The Hindsight Bias — Or, When We Think “We Knew It All Along”

The Hindsight Bias - Or, When We Think "We Knew It All Along" - Fallacy in Logic

Have you ever told someone that you knew the outcome of, say, a football game all along, after the game was already finished? If so, it is possible that your thinking was influenced by a cognitive mistake called hindsight bias.

It’s a type of cognitive bias — meaning an innate error in thinking shared by all of us — in which people perceive history as easier to predict than it really is. It affects people in a wide variety of situations and professions, hence it’s important to learn about it.

In this article, we’ll explain in more detail when it occurs and how it can stuff up your thinking.

Hindsight Bias

Hindsight bias, also known as the “knew-it-all-along phenomenon”, describes how people tend to view events that occurred in the past as more predictable than they really were.

As such, it may give one the false impression that they could have known with certainty what was going to happen, even if it was in fact impossible prior to the events taking place.

For example, this may occur in the following situations:

  • After attending a sports event, someone boasts that they knew all along how the game was going to turn out.
  • Post-election, someone asserts that they had predicted correctly who was going to get elected.
  • The weather gets cloudy in the afternoon and it starts raining. Someone says that “I felt it this morning that it’s going to rain later today”.

Furthermore, it is sometimes referred to as “creeping determinism”, indicating that it tends to creep on us without us being aware of it.

Why It Occurs

Hindsight bias is produced by two types of factors, cognitive and motivational:

  • Cognitive: Our human cognition, which is seen as the main contributor, may distort our memories of the actions we took or what we knew in the past in order for us to make better sense of things.
  • Motivational: We may be motivated to explain the history and different outcomes — especially when they were disadvantageous for us — in a way that is most desirable.


The Hindsight Bias - Or, When We Think "We Knew It All Along" - Fallacy in Logic

Baruch Fischhoff, an American academic, was the first to study and demonstrate the hindsight bias in the 1970s.

In one of his studies¹, the participating students were asked to guess the likelihood of different events that would follow from the US president Richard Nixon’s upcoming visits to China and the USSR. Some weeks to months after the president’s return, the researchers asked the students to point out the events had actually occurred and then recall the probabilities they had given earlier to each event.

As it turned out, the students overstated the likelihood they had given to the outcome that really happened and understated for those events that didn’t take place. In other words, their memories of their own predictions had been distorted in a way that’s more desirable for them.

In a similar experiment conducted by two researchers Dorothee Dietrich and Matthew Olson², the subjects predicted whether the U.S. Supreme Court nominee Clarence Thomas was going to be confirmed or not.

Before the vote took place, 58% of the subjects said that Thomas was going to be confirmed. This prediction turned out to be correct. Yet, in a new survey made after the result was known, a considerably higher number (78%) of the participants said they had predicted for a confirmation.

Hindsight Bias vs Outcome Bias

The hindsight bias is sometimes confused with the outcome bias, which describes the tendency to judge past decisions based on the results they produced.

However, the difference is that the former, unlike the latter, causes one to reach an inaccurate view of history due to a distortion in memory.


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