When reflecting on a past event, our perception is clouded by outcome knowledge—we know how things turned out. Hindsight bias describes how we project this current knowledge onto the past, making it difficult to remember the uncertainty we initially faced and distorting our memory of the thoughts, feelings, and knowledge we had at the time. This bias has interesting implications on an individual level, influencing how we judge past decisions—made by ourselves and others—and even shaping our predictions about the future.

Decision-making

The hindsight bias can have a negative influence on our decision-making. Part of what goes into making good decisions is realistically assessing their consequences. Suppose we look back at past decisions and conclude that their outcomes were indeed known to us at the time (when they weren’t). It makes sense that we will overestimate our ability to foresee the implications of our future decisions. This can be dangerous, as our overconfidence may lead us to take unnecessary risks.¹ Think of a gambler who looks back at past losses as predictable, making him increasingly confident that his next trip to the casino will be successful. Or consider an investor convinced that previous market crashes were entirely predictable, then overestimates their predictive abilities and takes on risky investments, confident they’ll be able to see the warning signs before another downturn.

Memory distortion

Hindsight bias can cause us to filter information from memory that contradicts the actual outcome of an event, like when we overlook all the good aspects of a relationship that ended badly or forget the early successes of a business that was “doomed to fail.” Interestingly, research suggests that we reconstruct our original memories using the outcome as a cue.¹¹ This is an unintended consequence of the brain’s efficient ability to select important information from our experiences to help us make sense of the world. However, selecting information from our memories based on event outcomes warps our understanding of the past and can alter our self-perception. We might judge ourselves harshly for failing to prepare for a situation that we “should have seen coming,” believing we tend to make poor choices due to our inherent inadequacy or incompetence. Research suggests that hindsight bias can also contribute to a “negative schema of the past,” where our knowledge base of past experiences is composed of negative outcomes believed to be foreseeable and inevitable, impacting our well-being and potentially playing a role in depression.¹²

Unfair judgments

While hindsight bias often colors our perception of our own decision-making skills, it can also cause us to judge others too harshly. We might be critical of people who failed to see signs that led to an undesirable outcome when we believe that a past chain of events was predictable. For example, if a colleague is fired, hindsight bias might lead us to believe they should have anticipated this outcome and worked harder to prevent it. 

A 2004 study on visual hindsight bias by Harley et al. demonstrates this well: Participants in the study identified blurred faces of celebrities as they gradually became clear, then were asked to recall at one point in the blurry-to-clear progression they could recognize the celebrity.¹³ Next, they were asked to recall the moment they personally recognized the celebrity, but also at what point a peer would be able to make the same recognition. The surprising outcome? Participants consistently overestimated their past abilities to identify celebrities and the performance of their peers. This study shows how hindsight bias can cause us to make unjust evaluations of other people’s decision-making abilities and place undue blame on others for any unfortunate outcomes they’re facing. As a result, we often assume that we would have made better choices if we were in someone else’s shoes and may even feel a sense of superiority over other people who fail to see the outcomes that we would have certainly predicted.

The hindsight bias can have troubling implications across different academic and professional areas where judging past decisions is critical to understanding the motivations behind certain behaviors or making risk assessments. It can also influence the public's perception of leaders and contribute to the systematic issue of victim blaming.

Judging past decisions

The accurate study of historical and political events may be tainted if researchers can’t put themselves in the shoes of decision-makers at that time—whose decisions weren’t informed by the foresight we have studying them today. This can cause details that seem obvious after the fact to be overlooked. Law, insurance, and finance are fields that all rely on realistic risk assessments based on similar past events, which the hindsight bias can distort. For example, research shows that hindsight bias can affect negligence judgments in criminal law cases, where judges with outcome knowledge perceive negative outcomes as significantly more foreseeable than those without this knowledge, leading them to believe that negligence was more often involved.¹⁴ Similarly, hindsight bias frequently contributes to victim blaming, which unfortunately can also influence legal outcomes—see our second example below for a more thorough look at this issue.

The hindsight bias happens when new information surrounding a past experience changes our recollection of that experience from an original thought into something different.² According to psychologists Neal Roese and Kathleen Vohs, there are three stacking levels of which this can occur.

The first level is “memory distortion.” This involves misremembering a past judgment or opinion. We often do this when claiming we said something when we didn’t. The second level is centered around our belief that a past event was inevitable. Roese and Vohs call this degree of the hindsight bias “inevitability.” The last level, “foreseeability,” entails believing that we could have foreseen the event.³ So, the bias occurs when we misremember our past thoughts, think a past event was inevitable, and subsequently, believe the event was foreseeable.

From their review of the existing literature, Roese and Vohs conclude that there are three main variables that affect the three levels of the hindsight bias to create our tendency to overestimate our predictive abilities:

1. Cognitive: We often distort our memory of past events by selectively remembering information that confirms what we now know to be true. This may be rooted in adaptive learning, which helps us update our understanding of the world and create a story that makes sense with the information we already have in what’s known as “sensemaking”. This is related to the confirmation bias.
2. Metacognitive: Metacognition is when we think about our thoughts themselves. When we find it easy to think and understand a past judgment or event, we might confuse ease with certainty. It is often easy to understand how or why an event happened in retrospect, due, at least in part, to the availability heuristic. This makes us certain that we had this understanding before.
3. Motivational: It brings us comfort to think that the world has order. This can motivate us to see unpredictable events as predictable. It also feels nice to think that your predictions were right or that you knew it all along even if you might not have. Research shows that our actions are often subconsciously motivated to promote a positive view of ourselves.^4,5

It is important that we are aware of the implications the hindsight bias can have on our lives. As mentioned earlier, this bias gets in the way by distorting the internal track-record we have of our past predictions. This can lead to overly confident future predictions that justify risky decisions with bad outcomes in both our personal and professional lives.

More broadly, the hindsight bias prevents us from learning from our experiences. If we already feel that we knew something all along, it is unlikely that we will carefully reflect on its outcome, and it will certainly prevent us from understanding why our predictions at the time might have been wrong. Ultimately, this can prevent us from understanding the true nature of an event or from identifying issues in how we make predictions.

One way that Roese and Vohs suggest counteracting the hindsight bias is to consider and explain how the outcomes that did not unfold could have unfolded. By mentally reviewing all the potential outcomes, an event will seem less inevitable and foreseeable. However, Roese and Vohs note that we should not look to consider an overwhelming number of alternative outcomes, as the decision-maker could misinterpret this difficulty as an indication of their implausibility rather than their sheer number.⁶

Another way of addressing dangerous overconfidence is to keep track of your past decisions and their associated predictions. This can be done in what’s known as a “decision journal,” which is similar to a diary but with details your decisions and what you were thinking when you made them.⁷ Having an unalterable track record of the predictions associated with your decisions (which will surely show some false predictions) might prevent the mistake of thinking you always knew it all along.

It’s also important to be aware of other biases that co-occur with hindsight bias. This knowledge will help you understand how various biases may impact your decision-making processes and influence your thinking. For example, negativity bias explains how we tend to pay more attention to the negative outcomes of events than positive ones. This means that when we look back on the past through the lens of hindsight bias, we might focus primarily on the predictability of negative consequences and generate an overly pessimistic view of our past decisions. Similarly, confirmation bias describes the tendency for people to interpret new evidence as confirmation of their existing beliefs. Suppose we believe that a particular decision was flawed because it led to a bad outcome. In that case, we might focus only on past evidence that supports this belief while overlooking information that might suggest our decision was reasonable at the time. As you can see, each of these distinct types of bias can interact with hindsight bias to further distort our perception of past events. Critical thinking strategies—like the suggestions above—can help counteract the effects of these biases and allow us to see the past and present more objectively. 

While the “knew-it-all-along” phenomenon is not new, its formal scientific study started in the early 1970s. Baruch Fischhoff was the first to study the hindsight bias experimentally, motivated by the seminal work of his supervisors, Daniel Kahneman and Amos Tversky, on heuristics. Fischhoff was also inspired by an article by Paul Meehl on doctors exaggerating their feeling of having known all along how their patient cases were going to turn out.

Interested in the phenomenon and its application to the predictability of political events in retrospect, Fischhoff joined with researcher Ruth Beyth-Marom to test his hypothesis in 1975. To do this, Fischhoff and Beyth-Marom asked participants to predict how likely the various outcomes to then U.S. President Nixon’s upcoming trip to China and the Soviet Union were.

Once Nixon had finished the trip, Fischhoff and Beyth-Marom asked participants to recall their initial predictions. The results showed that participants did not stick to the predictions they made before the trip, but instead gravitated towards the real outcomes of the trip. In other words, they recalled their predictions differently, favoring outcomes they knew were true in retrospect. This study inspired a broader scientific inquiry into the hindsight bias.⁸

When users reflect on their experiences with a digital product, the hindsight bias can lead them to believe that they predicted defects from the beginning—ranging from the layout not feeling quite right to the system frequently crashing. This certainty might skew users’ feedback, making it less about initial impressions or learning curves and more about their post-experience rationalizations. This bias can result in less constructive feedback, impacting the product's iterative improvement process.

In a similar way, hindsight bias can also influence people’s perceptions of product sustainability, an important purchase criterion in today’s eco-conscious market. A recent study found that consumers experience hindsight when confronted with surprising information suggesting that an unsustainable product is actually sustainable. Believing that they knew the product was really sustainable all along, these individuals were more likely to buy or recommend these products.¹⁷  The reverse also occurred: When consumers were confronted with negative information about a sustainable product, those who experienced hindsight bias were less likely to buy or recommend those products.

The authors of this study make a few helpful suggestions for marketers wanting to avoid or leverage hindsight bias. First, marketers should be mindful of how presenting consumers with unexpected information about a product can trigger hindsight bias. Marketers of sustainable products should use this insight to ensure consumers don’t encounter information that contradicts their initial expectations—like a product advertised as 100% biodegradable but arrives in a bunch of plastic packaging. Likewise, marketers have to be careful about making bold claims about sustainability if future information might come out that undermines these claims—like a Facebook post by an unhappy customer making accusations about greenwashing. On the other hand, marketers could intentionally trigger hindsight bias to enhance the appeal of unsustainable products, perhaps by highlighting aspects of the product that are less harmful to the environment than customers might initially believe.

After the outcomes of AI decisions are known, the hindsight bias can lead people to believe that they knew it all along, as if machine learning predictions are obvious or inevitable. This can lead to an overestimation of the AI's predictability and underestimation of its complexity, potentially causing overreliance on AI in critical decision-making situations.

Conversely, research suggests that overestimating our own abilities can lead to an under-reliance on AI systems, which could hinder progress in various sectors where AI could prove useful.¹⁶ This particular research explored the Dunning-Kruger Effect, which occurs when someone with limited competence in a certain area overestimates their skills. Hindsight bias might exacerbate the Dunning-Kruger Effect by making individuals believe they had more knowledge when facing past decisions than they really did and wrongly think they can make better decisions than AI based on this illusion of competence.

It is not uncommon to hear people claim that they predicted the outcome of political elections beforehand. Researchers Dorothee Dietrich and Matthew Olson conducted a study in 1993 to evaluate the extent to which voters alter their predictions following an election.

Dietrich and Olson asked 57 college students at Hamline University to predict how the U.S. Senate would vote on the confirmation of Supreme Court nominee Clarence Thomas. More specifically, participants were asked to predict the outcome of the vote, how it would be split between parties in the Senate, and to indicate how confident they were in their prediction. A month after the vote, participants were then asked to recall their predictions and level of confidence.⁹

The results supported the influence of the hindsight bias: before the Senate vote, 58% of students predicted that Thomas would be confirmed. But when students were questioned after the successful confirmation, 78% of them claimed that they had correctly predicted that Thomas would be approved.¹⁰

In both the court of law and public opinion, the hindsight bias may play a role in “victim-blaming.” As mentioned above, part of the reason why this bias arises is that we often look for the easiest explanations and predictions in order to quickly make sense of the world. It is easier to focus on individuals and their actions over more nuanced, systemic causes. It is also easy to form and support predictions for events that have already occurred.

This may explain the prevalence of victim-blaming in cases involving sexual assault. Victims or survivors of such cases are often blamed for their affliction using the rationale “they should have known better” in retrospect. Indeed, studies have shown that this bias contributes to victim derogation in rape cases.

What it is

The hindsight bias describes our tendency to look back at an event that we could not predict at the time and think the outcome was easily predictable. It is also called the “knew-it-all-along” effect.

Why it happens

First, we often distort our memory of past events by selectively remembering information that confirms what we already know to be true. This is done to create a story that makes sense with the information we already have in what’s known as “sensemaking.” 

Second, when people find it easy to think and understand a past judgment or event, they can confuse ease with certainty. It is often easy to understand how or why an event happened in retrospect. This makes us certain that it is an understanding we had before.

Third, it brings us comfort to think that the world is orderly. This can motivate us to see unpredictable events as predictable. It feels good to think that you knew it all along even if you might not have.

Example #1 - Political predictions

A 1993 study asking college students to predict how the U.S. Senate would vote on the confirmation of a Supreme Court nominee supported the influence of the hindsight bias. Before the Senate vote, 58% of students predicted that Thomas would be confirmed. But when students were questioned after the successful confirmation, 78% of them claimed that they originally thought Thomas would be approved.

Example #2 - Blaming victims

The hindsight bias may have a role to play in the victim blaming prevalent in sexual assault cases, since people believe survivors should have “known better” in retrospect. Research suggests that hindsight bias contributes to victim derogation in rape cases.

How to avoid it

One way to avoid the hindsight bias is to consider and explain how the outcomes that did not unfold could have unfolded. By mentally reviewing all the potential outcomes, an event will seem less inevitable and foreseeable.

Another strategy is to keep track of your past decisions and their associated predictions. Having an explicit and unalterable track record of the predictions associated with your decisions (which will surely show some false predictions) might prevent the mistake of thinking you always knew it all along.

“If Only”: The Good and the Bad of Counterfactuals

In this article, staff writer Kaylee Somerville breaks down the pros and cons of counterfactuals: thoughts about how past scenarios could have gone differently. Somerville explains that when left unchecked, counterfactual thinking can lead us to fall victim to biases such as the hindsight bias.