Coincidence judgment in causal reasoning: How coincidental is this?

Given the important conceptual connections between cause and coincidence as well as the extensive prior research on causality asking, "how causal is this?", the present research proposes and evaluated a psychological construction of coincidentality as the answer to the question, "how coincidental is this?" Four experiments measured the judgment properties of a reasonably large set of real coincidences from an initial diary study. These judgements included coincidentality and an array of other judgments about event uncertainty, hypothesis belief and surprise as predictors of coincidentality consistent with and supporting our prior definition of coincidence (Johansen & Osman, 2015): "coincidences are surprising pattern repetitions that are observed to be unlikely by chance but are nonetheless ascribed to chance since the search for causal mechanisms has not produced anything more plausible than mere chance." In particular, we evaluated formal models based on judgements of uncertainty, belief and surprise as predictors to develop a model of coincidentality. Ultimately, we argue that coincidentality is a marker for causal suspicion/discovery in terms of a flag that a new, unknown causal mechanism may be operating.