‘ 40 ’  (i.e. losing 40 points if the safe  ‘ 20 ’  option was not taken), and 18punished for  ‘ 80 ’  (i.e. losing 80 points if both  ‘ 20 ’  and  ‘ 40 ’  were not taken). These trials were constructed so that there was no advantage in choosing the safe over risky option,andviceversa(Paulusetal.,2003).Participantswereaskedtoachieveashighaspossibleontheaccumulatedscore,whichwasdisplayedonthescreenthroughoutthetask.Apracticesession was carried out prior to the proper experiment to ensure accurate understanding of task instructions. Illustrated is a  ‘ punished for 80 ’  trial, in which punishment waspresented if either the  ‘ 20 ’  or  ‘ 40 ’  points were not taken. Top of the screen shows the  ‘ score ’ . Chinese characters for  ‘ you win ’  or  ‘ you lose ’  were shown in accordance to the outcomeof a trial.  Table 2 Means and standard deviations for risk rates (A) and time (B) in both BART and Risky-Gains tasks.A BART Risky-Gains TaskAdjustedscoreExplosionrateRisk rate afterpunishmentRisk rateafter rewardPatients M 27.3 .28 .43 .46(SD) (14.4) (.14) (.31) (.36)Controls M 40.5 .37 .60 .68(SD) (17.1) (.16) (.31) (.27)B BART Risky-Gains TaskTime spent on balloon (s) Safe RT (ms) Risk RT (ms)Patients M 18.4 487 383(SD) (11.7) (95) (90)Controls M 7.50 495 371(SD) (5.26) (116) (84) Note.  BART = Balloon Analogue Risk Task (Lejuez et al., 2002); M = means; SD =standard deviations; s = seconds; ms = milliseconds; RT = reaction time.124  G.L.F. Cheng et al. / Schizophrenia Research 136 (2012) 122 – 127   again suggestive that patients are less willing to take risks relative tocontrols. In addition, regardless of group there were lower rates of risky response [ t  (47)= − 2.09,  p b .05] and higher rates of saferesponse [ t  (47)=2.10,  p b .05] following a punished trial. Interestingly,the 3-way-interaction was not signi 󿬁 cant [ F  (1,46)=.052,  p >.05]. This 󿬁 nding suggests that, similar to controls, patients adjusted risk-takingfollowing a punished trial and is indicative of intact punishmentsensitivity among patients (Leland and Paulus, 2005). In terms of RTs,both the main effects of group [ F  (1,43)=.33,  p >.05] and group-by-response interaction [ F  (1,43)=.039,  p >.05] were not signi 󿬁 cant.However, there was a main effect of response such that selecting riskyoptions was faster than selecting the safe option [ F  (1,43)=42.6,  p b .001], consistent with our previous study that also investigated RTsin the Risky-Gains Task (Lee et al., 2008b).  3.2. Correlations between risk measures and clinical pro  󿬁 les Correlation analyses were conducted on risk-taking measureswithPANSSscoresandillnessdurationofpatientswithschizophreniain order to investigate whether the suboptimal risk-taking observedcould in part be explained by patients' clinical pro 󿬁 les. As evident inTable 3, none of the PANSS scores or illness duration correlated withany of the risk-taking measures. These results are suggestive of ahomogenous pattern of suboptimal risk-taking behavior in patientswith schizophrenia.  3.3. Supplementary analyses: effect of IQ  Since IQ scores between patients and controls were statisticallydifferent(withcontrolshavinghigherscoresasa group),wefolloweda previous procedure (e.g. Morise et al., 2011) of correlating taskperformance with IQ to see if intelligence might have any relationto risk-taking behavior. Analyses revealed that IQ did not correlatewith any of the risk-taking measures for either patients or controls(all  p >.05, uncorrected). This suggests that the group differences inrisk-taking behaviorwerenotdrivenbythedifferenceinIQ,consistentwith previous studies that also reported no correlations betweenrisk-taking and intelligence (Lejuez et al., 2002; Deakin et al., 2004). 4. Discussion Thisstudyaimedtoinvestigaterisk-takingdecisionsinpatientswithschizophreniausingtheBART(Lejuezetal.,2002)andRisky-GainsTask(Paulusetal.,2003).Threemainresultsemerged:(1)patientsbehavedmore conservatively relative to controls, leading to suboptimal riskydecision-making; (2) in the Risky-Gains Task patients adjusted risk-taking similarly to controls following punishment in the precedingtrial, suggesting intact punishment sensitivity; and (3) none of therisk-taking measures correlated with patients' clinical pro 󿬁 les. Sincean ecological sample of patients with schizophrenia was investigated,theirIQscoresweresigni 󿬁 cantlylowerthanthecontrolgroup.Correla-tionanalyses,however,revealedthatIQdidnotrelatetoanyrisk-takingmeasuresinbothpatientsandcontrols,suggestingthatobservedgroupdifferences were not driven by intelligence.The present  󿬁 nding that patients with schizophrenia behavedsuboptimally in risky decision-making is consistent with the a-prioriprediction, based on their inability to utilize reward information inlong-term decision-making (Heerey et al., 2008). Speci 󿬁 cally, our datasuggest that patients with schizophrenia behaved more conservativelyinboth tasks. This could beexplained in termsof the ‘ temporalmyopia ’ (Bechara et al., 1994) that the patients suffer, since both tasks involveincreasingly large reward through a temporally accumulated design.Theinabilitytodelayimmediatebutsmallerrewardsdespiteavailabilityof larger rewards in the future, therefore, manifested as conservativebehavior in both the BART and Risky-Gains tasks. It is however impor-tant to note that conservative decision-making, although detrimentalto the BART as it leads to lower overall scores in this task, may not beharmful in other contexts (Lighthall et al., 2009). There are instancesthat may bene 󿬁 t from conservative behavior or that neither bene 󿬁 tsfrom risky or conservative behavior, such as in the Risky-Gains Task.TheRisky-GainsTaskisthereforelimitinginthatitdoesnottellwhetherconservative risk-taking in patients may be translated as maladaptivebehavior.Thepresent 󿬁 ndingthatpatients withschizophrenia lacktheabilityto delay immediate grati 󿬁 cation is in line with previous studies thatemployed the Iowa Gambling Task (IGT). These studies demonstratedthat patients preferred disadvantaged decks that contain large rewardbut also at times even larger punishment (Ritter et al., 2004; Shurmanet al., 2005; Kester et al., 2006; Sevy et al., 2007; Yip et al., 2009).However, a novel and important  󿬁 nding of the present study is that inthe Risky-Gains Task all participants responded more conservativelyfollowing a punishment than when they were following a reward. Inotherwords,bothpatientsandcontrolsadjustedtheirdecisionsaccord-ingtotheoutcomeoftheprecedingtrial.The 󿬁 ndingthathealthyadultsbehavedmoreconservativelyfollowingpunishmentisnotnew(Pauluset al., 2003; Leland and Paulus, 2005). However, it is intriguing thatpatients with schizophrenia also followed the same response pattern,despite clear indication of their overall deviant risk-taking behaviorrelative to controls. This  󿬁 nding suggests both an intact sensitivity andutilization of punishment information in patients with schizophrenia(Leland and Paulus, 2005). Processing of reward and punishment isreported to subserve separable neural resources among the healthypopulation. For instance, both the striatum (Delgado et al., 2000;Knutson et al., 2001; Yacubian et al., 2006) and OFC (O'Doherty et al., 2001) are differentially involved in reward and punishment. Thepresent 󿬁 ndingthatpatientswithschizophreniaareimpairedinrewardprocessesbutwithpreservedpunishmentprocessesthereforesuggestsspeci 󿬁 c abnormalities along the frontostriatal network in this clinicalpopulation.Whetherthelevelsoffrontostriatalactivationscandifferen-tiatebetweenpatientsandhealthycontrolsinrelationtoriskydecision-making remains to be con 󿬁 rmed in future imaging studies.Although our hypothesis was formed in relation to a previous 󿬁 nding thatpatients with schizophrenia lackthe ability to use rewardinformation to guide long-term decision-making (Heerey et al.,2008), there are two other possible explanations for the patient'sconservative behavior in both the BART and Risky-Gains tasks. First,patients may have a depleted sensitivity to reward, such that theydidnotappreciateadifferencebetweenthesmallerandlargerrewardoptions. The design of this study did not allow exclusion of this possi-bility, but in our opinion this was unlikely the case since Heerey et al.(2008) demonstrated intact reward sensitivity in patients withschizophrenia using a signal detection procedure. Second, patientsmay have a lack of impulse control, which may be related to the  Table 3 Pearson correlation coef  󿬁 cients of risk-taking measures with PANSS and illnessduration.Schizophreniapatients (N=25)PANSSpositive a PANSSnegative a PANSSgeneral a Illnessduration a BART Adjusted score .18 .20 .38  − .08Explosion score  − .18 .20 .11  − .21Time spent on balloon  − .19  − .18  − .38 .08Risky-GainsTaskRisk rate after reward .23 .30 .28 .16Risk rate afterpunishment.21 .18 .21 .26Safe rate after reward  − .21  − .18  − .21  − .16Safe rate afterpunishment − .23  − .30  − .28  − .26Safe RT  − .08 .12 .02 .44Risk RT .17  − .16 .08 .08 Note.  PANSS = Positive and Negative Syndrome Scale (Kay et al., 1987); BART =Balloon Analogue Risk Task (Lejuez et al., 2002); RT = reaction time. a All correlations are non-signi 󿬁 cant at corrected  p b .001 level.125 G.L.F. Cheng et al. / Schizophrenia Research 136 (2012) 122 – 127 
Related Search
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks
SAVE OUR EARTH

We need your sign to support Project to invent "SMART AND CONTROLLABLE REFLECTIVE BALLOONS" to cover the Sun and Save Our Earth.

More details...

Sign Now!

We are very appreciated for your Prompt Action!

x