Proceedings of the Annual Meeting of the Cognitive Science Society

Decision makers often reject mixed gambles offering equalprobabilities of a larger gain and a smaller loss. This importantbehavioral pattern is generally seen as evidence for lossaversion, a psychological mechanism according to whichlosses are given higher utility weights than gains. In this paperwe consider an alternate mechanism capable of generatinghigh rejection rates: A predecisional bias towards rejectionwithout the calculation of utility. We use a drift diffusionmodel of decision making to simultaneously specify and testfor the effects of these two psychological mechanisms in agambling task. Our results indicate that high rejection rates formixed gambles result from multiple different psychologicalmechanisms, and that a predecisional bias applied prior to thecomputation of utility (rather than loss aversion) is the primarydeterminant of this important behavioral tendency.