Hindsight Bias

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Hindsight bias, which some psychologists refer to as “I knew that was going to happen” effect, is a psychological phenomenon in which people exaggerate the predictability of an event after it has already happened.


Why should I be aware of this?

Hindsight bias actually helps people think more clearly sometimes, by helping the brain to retain correct and relevant information rather than incorrect information, according to a study performed by the American Psychological Association in 2000.

According to new research, hindsight bias is actually a by-product of a cognitive mechanism that allows us to unclutter our minds by discarding inaccurate information and embracing that which is correct.

Psychologists, however, call hindsight bias one of the most systematic errors in human perception. Across a wide spectrum of issues, from politics to the vagaries of the stock market, experiments show that once people know something, they readily believe they knew it all along.

All about Hindsight Bias

A study conducted by the American Psychological Association in 2000 came to the conclusion that hindsight bias actually helped people think more clearly sometimes, by enabling the brain to retain correct and relevant information rather than incorrect information.

It is necessary to give due importance to hindsight bias in criminal cases, because a witness may not be strictly accurate as he or she may be influenced by hindsight bias, along with a number of other biases which can influence the way someone's brain restores and recalls information.

Along with several other biases documented in psychology, the hindsight bias is caused by something known as availability heuristic. Essentially, people make assessments about things on the basis of information which they can bring readily to mind, although this may not be the most scientific way to base such an assessment. In the case of hindsight bias, people turn a few vague statements into solid predictions, and assume that an event like the outcome of a Presidential election is predictable on the basis of their experiences.

A form of comfort

Hindsight bias seems to offer a form of comfort. It is easy to be confident about the past, because one cannot be proved wrong. Once something happens, we scan the past for proof as to how that event happened, while ignoring all the factors that could have led to different outcomes.


  • After Europe introduced a common currency, one experiment documented the hindsight bias of volunteers in Austria. They were asked, six months ahead of time, to guess how the change would affect them, and then to remember what they had guessed six months after the changeover. Large numbers of people revised their recollections to match what had actually happened in the interim.
  • Other studies have found that once jurors hear information, asking them to disregard it is often useless. Once you know something, the hindsight bias makes it very difficult to put yourself back in the shoes of the person who did not know that piece of information.
  • In yet another experiment, Baruch Fischhoff, a psychologist at Carnegie Mellon University and a pioneer in the field of hindsight bias, found that Americans who made estimates about their danger after the Sept. 11, 2001, attacks recalled having made much lower estimates of risk a year later, after their fears failed to materialize. [1]

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Additional information


  • What is Hindsight Bias?
  • Iraq War Naysayers May Have Hindsight Bias


  1. Washington Post