Availability Heuristic: Definition, Examples, & Bias

By Beth Birenbaum, MPH
​Reviewed by Tchiki Davis, M.A., Ph.D.
The availability heuristic is a mental shortcut we use to estimate probability and risk. It’s based on the belief that if we can remember an event easily, it must happen frequently. Let’s explore how this works and take a look at its benefits and pitfalls.
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Have you ever been afraid of something happening, even though a part of you knows it’s highly unlikely? 
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As a surfer, I’m in the ocean a lot. For many years, I never thought much about shark attacks—until one happened close to where I live and surf. As you might imagine, it was a big news story. Although I didn’t stop surfing, I found myself being more vigilant, looking around for danger signs. (Am I sure that was a dolphin?)
But if I’d thought about it logically, I would have realized the chances of being a victim of a shark attack were no greater than before. There wasn’t a higher number of sharks in the water, and the probability of an attack was (and is) still extremely small. Eventually, after some time with no further attacks or reported shark sightings, I stopped thinking about it. 

Shark attacks, plane crashes, terrorist attacks, and kidnappings are incredibly rare. Yet we often overestimate the frequency of these events which can trigger unnecessary worry. These errors in the perception of risk are often due to the availability heuristic. In this article, we’ll define the availability heuristic, look at some examples, and explain how it can set us up to make poor decisions.

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What Is The Availability Heuristic? (A Definition)

A heuristic is a mental shortcut or “rule of thumb” that helps us make judgments when information or time is limited (Tversky & Kahneman, 1974). The availability heuristic is a type of shortcut we use to assess the likelihood of an event. We base this assessment on how quickly and easily examples to mind. We believe that if we can remember something effortlessly, it must be important and happen frequently. It can be a useful tool for making quick judgments but can also lead us to poor decisions.

Video: What is Availability Bias | Explained in 2 Minutes

Theory Behind The Availability Heuristic

As described above, our minds are wired to intuitively believe that if something comes to mind easily, it must be true and common. But why do our brains work that way?

We make a lot of decisions every day. From simple things like what to wear to determining our likelihood of getting a specific disease. But the brain has limits on the amount of information it can process. So when a situation is complex, we often don’t have the capacity or the time to consider all the available information and possible alternatives. Heuristics simplify decisions by making the judgment process easier and more intuitive (Tversky & Kahneman, 1974). 

When it comes to determining risk when faced with uncertainty, our brains evolved to err on the side of overestimating danger. The ability to remember a tragic event quickly, and then take action to avoid a similar situation helped keep our ancestors safe. But it doesn’t always serve us well today. More on that next.​

Benefits & Pitfalls of The Availability Heuristic

Benefits:
The main benefit of the availability heuristic is it allows you to assess risk and make decisions quickly and easily (Pachur et al., 2012). As mentioned above, sometimes we just don’t have the time or resources to gather enough information to evaluate fully. The availability heuristic provides a foundation to draw conclusions fast, thus freeing up your mind to focus on other things. It simplifies complex decisions so you can take timely action. 

Another benefit is that simplifying the decision process reduces stress. It helps us avoid feeling overwhelmed by having too much to evaluate. So it’s needed in everyday life to navigate the world. But it can also lead us astray.

Pitfalls:
Ease of memory recall is often a poor guide for judging risk. Memories that are recent, unusual, or have an emotional component stand out. But this doesn’t necessarily mean these types of events happen frequently. So it’s easy to see how this can lead to bias, errors in judgment, and poor decisions. Here are a few examples of what can happen:

  • The availability heuristic can actually lead to riskier behavior. After 9/11, the fear of terrorist attacks persuaded many people to travel by car rather than flying, even though the odds of another similar attack were minuscule. This upsurge in car travel led to an increase in car crashes, causing almost as many deaths as the terrorist attack (Blalock et al., 2009). 
  • It can create unnecessary worry. If a friend was recently diagnosed with a serious illness, we tend to overestimate our chances of getting it too (Pachur et al., 2012). This can potentially increase worry and stress. And ironically, worry and stress can increase the risk of getting sick.
  • ​Miscalculating risk can hold you back from doing things you want to do like traveling or enjoying the ocean. What joyful life experiences might you be missing out on?

Examples of The Availability Heuristic

  • Fear of flying: An often cited example is overestimating the chances of being in a plane crash because of the extensive media coverage after one happens. This can trigger a fear of flying even though we’re far more likely to die in a car crash. 
  • Fear of terrorist attacks: This also stands out in our minds due to extensive media coverage and its emotional nature.
  • Fear of getting in the ocean after seeing the movie Jaws: It’s more common to die from being struck by lightning or be hit by parts falling off a plane.
  • Misjudging the incidence of diseases: When a health issue is highly publicized, we believe it happens a lot, and start to see it as an urgent health issue that needs attention. This can create an increase in public pressure to spend funds on research even though other diseases that are way more common get less funding or are ignored (Pachur et al., 2012).
  • Beliefs about global warming: In one study, participants ranked the seriousness of climate change higher if they were asked on a day that was unusually warm as opposed to unusually cold (Li et al., 2011).
  • ​Medical misdiagnosis: At the beginning of the Covid-19 pandemic, a case of Legionella pneumonia was mistakenly thought to be Covid (Kyere et al., 2022). This can be serious because it leads to inappropriate treatment.
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Here’s a personal example also related to Covid. When cases were surging, my husband had to fly due to a family emergency. The night after he returned, he woke up extremely dizzy and nauseous. He woke me up and stated confidently, “Bad news. I have Covid.” 

I didn’t remember dizziness being a symptom, but he managed to find some website that listed it (along with just about everything else). I wasn’t convinced, but clearly, something was wrong, so we went to urgent care. He was greeted by healthcare workers in full protective gear and ushered in to be examined. Ultimately, it was determined that he had vertigo, not Covid. But because Covid was all we heard about in those days, my husband gave this diagnosis more weight than it deserved. Only the negative Covid convinced him it was something else. ​

How Does The Availability Heuristic Create Bias?

The availability heuristic is also often called the availability bias. A bias is a feeling, inclination, or predisposition that is not based on reason or fact (dictionary.com, 2023). As you can see from the examples above, when we equate ease of recall with likelihood, we contribute to a belief that’s based more on emotion, intuition, or a feeling, rather than fact. While ease of recall can be a useful clue when assessing probability, this approach also leads to bias because it leaves out important factors that should be considered (Tversky & Kahneman, 1974).

How to Avoid The Availability Heuristic

Here are some tips to help avoid the availability heuristic:
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  • The first step is becoming aware of it. Ask yourself: Was this the first thing that popped into my mind? Is this memory emotionally charged or especially vivid? Is it something I saw recently in the news?
  • If possible, delay a decision.
  • Question your initial conclusions. Think about possible alternatives.
  • Get more information. Investigate using reliable sources. 
  • Listen to someone who holds the opposite belief.
  • Remember it’s okay to change your initial belief. Congratulate yourself on making a more informed conclusion!

​Video: Availability Bias: Learn to Overcome this Common Cognitive Bias

Availability Heuristic Questions

Here are some questions that people typically get wrong due to the availability heuristic:
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  • Which is a more dangerous job, police officer or logger? Answer: logger
  • In a group of 23 people, what are the chances 2 would share the same birthday? Answer: 50%
  • Are there more English words that begin with r or that have r as the third letter? Answer: the third letter (Tversky & Kahneman, 1974).
  • Which is more common in the United States, suicide or homicide? Answer: suicide

The Availability Heuristic & The Lottery

The availability heuristic explains why people buy lottery tickets even though the chance of winning is tiny. (The odds of winning Powerball are 1 in 292,201,338.) When someone does win, it’s highly publicized, and lottery companies play a large part in promoting awareness of the winners. They know it will be memorable and play on our emotions, using campaign slogans such as “It could be you!” We love to imagine ourselves in that situation. This entices us to make decisions based on a recent event (seeing a winner) and emotions rather than facts.

The Availability Heuristic vs Representative Heuristic

The representative heuristic is another shortcut to making decisions quickly. It’s often confused with the availability heuristic. But instead of assessing risk, we use it to judge whether something or someone belongs in a certain category. We make judgments about a person or object based on what we see as “typical”. How closely does someone or something match our image of what is representative? 

For example, if you meet someone who is quiet and reserved and dressed in a business suit, you might assume they’re an accountant rather than an actor. Like the availability heuristic, it feels intuitive and happens subconsciously. It’s pretty easy to see how this heuristic can contribute to stereotypes and can lead to incorrect evaluations.

The Availability Heuristic vs Anchoring Bias

Instead of basing judgments on how easy something is to remember, the anchoring bias uses the first piece of information we come across to make judgments. An example is your first impressions when meeting someone. Another is deciding the value of something based on the first price associated with it. We become “anchored” to the initial information and are resistant to adjusting beliefs away from it. 

Again, both of these heuristics are used to make decisions quickly. But the availability heuristic is used to determine likelihood, while anchoring is used for things like making numerical estimates, value estimations, or determining someone’s personality. 

In a marketing situation, a piece of information may be purposely given to you in an attempt to manipulate. A common example is when real estate brokers set the selling price of a home much higher than they expect to get. They know that buyers get anchored to that price. So when the seller comes down a little, the buyer feels like they’re getting a deal and are more likely to go for it.

The Availability Heuristic vs Confirmation Bias

Confirmation bias is our tendency to look for information that confirms our existing beliefs, and ignore or discount evidence that refutes it. We “cherry-pick” information or interpret information in a way that upholds what we already think. So unlike the availability heuristic, confirmation bias isn’t necessarily giving preference to things that come to mind easily. It involves a more active approach where we seek information that validates our current ideas. 

These two biases can also work together as explained in this video:

​Video: Availability Bias vs Confirmation Bias

Articles Related to The Availability Heuristic​

​Want to learn more? Check out these articles:

Books Related to The Availability Heuristic​

If you’d like to keep learning more, here are a few books that you might be interested in.

Final Thoughts on The Availability Heuristic

The availability heuristic can help us make fast and efficient decisions. It’s a useful and necessary tool when faced with uncertainty or when we don’t have time to evaluate more thoroughly. However, it also tends to cause us to overestimate risks which can hold us back from doing things we want to do. It can also drive us to make poor decisions.

Becoming aware of when we’re using the availability heuristic is the first step toward reducing its influence on us. The next time you hold back from doing something you want to do because it feels risky, you might ask how many people were not harmed by this activity. Or if it feels like you’re worrying a bit too much about something happening, it can help to do some research to find out if your fear is based on fact or emotion.

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