Post hoc illusion—how the knew-it-all-along effect undermines trust

This article introduces a theory of distrust called the post hoc illusion. The post hoc illusion is a mistaken belief about what others knew in the past. It arises when stakeholders, who have entrusted power to the deciders, infer that the decider “overlooked” facts that were “obvious” and should have been consulted. We show how this effect is a logical consequence of constraints in human abductive processes–the manner in which human minds create and evaluate causal explanations. A research agenda for the post hoc illusion is then proposed, beginning with the identification of key variables that should influence its operation: relevant facts present in the past and theoretical novelty. We then argue that the illusion can be ameliorated through narratives that portray the decider’s state of mind in the past.