IntroductiontoBehavioralEconomics复旦行为经济学课件

IntroductiontoBehavioralEconomics

行为经济学

方向博士OklahomaStateUniversityIntroductiontoBehavioralEco参考书作者:孙惟微：独立经济学者，策略顾问、熙代（北京）文化传媒有限公司执行董事。参考书作者:孙惟微：独立经济学者，策略顾问、熙代（北京）文董志勇

(作者)

董志勇(作者)

丹·艾瑞里

丹·艾瑞里

AShortSurveyFocusingfornowonindividualdecisions,whatdoesmainstream(standardneoclassical)economicsnormallyassume?AShortSurveyFocusingfornowAssumptionsRationality无限理性:Isperfectlyrational,makingchoicesthatconsistentlymaximizesomeexogenous,stablesetofpreferencesthatdependonabsolutelevelsofoutcomes(ratherthanchanges).经济学假设个人具有稳定和连续的偏好，并用无限理性使这些偏好最大化Self-Interest无限自私自利:Isalmostalwaysalsoassumedtobeperfectlyself-interested,caringexclusivelyabouther/hisownconsumption,thoughthisassumptionisnotessentialtomainstreamtheory.

Self-Control无限意志力:Hasperfectwill-powerandtheabilitytomakeandfollowintertemporalplans(evencontingentones),withnoconflictbetweenthepreferencesofcurrentandfutureselves.AssumptionsRationality无限理性:I而行为经济学正是基于对以上三个“无限性”的反对提出了自己关于非理性人的新观点1。正常生活中的经济个体应该是非理性的，这样一个非理性的人，并不具备稳定和连续的偏好以及使这些偏好最大化的无限理性；2。即使知道效用最大化的最优解也有可能因为自我控制意志力方面的原因而无法做出相应的最优决策；3。其经济决策的过程中包含了相当的非物质动机和非经济动机权重，人们会愿意牺牲自己的利益去帮助他人。而行为经济学正是基于对以上三个“无限性”的反对提出了自己关于行为经济学的兴起主要有三方面的原因第一是基于对精神心理因素的研究。现代经济学向心理学靠拢,同现代经济中的精神心理因素有关，与现代经济的日益“非物质化”、“商品的个性化”有关。行为经济学的兴起主要有三方面的原因第一是基于对精神心理因素第二，行为经济学拓宽了正统经济学的领域。经济学家一向认为人是理性的动物，即人总是倾向于追求最大收益或承担最小成本。但人类行为固然有其理性一面，也有其非理性的一面。所以，非理性行为可用科学的方法加以研究。(“不买最好的，只买最贵的。”)第二，行为经济学拓宽了正统经济学的领域。经济学家一向认为人是第三，传统经济学认为，经济学是一门研究财富的学问；而现代经济学提出，经济学也是一门研究人的学问。人类社会化的行为受复杂的社会关系制约，从而导致人的行为选择并非都是建立在理性思考的基础上。因此从纯理性研究人的行为行不通。从经济主体讲，经济过程最终体现为人的经济行为过程，因而对人的分析离不开用人的心理对其行为的解释。第三，传统经济学认为，经济学是一门研究财富的学问；而现代经济亚当斯密AdamSmith每个人都力求运用自己的资本，生产出最大的价值。一般而来，他不会为了促进公共利益，也不知道促进多少。他只考虑自己的安全，自己的所得。正是这样，他由一只看不见的手引导着，实现着他自己并不打算实现的目标。与有意地促进相比，在追求他自己得利益的过程中，往往能够更加有效地促进社会得公益。亚当斯密AdamSmith每个人都力求运用自己的资本，生直到最近，经济学尚被普遍看作一种必须依赖于对现实世界的观察、而不能依靠在实验室里做受控制的实验来进行研究的非实验性科学。许多评论者发现受利己主义和理性决策所支配的“经济人”(homooeconomicus)这一普遍假设存在局限性。然而，经济学研究已经开始朝着新的方向起飞。大量和日益增多的科学工作致力于对经济学传统的基本假设的经验检验和修改，特别是有关无限理性、纯粹利己主义和完全自治的假设。直到最近，经济学尚被普遍看作一种必须依赖于对现实世界的观察、而且，目前的研究越来越依赖于来自实验室的新的实验数据，而不是从对实际经济的观察中所得到的传统的现场数据。最近的这些研究源于两个区别显著、但正趋于一致的传统：一是认知心理学中有关个人决策的理论和经验研究；二是以实验的方法对经济理论预言的检验。行为经济学和实验经济学已经跻身于经济学最活跃的领域之列。2002的诺贝尔经济学奖得主就是在这两个领域从事研究的前辈。而且，目前的研究越来越依赖于来自实验室的新的实验数据，而不是2002:VernonSmithandDanielKahnemanreceivedtheNobelPrizeVernonSmith:“fortheuseoflaboratoryexperimentsasatoolinempiricaleconomicanalysis,inparticular,forthestudyofdifferentmarketmechanisms.”Founderofexperimentaleconomics.DanielKahneman:“fortheintroductionofinsightsfrompsychologicalresearchintoeconomics,inparticularwithregardtojudgmentsanddecisionsunderuncertainty.”Kahneman’sresearchisbasedonpsychologicalexperimentsandquestionnaires.Founderofbehavioraleconomics.2002:VernonSmithandDaniel实验经济学传统上，经济学被看作一种完全依赖现场数据的非实验性科学。许多人认为，这一点是经济学作为一门科学继续发展的障碍。除非我们可以进行受控制的实验，否则对经济理论的检验将永远是有限的。仅仅根据现场数据，人们很难判断一个理论是否失败或何时失败，并正确地指出失败的原因。在理论与受控制的实验观察两者之间的反馈渠道在经济学中基本不存在。一种新兴的、被称作“实验经济学”的研究领域的建立从根本上对这一观点提出了挑战。在受控制的实验室里，实验者以简单、抽象的形式模仿在市场和其他经济交往形式中出现的场景，以研究这些场景中的人类行为。实验经济学传统上，经济学被看作一种完全依赖现场数据的非实验性实验经济学的历史早年已有前辈学者从事经济学的实验研究。50多年前，张伯伦(Chamberlin，1948)试图通过实验来检验新古典的完全竞争理论。约翰·纳什(JohnNash)——1994年诺贝尔经济学奖得主——与他的同事通过设置一个实验对博弈论的预测能力进行了早期研究。实验经济学的历史早年已有前辈学者从事经济学的实验研究。50多弗农·史密斯在亚利桑那大学十一个班级进行了长达六年的实验，验证了竞争均衡理论。据此实验所撰写的论文《竞争市场行为的实验研究》在1962年的《政治经济学杂志》发表，标志着实验经济学的诞生。弗农·史密斯在亚利桑那大学十一个班级进行了长达六年的实验，验弗农·史密斯的意义最重大的工作涉及市场机制。他对竞争性市场所做的创新性实验(1962)、对不同拍卖形式的检验(1965，1976，1980)，以及对“诱导价值法”(induced-value，1976)的设计，都为这一领域的研究奠定了基础。弗农·史密斯的意义最重大的工作涉及市场机制。他对竞争性市场所查尔斯·普洛特认为：“实验室建立的经济与现实经济相比可能特别简单，但是却一样地真实。真实的人被真实的金钱所驱动，因为真实的天赋和真实的局限，作出真实的决策和真实的错误，并为其行为后果而真实地悲喜”。查尔斯·普洛特认为：“实验室建立的经济与现实经济相比可能特别HistoryofBehavioralEconomics

行为经济学历史AdamSmith,whoisbestknownfortheconceptofthe"invisiblehand"andTheWealthofNations,wrotealesswell-knownbookTheTheoryofMoralSentiments(《道德情操论》),whichlaidoutpsychologicalprinciplesofindividualbehaviorthatarearguablyasprofoundashiseconomicobservations.Forexample,AdamSmithcommented(1759/1892,311)that"wesuffermore...whenwefallfromabettertoaworsesituation,thanweeverenjoywhenwerisefromaworsetoabetter.”Lossaversion!损失厌恶HistoryofBehavioralEconomic认知心理学的发展Beginningaround1960,cognitivepsychologybecamedominatedbythemetaphorofthebrainasaninformation-processingdevicereplacingthebehavioristconceptionofthebrainasastimulus-responsemachine.Theinformation-processingmetaphorpermittedafreshstudyofneglectedtopicslikememory,problemsolvinganddecisionmaking.Thesenewtopicsweremoreobviouslyrelevanttotheneoclassicalconceptionofutilitymaximizationthanbehaviorismhadappearedtobe.认知心理学的发展Beginningaround1960,HerbertSimon西蒙现代决策理论的奠基人–卡内基大学教授西蒙，心理学家和人工智能的创立者批判理性经济人的假设，提出“有限理性”(boundedrationality)概念,获得1978年诺贝尔奖。西蒙指出了新古典经济学理论的不现实之处，分析了它的两个致命弱点：(1)假定目前状况与未来变化具有必然的一致性；(2)假定全部可供选择的“备选方案”和“策略”的可能结果都是已知的。HerbertSimon西蒙现代决策理论的奠基人–卡有限理性人的有限性包括两个方面的含义，一是环境是复杂的，在非个人交换形式中，人们面临的是一个复杂的、不确定的世界，而且交易越多，不确定性就越大，信息也就越不完全；二是人对环境的计算能力和认识能力是有限的，人不可能无所不知。西蒙认为,人们在决定过程中寻找的并非是“最优”的标准，而只是“满意”的标准。有限理性人的有限性包括两个方面的含义，一是环境是复杂的，在非TverskyandKahnemanPerhapsthetwomostinfluentialcontributionswerepublishedbyTverskyandKahneman.Their1974Sciencearticlearguedthatheuristicshort-cutscreatedprobabilityjudgmentswhichdeviatedfromstatisticalprinciples.(AmosTverskyandDanielKahneman,“JudgmentunderUncertainty:HeuristicsandBiases,”Science185(1974),pp.1124–1131)Their1979paper"Prospecttheory:decisionmakingunderrisk"documentedviolationsofexpectedutilityandproposedanaxiomatictheory,groundedinpsychophysicalprinciples,toexplaintheviolations.ItwaspublishedinthetechnicaljournalEconometricaandisoneofthemostwidelycitedpaperseverpublishedinthatjournal.TverskyandKahnemanPerhapsthStepsthatearlyBEresearchtookFirst,identifynormativeassumptionsormodelsthatareubiquitouslyusedbyeconomists,suchasBayesianupdating,expectedutilityanddiscountedutility.Second,identifyanomalies—i.e.,demonstrateclearviolationsoftheassumptionormodel,andpainstakinglyruleoutalternativeexplanations(suchassubjects’confusionortransactionscosts).Third,usetheanomaliesasinspirationtocreatealternativetheoriesthatgeneralizeexistingmodels.Afourthstepistoconstructeconomicmodelsofbehaviorusingthebehavioralassumptionsfromthethirdstep,derivefreshimplications,andtestthem.StepsthatearlyBEresearcht例子1A.你一定能赚30000元。

B.你有80%可能赚40000元，20%可能性什么也得不到。例子1A.你一定能赚30000元。例子2A.你一定会赔30000元。B.你有80%可能赔40000元，20%可能不赔钱。例子2A.你一定会赔30000元。例子3假设你面对这样一个选择：在商品和服务价格相同的情况下，你有两种选择：A.其他同事一年挣6万元的情况下，你的年收入7万元。B.其他同事年收入为9万元的情况下，你一年有8万元进账。例子3假设你面对这样一个选择：在商品和服务价格相同的情况下，认知心理学家考虑的是一个交互作用的过程，几个因素都会对决策产生重要影响，比如知觉、信仰或心智模式。诸如感情、态度等内在动机也会影响一项决策。此外，对以前决策及其后果的记忆是一个至关重要的认知函数。在这种复杂观点下，人类行为被认为是局部地适应于一个既定的环境。行为具有适应性，取决于环境和瞬间的感知状态。

卡尼曼等人通过调查和实验收集到的事实，对经济学的理性假设，至少是对复杂决策情景下的理性假设提出了质疑。例如，现实世界中的决策者不总是依据概率法则评价不确定前景，有时，制定决策会违背预期效用最大化原则。卡尼曼的贡献主要是关于不确定条件下的判断和决策。认知心理学家考虑的是一个交互作用的过程，几个因素都会对决策产阿莫斯·特维尔斯基(AmosTversky)，丹尼尔·卡尼曼(DanielKahneman)，里查德·萨勒(RichardH.Thaler)，马修·拉宾(MatthewRabin)，美籍华人奚恺元教授等是这一学科的开创性代表。阿莫斯·特维尔斯基(AmosTversky)，丹尼尔·卡总结丹尼尔·卡尼曼运用认知心理学中关于心理过程的深刻见解，帮助我们更好地理解了人们制定经济决策的行为。卡尼曼和特维尔斯基对不确定条件下决策行为的研究最有影响力。卡尼曼还对行为经济学等其他领域作出了开创性的贡献。卡尼曼已经成为近期在行为经济学和金融学研究领域中所出现的繁荣景象背后的一个主要灵感来源。他的研究对其他领域也产生了重大影响。

弗农·史密斯是开创以实验作为经济学经验方法论的一个最有影响的人物。与卡尼曼不同，他没有以挑战传统经济学理性决策理论而开始，而是检验了关于市场表现的假说。卡尼曼的调查和实验主要关注个人的决策，而史密斯则将实验的重点放在特定市场环境下人与人之间的相互作用上。他还强调了方法论问题，发展了具有实践性的实验方法，建立了构筑一个良好实验的标准。基于史密斯的成就，许多经济学家开始把实验室实验作为一个基本工具。

总结丹尼尔·卡尼曼运用认知心理学中关于心理过程的深刻见解，帮MainTopics前景理论(ProspectTheory)启发式与偏差(HeuristicsandBiases)锚定理论和现状偏见(AnchoringandAdjustment,StatusQuoBias)禀赋效应(EndowmentEffect)偏好理论(PreferenceReversal)时间贴现和跨期选择(TimeDiscountingandTimePreference)心理帐户(MentalAccounting)其他应用MainTopics前景理论(ProspectTheoExample:StatusQuoBias

现状偏见Decision-makershaveanoverwhelmingtendencytoadoptdefaults,tostickwiththestatusquoEvenwhenthedecisionisimportantandthestakesarelargeEvenwhenthedecision-makeristoldthatthedefaultissuboptimalExamplesfrom401(k)plans:participation,savingsrate,assetallocation(companystock).Otherexamples:insurancedeductibles,organdonationExample:StatusQuoBias

现状偏见BrigitteMadrianandDennisShea(2001)

Design:AFortune500CompanySwitched401(k)defaultonApril1,1998.MadrianandSheaexaminebehaviorofnewhires.

OLDDefaultContribution:MustactivelysignupDefaultAllocation:None

NEWDefaultContribution:3percentofcompensationdeductedforplanDefaultAllocation:MoneyMarketFundBrigitteMadrianandDennisSh401(k)ParticipationIncreases

PercentatSpecifiedContributionRateSource:MadrianandShea(2001).ContributionRate401(k)ParticipationIncreases401(k)AssetAllocationAlsoChangedSource:MadrianandShea(2001).PercentofAssets401(k)AssetAllocationAlsoCImpactofAutomaticEnrollmentin401(k)Before,DuringandAfterSource:Choi,Laibson,Madrian,Metrick(2004)ImpactofAutomaticEnrollmentPolicyApplication:PensionReformBillof2006

The900PensionProtectionActof2006comesasthenumberofpeoplecoveredbyadefined-benefitpensionhassteadilydeclinedandawarenesshasgrownaboutthelackofadequatesavingsamongAmericans. Amajorityofworkers45andolderhavelessthan$50,000insavings,accordingtoasurveybytheEmployeeBenefitResearchInstitute(EBRI).What'smore,almost40percentofworkersover40don'tparticipateina401(k)whentheyareeligible. Thenewlegislationencouragescompaniestoautomaticallyenroll401(k)-eligibleemployeesandtoautomaticallyincreaseworkercontributionseveryyear.Italsoallowstheplanproviderchosenbytheemployertoofferinvestmentadvicetoworkers. Automaticenrollmentisexpectedtoboosttheparticipationratein401(k)plansbeyond90percent. ByJeanneSahadi,CNNMLibertarian-Paternalism:Setthedefaulttohelppeople,buttheycanoptout.PolicyApplication:PensionRe“不满意七天可以退货”的商品;汽车行也会借车给人试驾。为救美国经济于水深火热，美联储主席伯南克有句名言：“如有必要，可用直升机撒钱。”意外之财地王

“不满意七天可以退货”的商品;汽车行也会借车给人试驾。IntroductiontoLabExperimentsIntroductiontoLabExperimentLabExperiments“Onepossiblewayoffiguringouteconomiclaws...isbycontrolledexperiments....Economists(unfortunately)...cannotperformthecontrolledexperimentsofchemistsorbiologistsbecausetheycannoteasilycontrolotherimportantfactors.Likeastronomersormeteorologists,theygenerallymustbecontentlargelytoobserve.”(SamuelsonandNordhaus,1985,p.8)“EconomicTheory,throughaformaldeductivesystem,providesthebasisforexperimentalabstractionandtheexperimentaldesign,butsocietyinmostcasescarriesouttheexperiment,Therefore,theeconomicresearcherobservestheoutcomeofsociety’sexperimentorperformancebuthaslittleornoimpactontheexperimentaldesignandtheobservationsgenerated.Thus,bythepassivenatureofthedata,economicresearchersare,toalargeextent,restrictedintheirknowledgesearchtotheprocessofnonexperimentalmodelbuilding....theexperimentisoutsidetheresearcher’scontrol.”(“TheNonexperimentalModel-BuildingRestriction”inJudgeetal.(1988))LabExperiments“OnepossiblewPhilosophyofscience:thescientificmethodPhilosophyHowweunderstandtheworldScienceA“method”forachievingthisgoalDevelopmentoftheoryFormulationofhypotheses-predictionsTestsofpredictionsDesign&AnalysisHowwetestpredictions ofhypothesesStatisticsToolforquantitativetestsPhilosophyofscience:thesciScience—AssumptionsRealismWorldissubjecttoinvestigationRationality—logicRegularityResultscanbegeneralizedCausality—worldisordered—determinismDiscoverabilityorknowabilityofcausesScience—AssumptionsRealismDefinitionsInduction(orinductivereasoning):reasoningthatgenerallawsexistbecauseparticularcasesthatseemtobeexamplesofitexistDeduction(ordeductivereasoning):reasoningthatsomethingmustbetruebecauseitisaparticularcaseofageneral(universal)lawknowntobetrue Inductionspecificgeneral deduction5swansseen,allarewhiteallswansarewhiteDefinitionsInduction(orinducTypesofResearchDesignThreetraditionalcategories:ExploratoryDescriptiveCausalThechoiceofthemostappropriatedesigndependslargelyontheobjectivesoftheresearchandhowmuchisknownabouttheproblemandresearchobjectives.TypesofResearchDesignThreeBasicResearchObjectivesandResearchDesignResearchObjective AppropriateDesignTogainbackgroundinformation, Exploratorytodefineterms,toclarify problemsandhypotheses,toestablishresearchprioritiesTodescribeandmeasuremarketing DescriptivephenomenaatapointintimeTodeterminecausality, Causaltomake“if-then”statements BasicResearchObjectivesandExploratoryResearchExploratoryresearchismostcommonlyunstructured,informalresearchthatisundertakentogainbackgroundinformationaboutthegeneralnatureoftheresearchproblem.Byunstructured,wemeanthereisnoformalsetofobjectives,sampleplan,orquestionnaire.ExploratoryResearchExploratorExploratoryResearchItisusuallyconductedwhentheresearcherdoesnotknowmuchabouttheproblems.Exploratoryresearchisusuallyconductedattheoutsetofresearchprojects.ExploratoryResearchItisusuaExploratoryResearchUsesGainBackgroundInformationDefineTermsClarifyProblemsandHypothesis(refineresearchobjectives)EstablishResearchPrioritiesManyquestions;manysourcesDefiningtheproblem;gettinga“feel”ExploratoryResearchManyquesExploratoryResearchAvarietyofmethodsareavailabletoconductexploratoryresearch.SecondaryDataAnalysisExperienceSurveysCaseAnalysisExploratoryResearchAvarietyDescriptiveResearchDescriptiveresearchisundertakentodescribeanswerstoquestionsofwho,what,where,when,andhow.Descriptiveresearchisdesirablewhenwewishtoprojectastudy’sfindingstoalargerpopulation,ifthestudy’ssampleisrepresentative.DescriptiveResearchDescriptivCausalResearchCausalitymaybethoughtofasunderstandingaphenomenonintermsofconditionalstatementsoftheform“Ifx,theny.”Causalstudiesareconductedthroughtheuseofexperiments.CausalResearchCausalitymaybExperimentsAnexperiment

isdefinedasmanipulatinganindependentvariabletoseehowitaffectsadependentvariable,whilealsocontrollingtheeffectsofadditionalextraneousvariables.ExperimentsAnexperimentisdeExample:OurPropositionHypothesis:SouthernwhitemalesaremorepronetoaggressionthanareNorthernwhitemales.(conjecture)We’lllookatdifferentstrategiestoexaminehypotheses.(refutation)Example:OurPropositionHypothRefutationputtingtheoriestothetestWhatevidencesupports(and,moreimportantly,disconfirms)ourtheories?RefutationputtingtheoriestoDescriptiveResearchassessestheamountoraveragelevelofagivenvariableinapopulatione.g.,publicopinionsurveysnotatruetestofanhypothesisWhatisthewhitemalehomiciderateintheSouth?DescriptiveResearchassessestDescriptiveResearchWhatisthewhitemalehomiciderateintheSouth?adaptedfromNisbett(1993)DescriptiveResearchWhatisthDescriptiveResearchcriticalissuesrandomsamplingbasisofcomparisoninformative,butnotahypothesistestWhatelsecouldaccountforthefindings?DescriptiveResearchcriticaliCorrelationalResearchinvestigateswhetherchangesinonevariablearerelatedtochangesinanothervariableWhatistherelationshipbetweenbeingfromtheSouthandaggressivebehavior?CorrelationalResearchinvestigCorrelationalResearchcorrelationcoefficientsrangefrom+1.00to-1.00positive

correlation:increase/decreaseinthesamedirectionCorrelationalResearchcorrelatCorrelationalResearchCorrelationalResearchCorrelationalResearchcorrelationcoefficientsrangefrom+1.00to-1.00negativecorrelation:increase/decreaseinoppositedirectionsCorrelationalResearchcorrelatCorrelationalResearchCorrelationalResearchCorrelationalResearchcorrelationcoefficientsrangefrom+1.00to-1.00strengthoftherelationship:closenessto+1.00/-1.00,notbythevalence(+/-)Whichindicatesastrongercorrelation:-.74or+.21?CorrelationalResearchcorrelatCorrelationalResearchCorrelationalResearchCorrelationalResearchWhatistherelationshipbetweenbeingfromtheSouthandaggressivebehavior?Nisbett(1993)homiciderateand“southernness”: rs=.37inthesocialsciences(Cohen,1992)

r=.50(strong)r=.30(moderate)r=.10(small)CorrelationalResearchWhatisCorrelationalResearchstrengthsofthisapproachcanbearandomsampleactualbehaviorhasgoodgeneralizability(i.e.,externalvalidity)potentialfornumerousvariablesCorrelationalResearchstrengthCorrelationalResearchweaknessofthisapproachcannotinferacause-effectrelationshipfactorsforinferringcausalityassociation--yestemporalpriority--noruleoutaspuriousrelationship--noCorrelationalResearchweaknessCorrelationalResearchtemporalprioritysouthernnesshomicideratestimeCorrelationalResearchtemporalCorrelationalResearchtemporalprioritysouthernnesshomiciderateshomicideratessouthernnessortimetimeCorrelationalResearchtemporalCorrelationalResearchtemporalprioritydirectionofcausalityproblemsouthernnesshomiciderateshomicideratessouthernnessortimetimeCorrelationalResearchtemporalCorrelationalResearchruleoutaspuriousrelationshipsouthernnesshomicideratesanothervariablespuriousCorrelationalResearchruleoutCorrelationalResearchruleoutaspuriousrelationshipsouthernnesshomicideratespovertyrs=.38&.42(Nisbett,1993)CorrelationalResearchruleoutCorrelationalResearchruleoutaspuriousrelationship3rdvariableproblemsouthernnesshomicideratesanothervariablespuriousCorrelationalResearchruleoutCorrelationalResearchstrengthspotentialfornumerousvariablesgoodgeneralizabilityweaknessescannotmakecausalconclusionsdirectionofcausality3rdvariableproblemCorrelationalResearchstrengthAddressingProblemswithCorrelationalResearchdirectionofcausalityproblemDoes“southernness”leadtomoreaggressionordoesapropensityforaggressionleadtomore“southernness”?solution:wecause(i.e.,manipulate)oneofthevariablesinsultonegrouponSoutherners,butnotanotherAddressingProblemswithCorreAddressingProblemswithCorrelationalResearchdirectionofcausalityproblemifwecontrolwhoisinsulted,thenmeasureaggressiveness,weknowthedirectionofcausalitybut,westillhavethe3rdvariableproblempoorsocialskillsAddressingProblemswithCorreAddressingProblemswithCorrelationalResearchrandomassignmenttoconditionifsocialskillshaveaneffectonaggression,itshouldbeequalforbothgroupsWecanaddresstheproblemsofcorrelationalresearchbydoingexperiments.AddressingProblemswithCorreExperimentalDesigncharacteristicsmanipulationofavariablesolvesthedirectionofcausalityproblemrandomlyassigntoconditionssolvesthe3rdvariableproblemExperimentalDesigncharacterisExperimentalDesigntestingtheoryDoestheindependentvariablecausechangesinthedependentvariable?southernnessaggressioncauseExperimentalDesigntestingtheExperimentalDesigntheSoutherncultureofhonorhypothesisCohenetal.(1996)2(Southern/Northern)X2(insult/noinsult)ExperimentalDesigntheSoutherExperimentalDesignInsultNoInsultDistanceatwhichparticipantsgavewaytoconfederate(inches)ExperimentalDesignInsultNoInExperimentalDesignInsultNoInsultDistanceatwhichparticipantsgavewaytoconfederate(inches)ExperimentalDesignInsultNoInExperimentalDesignstrengthsallowsforcausalconclusionstobemade--besttestoftheoryweaknessesnotallquestionsareamenabletoexperimentsconcernsaboutgeneralizabilityExperimentalDesignstrengthsSummaryrefutation:processoftestingtheoriesdescriptiveresearchisinformative,butlimitedintheorytestingcorrelationalresearchismoreinformative,butdoesnotallowforcausalexplanationsexperimentsarethebesttestoftheoriesSummaryrefutation:processofIndependentVariableIndependentvariables

are

thosevariableswhichtheresearcherhascontroloverandwishestomanipulate.Forexample:price,framing,incentive,etc.IndependentVariableIndependenDependentVariablesDependentvariables

are

thosevariablesthatwehavelittleornodirectcontrolover,yetwehaveastronginterestin.Exampleswouldbeoutput,choice,etc.DependentVariablesDependentvCausalRelationshipIndependentvariableDependentvariable(e.g.,TobaccoTax)(Consumption)CausalRelationshipExtraneousVariablesExtraneousvariablesarethosevariablesthatmayhavesomeeffectonadependentvariableyetarenotindependentvariables.Extraneousvariablesmustbecontrolledthroughproperexperimentaldesign.ExtraneousVariablesExtraneousExperimentalDesignExperimentaldesign

isaprocedurefordevisinganexperimentalsettingsuchthatachangeinadependentvariablemaybeattributedsolelytothechangeinanindependentvariable.ExperimentalDesignExperimentaValidityInternalValidityExternalValidityValidityInternalValidityInternalValidityAretheobservedeffectsontheD.V.acauseofthetreatment?Orcouldtheyhavebeencausedbysomethingelse?InternalValidityAretheobserExternalValiditywhethertheresultfromaparticularstudycanbe:generalizedtothelargerpopulationofinterest.replicatedwithdifferentsubjects,researchsettings,andtimeintervals.generalizedtoamorenaturalenvironment.ExternalValiditywhethertherAdvantagesofLabExperimentsSubjectsarerandomlyassignedtothetreatmentconditions–rulesoutselectionbias.Itisknownwhichvariablesareexogenousandwhichareendogenous–allowstomakecausalinferences.Doesmoneycauseoutputordoesoutputcausemoney?Experimentercanmanipulatechangesintheexogenousvariables–allowsfortheisolationoftruecauses.Manyvariablesthatcannotbedirectlyobservedinthefieldcanbeobservedinthelab.

Replicability–providesthebasisforstatisticaltests.Criticscanruntheirownexperiments.AdvantagesofLabExperimentsSObjectionstoLabExperimentsExternalvalidity:Canwegeneralizeourinferencesfromthelabtothefield?ObjectionstoLabExperimentsEFormillenniathesunriseseverymorning.Yet,thisdoesnotallowyoutomaketheinferencethattomorrowmorningthesunwillriseagain.Nevertheless,almostallpeoplebelievethis.Thisconfidenceistheessenceofinduction.Ifmanyexperimentshaveshownthat–givenacertainsetofconditions–robustandreplicableregularitiesemerge,wecanhavefaiththatthesameregularitieswilloccurinrealitygiventhattheconditionsaremet.Therefore,anhonestscepticwhodoubtstheexternalvalidityofanexperiment,hastoarguethattheexperimentdoesnotcaptureimportantconditionsthatprevailinreality.FormillenniathesunrisesevObjections–lackofrealismLabexperimentsareunrealisticandartificial.Mosteconomicmodelsareunrealisticinthesensethattheyleaveoutmanyaspectsofreality.However,thesimplicityofamodeloranexperimentisoftenavirtuebecauseitenhancesourunderstandingoftheinteractionofrelevantvariables.Thisisparticularlytrueatthebeginningofaresearchprocess.Whetherrealismisimportantdependsonthepurposeoftheexperiment.Oftenthepurposeistotestatheoryorunderstandingthefailureofatheory.Thentheevidenceisimportantfortheorybuildingbutnotforadirectunderstandingofreality.Objections–lackofrealismLaOtherObjectionsParticipantsarejuststudents–lackofrepresentativityThestakesaresmallThenumberofparticipantsissmallParticipantsareinexperiencedResponsesTakeothersubjectpools(workers,soldiers,CEOs)Conductrepresentativeexperiments(Fehretal.2003)Increasethestakes(CameronEI1999,Slonim&RothEctra1997,Fehretal.2002).Effectsarestronger.Increasethenumberofparticipants(IsaacandWalker,J.Pub.E1994)Inviteexperiencedparticipants(Kagel&Levin,AER1986).Effectsstillholdforexperiencedparticipants.OtherObjectionsParticipantsaInvestmentBehaviorandEmotionMyopicLossAversion(BenartziandThaler1995).Peoplepreferbondsoverstocks.Shivetal.(2005),PsychologicalScienceAllparticipantsweregiven$20ofplaymoneyandtheywouldreceiveagiftcertificatefortheamounttheywereleftwithattheendofthestudy.InvestmentBehaviorandEmotioInvestmentBehaviorandEmotion20roundsofinvestmentdecision.Oneachround,theyhadtodecidetoinvest$1.00ornotinvest.Iftheydecidednottoinvest,theywouldkeepthedollar.Iftheydecidedtoinvest,theywouldhandoveradollarbilltotheexperimenter.Theexperimenterwouldtossacoin.Iftheoutcomewereheads(50%),theparticipantlose$1;ifthetossweretails,thentheywin$2.50.Threegroupsofsubjects:Normalpeople,patientswithbraindamagesrelatedtoprocessingofemotions,patientswithbraindamagesnotrelatedtoemotions.InvestmentBehaviorandEmotioResultsResultsTargetPatients–average$25.70Normalpeople-$22.80ControlPatients-$20.07TargetPatients–average$25.前景理论ProspectTheory前景理论ProspectTheory产生背景传统经济学行为选择理论–冯。诺伊曼和摩根斯顿的最大期望效用理论(ExpectedUtilityTheory–VNM)EU=Σpiu(xi)u(xi)为效用函数，pi为事件发生的客观概率

RiskAversion(Concave)产生背景传统经济学行为选择理论–冯。诺伊曼和摩根斯顿的偏好公理占优性:决策者永远都会选择那些具有优势的策略。传递性:A>B，B>C，所以A>C独立性:决策者对两个策略的选择不受第三个不相干的策略影响。完全性:X优于Y或劣于Y或一样。偏好公理占优性:决策者永远都会选择那些具有优势的策略。阿莱斯悖论1988年诺贝尔经济学奖得主ALLAIS。1。下面两个选择，您更喜欢哪个呀？选择A：100%机会赢