Hindsight bias, the tendency, upon learning an outcome of an event—such as an experiment, a sporting event, a military decision, or a political election—to overestimate one's ability to have foreseen the outcome. It is colloquially known as the “I knew it all along phenomenon.”

For example, people often believe that they could have predicted the outcome of a sports game after it has already been played. They may think that they could have predicted that a particular team would win, even though they had no way of knowing this before the game took place.

The bias is often observed in people's recall of events. For example, people may remember that they correctly predicted the outcome of an event, even if they did not actually do so. The hindsight bias can also be observed in people's judgments of events that have not yet happened. For example, people may think that they can predict the outcome of a future event,

People pretend as if they knew the guy could not fly a plane after a bad accident took place.