Illusory causation and outcome density effects with a continuous and variable outcome

AbstractIllusory causation represents a consistent error in human learning. It is a bias that causes people to perceive two unrelated events as causally associated with one another. These causal illusions are greatly increased when the target outcome occurs frequently rather than rarely, a characteristic known as the outcome density bias. Unlike most experimental designs using binary outcomes, real-world problems to which illusory causation is most applicable (e.g. beliefs about ineffective health therapies) involve continuous and variable consequences that are not readily classifiable as the presence or absence of a salient event. This study used a causal learning task framed as a medical trial to investigate whether similar outcome density effects emerged when using a continuous and variable outcome that appeared on every trial. Experiment 1 compared the effects of using fixed outcome values (i.e. consistent values for low and high magnitude) versus variable outcome values (i.e. low and high magnitudes varying around two means in a bimodal distribution). Experiment 2 compared positively skewed (low density) and negatively skewed (high density) continuous distributions. These conditions yielded comparable outcome density effects, providing empirical support for the relevance of the outcome density bias to real-world situations in which outcomes are not binary but occur to differing degrees.


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