Is there hindsight bias without real hindsight? Conjectures are sufficient to elicit hindsight bias.

After learning about an event, people often mistakenly believe to have predicted what happened all along (hindsight bias). However, what if what has happened is not known, but subject to conjecture? Could conjectures, in the absence of knowledge about the event, elicit the same bias and make people believe they “conjectured it all along”, too? We examined this question in 2 studies. Immediately after the disappearance of flight MH370 in March, 2014, we asked N = 432 individuals about the likelihood of a number of possible events. One year later, N = 100 of these individuals participated again and were randomly assigned to 2 experimental conditions. Participants in the current conjecture group answered the same questions from their current perspective, participants in the reproduced conjecture group were asked to reproduce their earlier estimates. Results show that conjectures had changed over time and affected participants’ reproductions of their earlier estimates. We replicated this finding in a controlled lab experiment (N = 94) and found a comparable magnitude of conjecture-based and knowledge-based hindsight bias. These findings demonstrate hindsight distortions in the absence of definite knowledge and extend theoretical assumptions about the prerequisites of hindsight bias in the context of events. (PsycINFO Database Record (c) 2019 APA, all rights reserved)