Proceedings of the Annual Meeting of the Cognitive Science Society

Illusory causation is a consistent error in human learning inwhich people perceive two unrelated events as being causallyrelated. Causal illusions are greatly increased when the targetoutcome occurs frequently rather than rarely, a characteristicknown as the outcome density bias. Unlike most experimentaldesigns using binary outcomes, real-world problems to whichillusory causation is most applicable (e.g. beliefs aboutineffective health therapies) involve continuous and variableconsequences that are not readily classifiable as the presenceor absence of a salient event. This study used a causallearning task framed as a medical trial to investigate whetheroutcome density effects emerged when using a continuousand variable outcome that appeared on every trial.Experiment 1 compared the effects of using fixed outcomevalues (i.e. consistent low and high magnitudes) versusvariable outcome values (i.e. low and high magnitudesvarying around two means in a bimodal distribution).Experiment 2 compared positively skewed (low density) andnegatively skewed (high density) continuous distributions.These conditions yielded comparable outcome density effects,providing empirical support for the relevance of the outcomedensity bias to real-world situations in which outcomes arenot binary but occur to differing degrees.