L7行为决策和ASMS3000决策分析平台

L7行为决策詹文杰（教授/博导）Office:华中科技大学管理学院611室Telmail:wjzhan@学习目标了解阿莱斯悖论了解期望效用(EU)理论的不足掌握前景理论(PT)掌握常用的行为决策效应及其应用7行为决策7.1阿莱斯悖论7.2EU理论的修正7.3前景理论(PT)7.4行为决策的应用7.1阿莱斯悖论

(Allaisparadox)法国经济学家、诺贝尔经济学奖获得者莫里斯·阿莱斯(M.Allais,1952)进行了彩票选择实验。实验中，被试者被要求在两组彩票组合中分别进行选择。第一组赌局：赌局A：100％的机会得到100万元。赌局B：10％的机会得到120万元，89％的机会得到100万元，1％的机会什么也得不到。

第二组赌局：赌局C：11％的机会得到100万元，89％的机会什么也得不到。赌局D：10％的机会得到120万元，90％的机会什么也得不到。

7.1阿莱斯悖论

(Allaisparadox)实验结果1：绝大多数人选择A而不是B。即:1.00U(100)>0.89U(100)+0.01U(0)+0.1U(120)实验结果2：绝大多数人选择D而非C。即:0.89U(0)+0.11U(100)<0.9U(0)+0.1U(120)阿莱斯悖论的推导：在A/B实验中，绝大多数人选择A，则有：

1.00U(100)>0.89U(100)+0.01U(0)+0.1U(120)在C/D实验中，绝大多数人选择D，则有：

0.89U(0)+0.11U(100)<0.9U(0)+0.1U(120)0.11U(100)<0.01U(0)+0.1U(120)

1.00U(100)-0.89U(100)<0.01U(0)+0.1U(120)

1.00U(100)<0.89U(100)+0.01U(0)+0.1U(120)

“阿莱斯悖论”的启示：“阿莱斯悖论”的解释：人们偏好确定性的结果（Certaineffect）

，而厌恶不确定性的结果。（即人的效用函数往往低估一些只具有可能性的结果，而相对高估确定性的结果。）

“阿莱斯悖论”说明了真实的个体决策行为会系统地违反期望效用理论中的期望效用最大化原理，从而动摇了决策科学的理论基石。附：“埃尔斯伯格悖论”

(Ellsbergparadox)埃尔斯伯格（Ellsberg，1961）进行了如下的博彩实验。假设一个缸中有100个球，其中33个球为红色，其余67个为黑色或黄色，你若从中拿出一个球：博彩A：若球为红色，你得到1000元；博彩B：若球为黑色，你得到1000元。然后再考虑下面的博彩：博彩C：如果球不是红色的，你得到1000元；博彩D：如果球不是黑色的，你得到1000元。3367EU准则EU准则：一个决策变量的期望效用，就是它在不同自然状态下的效用值乘上相对应的发生概率之和。

式中：

EU(ai):行动ai的期望效用；U(Oij):行动ai在自然状态θj下的效用；

p(θj

):自然状态θj发生的概率。7.2EU理论的修正VonNeuman和Morgenstern(1944)的期望效用理论(ExpectedUtility,EU)是关于不确定性决策的规范理论。EU理论认为，假如决策者选择风险决策备择方案的过程符合效用公理，那么他一定是选择预期效用值最大的那项备择方案。Savage(1954)提出主观期望效用(SubjectiveExpectedUtility,SEU)最大化理论，认为决策备择方案的选择遵循主观效用最大化原则。如果某个随机变量X以概率pi取值xi(i=1,2,…,n)，而某人在确定地得到xi时的效用为u(xi)。那么，该随机变量给他的效用便是：EU理论的质疑EU理论及SEU理论描述了“理性人”在风险条件下的决策行为。但实际上人并不是纯粹的理性人，决策还受到人的复杂的心理机制的影响。因此，EU理论对人的风险决策的描述性效度一直受到怀疑。例如，EU理论难以解释阿莱斯悖论、Ellsberg悖论等现象；没有考虑现实生活中个体效用的模糊性、主观概率的模糊性；不能解释偏好的不一致性、非传递性、不可代换性、“偏好反转现象”、观察到的保险和赌博行为；现实生活中也有对EU理论中理性选择上的优势原则和无差异原则的违背；实际生活中的决策者对效用函数的估计也违背EU理论的效用函数。EU理论的修正1(1)Karmark(1978)提出主观权重效用(SubjectivelyWeightedUtility，SWU)的概念，用决策权重替代线性概率，这可以解释Allais问题和共同比率效应，但不能解释优势原则的违背；(2)扩展性效用模型（generalizedutilitymodel）。该类模型的特点是针对同结果效应和同比率效应等，放松期望效用函数的线性特征，或对公理化假设进行重新表述，模型将用概率三角形表示的期望效用函数线性特征的无差异曲线，扩展成体现局部线性近似的扇行展开。这些模型没有给出度量效用的原则，但给出了效用函数的许多限定条件。(3)Kahneman和Tversky(1979)引入系统的非传递性和不连续性的概念，以解决优势违背问题，即前景理论；EU理论的修正2(4)“后悔”的概念被引入，以解释共同比率效应和偏好的非传递性；如Loomes和Sudgen（1982）所提出的“后悔模型”引入了一种后悔函数，将效用奠定在个体对过去“不选择”结果的心理体验上（放弃选择后出现不佳结果感到庆幸，放弃选择后出现更佳结果感到后悔），对预期效用函数进行了改写（仍然保持了线性特征）。(5)允许决策权重随得益的等级和迹象变化，这是对SWU的进一步发展。(6)非可加性效用模型(non-additivityutilitymodel)：这类模型主要针对埃尔斯伯格悖论，该模型认为概率在其测量上是不可加的。卡尼曼特沃斯基7.3前景理论

(ProspectTheory,PT)7.3前景理论

(ProspectTheory,PT)EU理论：是一个规范性范式的风险决策模型。PT理论：是一个描述性范式的风险决策模型。与EU理论不同的是，前景理论分别用价值函数v(x)(valuefunction)取代了效用函数U(x)，用决策权函数(decisionweightfunction)π(p)取代了概率p。

7.3前景理论

(ProspectTheory,PT)价值函数v(x)(valuefunction)决策权函数π(p)(decisionweightfunction)7.3前景理论

(ProspectTheory,PT)Kahneman和Tversky（1979）认为，个人风险条件下的决策过程分为两个阶段：第一阶段：编辑阶段。为了评估决策需要，人们通常在第一阶段对事件进行预处理，包括数据的整合、简化，但是不同的整合、简化方法会得到不同的事件及其组合，并导致人的非理性行为和框架依赖效应，即人对同一问题的最后决策的不一致。第二阶段：估值阶段。编辑阶段之后，决策者对期望进行估值并进行选择。被编辑期望的全部价值V，用两个主观量度π和v来表达。π表示与概率p相对应的决策权重，v反映结果的主观价值，分配给每一结果一个量v(x)。而结果的定义与参考点相对应，在价值尺度中以0为参考点。因此，v(x)离开参考点的程度就是收益或损失的大小。确定效应损失规避参照依赖反射效应迷恋小概率事件前景理论PT理论的基本原理PT理论的基本原理在《赌客信条》一书中，作者孙惟微将前景理论归纳为5句话：1、“二鸟在林，不如一鸟在手”，在确定的收益和“赌一把”之间，多数人会选择确定的好处。所谓“见好就收，落袋为安。称之为“确定效应”。2、在确定的损失和“赌一把”之间，做一个抉择，多数人会选择“赌一把”。称之为“反射效应”。3、白捡的100元所带来的快乐，难以抵消丢失100元所带来的痛苦。称之为“损失规避”。4、很多人都买过彩票，虽然赢钱可能微乎其微，你的钱99.99%的可能支持福利事业和体育事业了，可还是有人心存侥幸搏小概率事件。称之为“迷恋小概率事件”。5、多数人对得失的判断往往根据参照点决定，举例来说，在“其他人一年挣6万元你年收入7万元”和“其他人年收入为9万元你一年收入8万”的选择题中，大部分人会选择前者。称之为“参照依赖”。一、确定效果

(certaintyeffect)1）在下面两个博彩间进行选择：博彩A：33%的机会得到2500元，66%的机会得到2400元，1%的机会什么也得不到；博彩B：100%的机会得到2400元。2）考虑下面两个博彩：博彩C：33%的机会得到2500元，67%的机会什么也得不到；博彩D：34%的机会得到2400元，66%的机会什么也得不到。一、确定效果

(certaintyeffect)在A和B中，问卷的结果显示有82%的受访者选择博彩B。根据期望效用理论有：U(A)<U(B)。即：0.33U(2500)+0.66U(2400)<U(2400)→0.33U(2500)<0.34U(2400)在C和D中问卷显示有83%的人选择了博彩C。根据期望效用理论有：U(C)>U(D)。即：0.33U(2500)>0.34U(2400)

产生矛盾的原因是，人们在面临不确定性时的选择表现出一些与传统的效用理论不符的特征，人的效用函数低估一些只具有可能性的结果，而相对高估确定性的结果，称之为确定效果。二、反射效果

(reflectioneffect)1）在下命两个博彩间进行选择：博彩A：肯定赢1000元;博彩B：50%可能性赢得2023元，50%可能性什么也得不到。2）现在考虑下面两个博彩：博彩C：肯定损失1000元;博彩D：50%可能性损失2023元，50%可能性什么也不损失。

二、反射效果

(reflectioneffect)在A和B中，问卷的结果显示有80%的人选择博彩A。这说明人是风险规避的，理由如下：U(A)>U(B)，可得：

U(1000)>0.5U(0)+0.5U(2023)

在C和D中，问卷的结果显示有92%的人选择了博彩D。这说明人是风险偏好的，理由如下：U(C)<U(D)，可得：

U(-1000)<0.5U(0)+0.5U(-2023)当行动结果是受益时，行为人是风险规避者；而当行动结果是损失时，行为人是风险偏好者，这个称为反射效果。人们对损失和获得的敏感程度是不同的，损失的痛苦要远远大于获得的快乐，即“损失规避”(lossaversion)。效用收益010002000-1000-2000损失参考点效应

（referencepoint）这两个实验其实是一样的，只是玩了个文字游戏而已。在第一个实验中(A/B)，隐含的财富参考点是0。博彩A：肯定赢1000元;博彩B：50%可能性赢得2023元，50%可能性什么也得不到。在第二个实验中(C/D)，隐含的财富参考点是2023（即，假设你刚刚赢了2023元）。博彩C：肯定损失1000元;博彩D：50%可能性损失2023元，50%可能性什么也不损失。在不确定条件下，行为人的决策不仅与不同行动的期望效用有关，更与行为对基准点的偏离方向有关。三、分离效应

(isolationeffect)考虑一个两阶段的博彩：在博彩第一阶段，个人有75%的概率出局得不到任何回报，只有25%人进入下个阶段；第二阶段，在下面两个博彩间进行选择：博彩A：80%的机会得到4000元；博彩B：100%的机会得到3000元。现在，考虑下面只有一个阶段的两个博彩：博彩C：20%的机会得到4000元；博彩D：25%的机会得到3000元。三、分离效应

(isolationeffect)问卷的结果显示有78%的受访者选择博彩B，即：25%×80%×U(4000)<25%×100%×U(3000)→20%×U(4000)<25%×(3000)问卷显示大部分人选择了博彩C，即：20%×U(4000)>25%×(3000)由此可知道，在两阶段博弈当中个人有短视（myopia）现象，只考虑第二阶段而忽视了第一阶段。如果根据期望效用理论，这两个博彩的回报是相同的。但是由于问题的叙述方式不同，个人的选择是不同的，这就是框架效应的结果。四、框架效应

(Framingeffects)框架效应的例子：有个吝啬鬼不小心掉进河里，好心人趴在岸边喊到“快把手给我，我把你拉上来！”但这吝啬鬼就是不肯伸出自己的手。好心人开始很纳闷，后来突然醒悟，就冲着快要下沉的吝啬鬼大喊“我把手给你，你快抓住我！”，这吝啬鬼一下就抓住了这个好心人的手。心理学上把这种由于不一样表达导致不一样结果的现象称为“框架效应”。“框架效应”告诉我们：在人际沟通中，关键不在于说什么，而在于怎么说。四、框架效应

(Framingeffects)“亚洲疾病问题”实验：想象美国正准备对付一种罕见的亚洲疾病，预计该疾病的发作将导致600人死亡。现有两种与疾病作斗争的方案可供选择。假定对各方案所产生后果的精确科学估算如下所示。情景一：对第一组被试（N=152）叙述下面情景：如果采用A方案，200人将生还。（72%）如果采用B方案，有1/3的机会600人将生还，而有2/3的机会无人将生还。（28%）情景二：对第二组被试（N=155）叙述同样的情景，同时将解决方案改为C和D：如果采用C方案，400人将死去。（22%）如果采用D方案，有1/3的机会无人将死去，而有2/3的机会600人将死去。（78%）价值函数

(ValueFunction)Kahneman和Tversky(1979)给出的价值函数的指数形式如下：其中：α和β分别表示收益和损失区域价值幂函数的凹凸程度;系数λ>1表示损失区域比收益区域更陡的特征。效用理论的改进模型与

前景理论模型效用理论(Bernoulli)和期望效用理论(VonNeumannandMorgenstern)认为，人们对待风险的态度始终不变，其效用函数自始至终为凹形（图A）。弗里德曼和萨维奇提供了一个既有凹形部分又有凸形部分的效用函数来解决保险与彩票的困惑（图B)。马柯维茨通过将效用函数的一个拐点放在“通用财富”(customarywealth)的位置上修改了弗里德曼和萨维奇的函数（图C)。卡尼曼和特维斯基(KahnemanandTversky)在马柯维茨的通常财富理论和阿莱斯(Allais)工作的基础上构造了“前景理论”(prospecttheory)（图D）。ABCD决策权函数

(DecisionWeightFunction)1.2.Kahneman和Tversky(1979)给出的决策权函数的形式如下：决策权函数π(p)

具有“确定性效应(certaintyeffect)期望效用理论(EU)认为：某一事件的概率1个百分点的增量，应该对结果的权重具有同样的影响，无论最初的概率是0%，41%还是99%。p=0.0至p=0.1，p=0.4至p=0.5与p=0.9至p=1.0是相同的。

前景理论(PT)则认为：人们对概率的评价上存在“确定性效应”。由确定性到不确定性的变化给人感觉的效力很大：比如，由p=0.0至p=0.1这10%的变化给人感觉的效力很大。由不确定性到不确定性的变化带给人感觉的效力较小：比如，由p=0.4至p=0.5这10%的变化可能是微不足道的。由不确定到确定性的变化给人感觉的效力很大：比如，由p=0.9至p=1.0这10%的变化给人感觉的效力很大。决策权函数π(p)

是一个非线性函数“确定性效应”导致权重函数的非线性。因此，前景理论将决策权重看作概率P的一个非线性函数：π(p)。决策权重函数具有以下特点：（1）决策权重不是概率，它并不符合概率公理。（2）π(p)是p的增函数，且π(0)=0，π(1)=1，即不可能事件的偶发性是被忽略的，且度量是标准化的。（3）决策权重倾向于高估小概率事件（π(p)＞P）和低估高概率事件（π(p)＜P），即很不可能的事情却被赋予了很多的权重，很有可能的事情却被赋予低的权重；在中间阶段人们对概率的变化不敏感。期望效用理论vs.前景理论卡尼曼和特沃斯基(1986)认为，事实上两种方法都是必需的：期望效用理论描绘了理性行为的特征；而前景理论则描述了有限理性人的实际行为。期望效用理论为某些简单、透明的决策问题提供了标准；但大多数现实生活中的决策问题是复杂的，需要更加丰富的行为模型。

7.4行为决策的应用一、心里帐户(mentalaccounting)二、交易偏见(Exchangebiasorexchangeanisotropy)三、沉没成本误区(sunkcostfallacy)四、禀赋效应(EndowmentEffect)五、过度自信(Overconfidence)Decision-making,beliefandbehavioralbiases(1/8)Ambiguityeffect–thetendencytoavoidoptionsforwhichmissinginformationmakestheprobabilityseem"unknown."[8]Anchoringorfocalism–thetendencytorelytooheavily,or"anchor,"onapastreferenceorononetraitorpieceofinformationwhenmakingdecisions.Attentionalbias–thetendencytopayattentiontoemotionallydominantstimuliinone'senvironmentandtoneglectrelevantdata,whenmakingjudgmentsofacorrelationorassociation.Availabilityheuristic–thetendencytooverestimatethelikelihoodofeventswithgreater"availability"inmemory,whichcanbeinfluencedbyhowrecentthememoriesare,orhowunusualoremotionallychargedtheymaybe.Availabilitycascade–aself-reinforcingprocessinwhichacollectivebeliefgainsmoreandmoreplausibilitythroughitsincreasingrepetitioninpublicdiscourse(or"repeatsomethinglongenoughanditwillbecometrue").Backfireeffect–whenpeoplereacttodisconfirmingevidencebystrengtheningtheirbeliefs.[9]Bandwagoneffect–thetendencytodo(orbelieve)thingsbecausemanyotherpeopledo(orbelieve)thesame.Relatedtogroupthinkandherdbehavior.Baseratefallacyorbaserateneglect–thetendencytobasejudgmentsonspecifics,ignoringgeneralstatisticalinformation.[10]Beliefbias–aneffectwheresomeone'sevaluationofthelogicalstrengthofanargumentisbiasedbythebelievabilityoftheconclusion.[11]Biasblindspot–thetendencytoseeoneselfaslessbiasedthanotherpeople,ortobeabletoidentifymorecognitivebiasesinothersthaninoneself.[12]Decision-making,beliefandbehavioralbiases(2/8)Choice-supportivebias–thetendencytorememberone'schoicesasbetterthantheyactuallywere.[13]Clusteringillusion–thetendencytoover-expectsmallruns,streaksorclustersinlargesamplesofrandomdataConfirmationbias–thetendencytosearchfororinterpretinformationormemoriesinawaythatconfirmsone'spreconceptions.[14]Congruencebias–thetendencytotesthypothesesexclusivelythroughdirecttesting,insteadoftestingpossiblealternativehypotheses.Conjunctionfallacy–thetendencytoassumethatspecificconditionsaremoreprobablethangeneralones.[15]Conservatismorregressivebias–tendencytounderestimatehighvaluesandhighlikelihoods/probabilities/frequenciesandoverestimatelowones.Basedontheobservedevidence,estimatesarenotextremeenough[16][17][18]Conservatism(Bayesian)–thetendencytorevisebeliefinsufficientlywhenpresentedwithnewevidence(estimatesofconditionalprobabilitiesareconservative)[16][19][20]Contrasteffect–theenhancementordiminishingofaweightorothermeasurementwhencomparedwitharecentlyobservedcontrastingobject.[21]Curseofknowledge–whenknowledgeofatopicdiminishesone'sabilitytothinkaboutitfromaless-informedperspective.Decoyeffect–preferenceschangewhenthereisathirdoptionthatisasymmetricallydominatedDenominationeffect–thetendencytospendmoremoneywhenitisdenominatedinsmallamounts(e.g.coins)ratherthanlargeamounts(e.g.bills).[22]Distinctionbias–thetendencytoviewtwooptionsasmoredissimilarwhenevaluatingthemsimultaneouslythanwhenevaluatingthemseparately.[23]Durationneglect–theneglectofthedurationofanepisodeindeterminingitsvalueDecision-making,beliefandbehavioralbiases(3/8)Empathygap–thetendencytounderestimatetheinfluenceorstrengthoffeelings,ineitheroneselforothers.Endowmenteffect–thefactthatpeopleoftendemandmuchmoretogiveupanobjectthantheywouldbewillingtopaytoacquireit.[24]Essentialism–categorizingpeopleandthingsaccordingtotheiressentialnature,inspiteofvariations.[25]Exaggeratedexpectation–basedontheestimates,real-worldevidenceturnsouttobelessextremethanourexpectations(conditionallyinverseoftheconservatismbias).[16][26]Experimenter'sorexpectationbias–thetendencyforexperimenterstobelieve,certify,andpublishdatathatagreewiththeirexpectationsfortheoutcomeofanexperiment,andtodisbelieve,discard,ordowngradethecorrespondingweightingsfordatathatappeartoconflictwiththoseexpectations.[27]False-consensuseffect-thetendencyofapersontooverestimatehowmuchotherpeopleagreewithhimorher.Functionalfixedness-limitsapersontousinganobjectonlyinthewayitistraditionallyusedFocusingeffect–thetendencytoplacetoomuchimportanceononeaspectofanevent;causeserrorinaccuratelypredictingtheutilityofafutureoutcome.[28]ForereffectorBarnumeffect–theobservationthatindividualswillgivehighaccuracyratingstodescriptionsoftheirpersonalitythatsupposedlyaretailoredspecificallyforthem,butareinfactvagueandgeneralenoughtoapplytoawiderangeofpeople.Thiseffectcanprovideapartialexplanationforthewidespreadacceptanceofsomebeliefsandpractices,suchasastrology,fortunetelling,graphology,andsometypesofpersonalitytests.Framingeffect–drawingdifferentconclusionsfromthesameinformation,dependingonhoworbywhomthatinformationispresented.Frequencyillusion–theillusioninwhichaword,anameorotherthingthathasrecentlycometoone'sattentionsuddenlyseemstoappearwithimprobablefrequencyshortlyafterwards.(seealsorecencyillusion).[29]Decision-making,beliefandbehavioralbiases(4/8)Gambler'sfallacy–thetendencytothinkthatfutureprobabilitiesarealteredbypastevents,wheninrealitytheyareunchanged.Resultsfromanerroneousconceptualizationofthelawoflargenumbers.Forexample,"I'veflippedheadswiththiscoinfivetimesconsecutively,sothechanceoftailscomingoutonthesixthflipismuchgreaterthanheads."Hard-easyeffect–Basedonaspecificleveloftaskdifficulty,theconfidenceinjudgmentsistooconservativeandnotextremeenough[16][30][31][32]Hindsightbias–sometimescalledthe"I-knew-it-all-along"effect,thetendencytoseepasteventsasbeingpredictable[33]atthetimethoseeventshappened.Colloquiallyreferredtoas"Hindsightis20/20".Hostilemediaeffect–thetendencytoseeamediareportasbeingbiased,owingtoone'sownstrongpartisanviews.Hot-handfallacy-The"hot-handfallacy"(alsoknownasthe"hothandphenomenon"or"hothand")isthefallaciousbeliefthatapersonwhohasexperiencedsuccesshasagreaterchanceoffurthersuccessinadditionalattemptsHyperbolicdiscounting–thetendencyforpeopletohaveastrongerpreferenceformoreimmediatepayoffsrelativetolaterpayoffs,wherethetendencyincreasestheclosertothepresentbothpayoffsare.[34]Alsoknownascurrentmomentbias,present-bias,andrelatedtoDynamicinconsistency.Illusionofcontrol–thetendencytooverestimateone'sdegreeofinfluenceoverotherexternalevents.[35]Illusionofvalidity–whenconsistentbutpredictivelyweakdataleadstoconfidentpredictionsIllusorycorrelation–inaccuratelyperceivingarelationshipbetweentwounrelatedevents.[36][37]Impactbias–thetendencytooverestimatethelengthortheintensityoftheimpactoffuturefeelingstates.[38]Informationbias–thetendencytoseekinformationevenwhenitcannotaffectaction.[39]Insensitivitytosamplesize–thetendencytounder-expectvariationinsmallsamplesIrrationalescalation–thephenomenonwherepeoplejustifyincreasedinvestmentinadecision,basedonthecumulativepriorinvestment,despitenewevidencesuggestingthatthedecisionwasprobablywrong.Decision-making,beliefandbehavioralbiases(5/8)Just-worldhypothesis–thetendencyforpeopletowanttobelievethattheworldisfundamentallyjust,causingthemtorationalizeanotherwiseinexplicableinjusticeasdeservedbythevictim(s).Less-is-bettereffect–apreferencereversalwhereadominatedsmallersetispreferredtoalargersetLossaversion–"thedisutilityofgivingupanobjectisgreaterthantheutilityassociatedwithacquiringit".[40](seealsoSunkcosteffectsandendowmenteffect).Ludicfallacy-themisuseofgamestomodelreal-lifesituations.Mereexposureeffect–thetendencytoexpressunduelikingforthingsmerelybecauseoffamiliaritywiththem.[41]Moneyillusion–thetendencytoconcentrateonthenominal(facevalue)ofmoneyratherthanitsvalueintermsofpurchasingpower.[42]Moralcredentialeffect–thetendencyofatrackrecordofnon-prejudicetoincreasesubsequentprejudice.Negativitybias–thetendencytopaymoreattentionandgivemoreweighttonegativethanpositiveexperiencesorotherkindsofinformation.Neglectofprobability–thetendencytocompletelydisregardprobabilitywhenmakingadecisionunderuncertainty.[43]Nonsensematheffect-thetendencytojudgeinformationcontainingequationshigherregardlessthequalityofthem.[44]Normalcybias–therefusaltoplanfor,orreactto,adisasterwhichhasneverhappenedbefore.Decision-making,beliefandbehavioralbiases(6/8)Observationselectionbias–theeffectofsuddenlynoticingthingsthatwerenotnoticedpreviously—andasaresultwronglyassumingthatthefrequencyhasincreased.Observer-expectancyeffect–whenaresearcherexpectsagivenresultandthereforeunconsciouslymanipulatesanexperimentormisinterpretsdatainordertofindit(seealsosubject-expectancyeffect).Omissionbias–thetendencytojudgeharmfulactionsasworse,orlessmoral,thanequallyharmfulomissions(inactions).[45]Optimismbias–thetendencytobeover-optimistic,overestimatingfavorableandpleasingoutcomes(seealsowishfulthinking,valenceeffect,positiveoutcomebias).[46][47]Ostricheffect–ignoringanobvious(negative)situation.Outcomebias–thetendencytojudgeadecisionbyitseventualoutcomeinsteadofbasedonthequalityofthedecisionatthetimeitwasmade.Overconfidenceeffect–excessiveconfidenceinone'sownanswerstoquestions.Forexample,forcertaintypesofquestions,answersthatpeoplerateas"99%certain"turnouttobewrong40%ofthetime.[16][48][49][50]Pareidolia–avagueandrandomstimulus(oftenanimageorsound)isperceivedassignificant,e.g.,seeingimagesofanimalsorfacesinclouds,themaninthemoon,andhearingnon-existenthiddenmessagesonrecordsplayedinreverse.Pessimismbias–thetendencyforsomepeople,especiallythosesufferingfromdepression,tooverestimatethelikelihoodofnegativethingshappeningtothem.Planningfallacy–thetendencytounderestimatetask-completiontimes.[38]Post-purchaserationalization–thetendencytopersuadeoneselfthroughrationalargumentthatapurchasewasagoodvalue.Pro-innovationbias–thetendencytoreflectapersonalbiastowardsaninvention/innovation,whileoftenfailingtoidentifylimitationsandweaknessesoraddressthepossibilityoffailure.Pseuertaintyeffect–thetendencytomakerisk-aversechoicesiftheexpectedoutcomeispositive,butmakerisk-seekingchoicestoavoidnegativeoutcomes.[51]Decision-making,beliefandbehavioralbiases(7/8)Reactance–theurgetodotheoppositeofwhatsomeonewantsyoutodooutofaneedtoresistaperceivedattempttoconstrainyourfreedomofchoice(seealsoReversepsychology).Reactivedevaluation–devaluingproposalsthatarenolongerhypotheticalorpurportedlyoriginatedwithanadversary.Recencybias–acognitivebiasthatresultsfromdisproportionatesalienceattributedtorecentstimuliorobservations–thetendencytoweighrecenteventsmorethanearlierevents(seealsopeak-endrule,recencyeffect).Recencyillusion–theillusionthataphenomenon,typicallyawordorlanguageusage,thatonehasjustbeguntonoticeisarecentinnovation(seealsofrequencyillusion).Restraintbias–thetendencytooverestimateone'sabilitytoshowrestraintinthefaceoftemptation.Rhymeasreasoneffect–rhymingstatementsareperceivedasmoretruthful.AfamousexamplebeingusedintheO.JSimpsontrialwiththedefensesuseofthephrase"Iftheglovesdon'tfitthenyoumustacquit."Riskcompensation/Peltzmaneffect–thetendencytotakegreaterriskswhenperceivedsafetyincreases.Selectiveperception–thetendencyforexpectationstoaffectperception.Semmelweisreflex–thetendencytorejectnewevidencethatcontradictsaparadigm.[52]Selectionbias-thedistortionofastatisticalanalysis,resultingfromthemethodofcollectingsamples.Iftheselectionbiasisnottakenintoaccountthencertainconclusionsdrawnmaybewrong.Socialcomparisonbias–thetendency,whenmakinghiringdecisions,tofavourpotentialcandidateswhodon'tcompetewithone'sownparticularstrengths.[53]Socialdesirabilitybias-thetendencytoover-reportsociallydesirablecharacteristicsorbehavioursandunder-reportsociallyundesirablecharacteristicsorbehaviours.[54]Decision-making,beliefandbehavioralbiases(8/8)Statusquobias–thetendencytolikethingstostayrelativelythesame(seealsolossaversion,endowmenteffect,andsystemjustification).[55][56]Stereotyping–expectingamemberofagrouptohavecertaincharacteristicswithouthavingactualinformationaboutthatindividual.Subadditivityeffect–thetendencytoestimatethatthelikelihoodofaneventislessthanthesumofits(morethantwo)mutuallyexclusivecomponents.[57]Subjectivevalidation–perceptionthatsomethingistrueifasubject'sbeliefdemandsittobetrue.Alsoassignsperceivedconnectionsbetweencoincidences.Survivorshipbias-concentratingonthepeopleorthingsthat"survived"someprocessandinadvertentlyoverlookingthosethatdidn'tbecauseoftheirlackofvisibility.Texassharpshooterfallacy-piecesofinformationthathavenorelationshiptooneanotherarecalledoutfortheirsimilarities,andthatsimilarityisusedforclaimingtheexistenceofapattern.Time-savingbias–underestimationsofthetimethatcouldbesaved(orlost)whenincreasing(ordecreasing)fromarelativelylowspeedandoverestimationsofthetimethatcouldbesaved(orlost)whenincreasing(ordecreasing)fromarelativelyhighspeed.Unitbias–thetendencytowanttofinishagivenunitofataskoranitem.Strongeffectsontheconsumptionoffoodinparticular.[58]Welltravelledroadeffect–underestimationofthedurationtakentotraverseoft-traveledroutesandoverestimationofthedurationtakentotraverselessfamiliarroutes.Zero-riskbias–preferenceforreducingasmallrisktozerooveragreaterreductioninalargerrisk.Zero-sumheuristic–Intuitivelyjudgingasituationtobezero-sum(i.e.,thatgainsandlossesarecorrelated).Derivesfromthezero-sumgameingametheory,wherewinsandlossessumtozero.[59][60]Thefrequencywithwhichthisbiasoccursmayberelatedtothesocialdominanceorientationpersonalityfactor.Socialbiases(1/3)Actor-observerbias–thetendencyforexplanationsofotherindividuals'behaviorstooveremphasizetheinfluenceoftheirpersonalityandunderemphasizetheinfluenceoftheirsituation(seealsoFundamentalattributionerror),andforexplanationsofone'sownbehaviorstodotheopposite(thatis,tooveremphasizetheinfluenceofoursituationandunderemphasizetheinfluenceofourownpersonality).Defensiveattributionhypothesis–defensiveattributionsaremadewhenindividualswitnessorlearnofamishaphappeningtoanotherperson.Inthesesituations,attributionsofresponsibilitytothevictimorharm-doerforthemishapwilldependupontheseverityoftheoutcomesofthemishapandthelevelofpersonalandsituationalsimilaritybetweentheindividualandvictim.Moreresponsibilitywillbeattributedtotheharm-doerastheoutcomebecomesmoresevere,andaspersonalorsituationalsimilaritydecreases.Dunning–Krugereffectaneffectinwhichincompetentpeoplefailtorealisetheyareincompetentbecausetheylacktheskilltodistinguishbetweencompetenceandincompetence[61]Egocentricbias–occurswhenpeopleclaimmoreresponsibilityforthemselvesfortheresultsofajointactionthananoutsideobserverwouldcreditthem.Extrinsicincentivesbias–anexceptiontothefundamentalattributionerror,whenpeopleviewothersashaving(situational)extrinsicmotivationsand(dispositional)intrinsicmotivationsforoneselfFalseconsensuseffect–thetendencyforpeopletooverestimatethedegreetowhichothersagreewiththem.[62]Forereffect(akaBarnumeffect)–thetendencytogivehighaccuracyratingstodescriptionsoftheirpersonalitythatsupposedlyaretailoredspecificallyforthem,butareinfactvagueandgeneralenoughtoapplytoawiderangeofpeople.Forexample,horoscopes.Socialbiases(2/3)Fundamentalattributionerror–thetendencyforpeopletoover-emphasizepersonality-basedexplanationsforbehaviorsobservedinotherswhileunder-emphasizingtheroleandpowerofsituationalinfluencesonthesamebehavior(seealsoactor-observerbias,groupattributionerror,positivityeffect,andnegativityeffect).[63]Groupattributionerror–thetendencytoassumethatgroupdecisionoutcomesreflectthepreferencesofgroupmembers,evenwheninformationisavailablethatclearlysuggestsotherwise.Haloeffect–thetendencyforaperson'spositiveornegativetraitsto"spillover"fromoneareaoftheirpersonalitytoanotherinothers'perceptionsofthem(seealsophysicalattractivenessstereotype).[64]Illusionofasymmetricinsight–peopleperceivetheirknowledgeoftheirpeerstosurpasstheirpeers'knowledgeofthem.[65]Illusionofexternalagency–whenpeopleviewself-generatedpreferencesasinsteadbeingcausedbyinsightful,effectiveandbenevolentagentsIllusionoftransparency–peopleoverestimateothers'abilitytoknowthem,andtheyalsooverestimatetheirabilitytoknowothers.Illusorysuperiority–overestimatingone'sdesirablequalities,andunderestimatingundesirablequalities,relativetootherpeople.(Alsoknownas"LakeWobegoneffect,""better-than-averageeffect,"or"superioritybias").[66]Ingroupbias–thetendencyforpeopletogivepreferentialtreatmenttootherstheyperceivetobemembersoftheirowngroups.Socialbiases(3/3)Just-worldphenomenon–thetendencyforpeopletobelievethattheworldisjustandthereforepeople"getwhattheydeserve."Moralluck–thetendencyforpeopletoascribegreaterorlessermoralstandingbasedontheoutcomeofaneventratherthantheintentionNaivecynicism–expectingmore