What Is a Hindsight Bias?

Hindsight bias
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They say that hindsight is 20/20. In other words, things always seem more obvious and predictable after they have already happened. Learn more about how the hindsight bias can influence your beliefs and decisions.

What Exactly Is the Hindsight Bias?

  • The term hindsight bias refers to the tendency people have to view events as more predictable than they really are.
  • After an event, people often believe that they knew the outcome of the event before it actually happened.
  • The phenomenon has been demonstrated in a number of different situations, including politics and sporting events. In experiments, people often recall their predictions before the event as much stronger than they actually were.

Examples of the Hindsight Bias

For example, researchers Martin Bolt and John Brink (1991) asked college students to predict how the U.S. Senate would vote on the confirmation of Supreme Court nominee Clarence Thomas. Prior to the senate vote, 58-percent of the participants predicted that he would be confirmed. When students were polled again after Thomas was confirmed, 78-percent of the participants said that they thought Thomas would be approved.

The hindsight bias is often referred to as the "I-knew-it-all-along phenomenon." It involves the tendency people have to assume that they knew the outcome of an event after the outcome has already been determined. For example, after attending a baseball game, you might insist that you knew that the winning team was going to win beforehand.

As a psychology student, you may have also experienced the hindsight bias in your own studies. As you read your course texts, the information may seem easy. "Of course," you might think after reading the results of a study or experiment. "I knew that all along."

This can be a dangerous habit for students to fall into, however, particularly when test time approaches.

By assuming that you already knew the information, you might fail to adequately study the test materials.

When it comes to test time, however, the presence of many different answers on a multiple choice test may make you realize that you did not know the material quite as well as you thought you did. By being aware of this problem, you can develop good study habits to overcome the tendency to assume that you 'knew-it-all-along.'

Explanations for the Hindsight Bias

So what exactly causes this bias to happen?

Researchers suggest that three key variables interact to contribute to this tendency to see things as more predictable than they really are.

  1. First, people tend to distort or even misremember their earlier predictions about an event. As we look back on our earlier predictions, we tend to believe that we really did know the answer all along.
  2. Second, people have a tendency to view events as inevitable. When assessing something that has happened, we tend to assume that it was something that was simply bound to occur.
  1. Finally, people also tend to assume that they could have foreseen certain events.

When all three of these factors occur readily in a situation, the hindsight bias is more likely to occur. When a movie reaches its end and we discover who the killer really was, we might look back on our memory of the film and misremember our initial impressions of the guilty character. We might also look at all the situations and secondary characters and believe that given these variables, it was clear what was going to happen. You might walk away from the film thinking that you knew it all along, but the reality is that you probably didn't.

More Cognitive Biases


Myers, David G. (2005). Social psychology (8 ed.). McGraw-Hill Education. pp. 18–19.

Roese, N.J., & Vohs, K.D. (2012). Hindsight bias. Perspectives on Psychological Science, 7(5), 411-426.

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