Proceedings of the Annual Meeting of the Cognitive Science Society

In a causal illusion task, participants rate a cue that has an objectively null contingency with an outcome as causal. Trials are usually organized according to a 2x2 table representing the presence/absence of a binary cue and a binary outcome. Cell A outcomes (cue, outcome) can be attributed to the cue. But how do participants interpret trials from cell C (no cue, outcome), where the cause of the outcome is unspecified? In two experiments we asked participants to provide causal explanations for cell A and C trials in a medicine-recovery causal illusion task. Participants who reported that the cause of cell C outcomes (e.g., strong immunity, spontaneous recovery) did not also apply to cell A outcomes showed the strongest causal illusion. Such a causal reasoning process undermines the logic behind the delta P metric typically used to define a contingency, and thereby provides a potential normative account of causal “illusions”.