Paranormal Belief and the Conjunction Fallacy: Controlling for Temporal Relatedness and Potential Surprise Differentials in Component Events

Recent research suggests paranormal believers are especially prone to the conjunction fallacy'. The current study extends this work by presenting believers and non-believers with eight paranormal plus eight non-paranormal scenarios. Participants were given either a paranormal or virtually identical non-paranormal version of each scenario. Of these, half incorporated component events which were (virtually) co-occurring with half including components which were temporally disjointed. Analysis of Covariance (ANCOVA; controlling for gender and maths/stats/psychology qualifications) found believers made more conjunction errors than non-believers. Neither event type (paranormal vs. non-paranormal) nor components' temporal relationship (co-occurring vs. disjointed) had a significant effect on conjunction biases. Believers' tendency to produce larger conjunctive estimates was unrelated to group differences in component probability estimates (surprise values) and further, could not be attributed to group differences in the perceived functional relationship between component and conjunctive events. Possible explanations are discussed. Copyright (C) 2010 John Wiley & Sons, Ltd.