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1、ABayesianComparisonofChoiceStrategiesUnderAleatoryandEpistemicUncertaintyGordonF.PitzUniversityofNorthCarolina,ChapelHillandThomasS.WallstenUniversityofMaryland,CollegeParkPsychonomicSocietyAnnualMeetingNewOrleansNovember18,2000Aspointedoutbyseveralauthors(e
2、.g.,Howell&Burnett,1978;Kahneman&Tversky,1982),uncertaintyinachoicetaskcantaketwoforms.Aleatory(orexternal)uncertaintyreflectsourdirectexperiencewitheventsthatvary.Forexample,alonghistoryofmeetingadultmenandwomenhasgivenmesomesenseoftheaverageheightsforeachs
3、exandthevariabilitythatcanoccur.Epistemic(orinternal)uncertaintyreflectsthepossibilityoferrorsinourgeneralknowledge.Forexample,IbelievethatthepopulationofLouisianaislessthanthepopulationofMissouri,butI'mnotsureofthat.Weusesignaldetectiontheory(SDT)asausefulm
4、ethodfordescribingchoicebehaviorintasksthatinvolveeitheraleatoryorepistemicuncertainty.Assumethatadecisionmakermakesabinarychoice,andgivesaconfidenceratinginthatchoice.AccordingtoSDT,thedecisionmakergives,say,a"ConfidentYes"responseifanobservationonsomeunder
5、lyingdimensionexceedsafixedcriterion(Figure1).Iftherearefourpossibleresponsestheremustbethreecriteria.Thelocationofthesecriteriacanreadilybeestimatedfromobservedresponseproportions.Considerthe"ConfidentYes"criterioninFigure1.Wecanimagineatleastthreestrategie
6、sthatadecisionmakermightuseinsettingthecriterion.InclassicSDTitisdeterminedbythelikelihoodratio,i.e.,theratioofthetwoordinatesatthecriterion.Itisalsopossiblethatthecriterionisdeterminedbyitsdistancefromoneofthetwodistributionmeans(orfromtheaverageofthetwomea
7、ns),orbytheresponseprobabilitythatitestablishes,inthiscasetheprobabilityofa"ConfidentYes"response.Inasingletaskdomainwehavenoideawhichofthesestrategies,ifany,leadstotheobservedcriterion.However,ifweuseseveraldomainswithvaryingd'values,andifthedecisionmaker's
8、strategyremainsthesame,thethreestrategiescanbedistinguished.Figure2showshow"ConfidentYes"criterionwouldchangeifd'increaseswhileeitherthelikelihoodratio,distance,orresponseproportionremainfixed.I
