Availability Bias

It’s winter in the UK, and flu season is upon us. I saw a really sick kid a few days ago and admitted him to hospital. He’d been seen just a few days before with what looked like a simple cold. Now he’s on a paediatric ward with pneumonia, struggling to breathe, parents terrified out of their minds.

The trouble is, now every time I see a kid with a snotty nose, I’m even more worried they’re going to end up in hospital too. I’m overreacting. I know I’m overreacting. But I can’t help it. The image of that sick child is so fresh, so vivid in my mind that it’s affecting every clinical decision I make.

This is availability bias at work, and it’s messing with my judgment in exactly the way it’s probably messing with yours.

How Your Brain Tricks You With Examples

Availability bias is what happens when you judge the probability of something based on how easily you can recall examples of it happening. The more vivid the memory, the more available it is, the more likely you think that event is to occur. Your brain uses mental shortcuts to make quick decisions, and one of those shortcuts is “if I can think of it easily, it must be common.”

This works brilliantly for actual threats. If you can easily remember people being mauled by tigers, you’re appropriately cautious around tigers. The problem is that your brain applies this same logic to everything, including things where your available examples are completely skewed.

Memories and events that can easily be recalled really affect the way you judge probability. You see lottery winners on the front page of newspapers, so you think it’s more likely you’re going to win. Using this logic, you buy more lottery tickets. You’ve seen it work for someone, right? It’s vivid. It’s available. It must be possible for you too.

Except the odds haven’t changed. They’re still millions to one against you. But your brain doesn’t process statistics. It processes stories. And the story of the lottery winner is far more available than the story of the millions who didn’t win.

Sensationalised news sells newspapers. You already know this. But have you ever taken the time to consider that this sensationalised news is also giving you distorted available examples that really affect how you make decisions? The news doesn’t report on the thousands of flights that landed safely today. It reports on the one that crashed. So you think crashes are more common than they are.

The Probability You’re Getting It Wrong

We tend to judge probability by how quickly and easily we can think of examples of that event happening. This is availability bias at work, and it’s causing you to make terrible decisions.

It’s not that likely that you’re going to die in a plane crash, despite the fact that when a crash does happen, it’s plastered all over the newspapers for weeks. The actual odds of death by plane crash are approximately eleven million to one. You’re more likely to die driving to the airport than on the flight itself. But due to availability bias, you judge the probability of a crash to be much higher than it actually is, and it fuels your anxiety.

I had a patient who refused to fly. Absolutely refused. She’d drive twelve hours rather than take a two-hour flight. She had vivid memories of watching news coverage of plane crashes. She could recall every detail of the wreckage, the survivors being interviewed, the investigators picking through debris. Those memories were so available, so easy to access, that flying felt impossibly dangerous to her.

Meanwhile, she thought nothing of driving at seventy miles per hour in the rain and heavy traffic. Because car accidents, while statistically far more likely, didn’t have the same vivid, dramatic availability in her mind. She’d been in minor car accidents before. They weren’t that bad. She was fine.

That’s availability bias making her judgment completely backwards.

The Internet Makes It Worse

The trouble is we’re guilty of making our decisions based on bad press, bad research, and even on the “what ifs” of something that hasn’t even happened, something our own catastrophic thinking has imagined. Sometimes it’s easier to bring to mind an available example, real or unreal, than to think logically about the problem itself.

Frightening or sensationalised events are easily brought to mind. Go online and you’ll find no shortage of people blogging and ranting about their complaints, woes, and problems. Increasingly now, with social media, polarised or sensationalised views are even more likely to be shared than any rational argument or comment.

Parents are more likely to believe the worries of other parents on internet forums when it comes to vaccinations rather than the rational view of the medical establishment, who base their thinking on actual data. Why? Because a parent’s passionate story about their child having a reaction is far more vivid, far more emotionally compelling, far more available than a dry statistical analysis showing vaccinations are safer than the diseases they protect against.

One dramatic story beats a thousand boring statistics every single time in your brain’s assessment of risk.

When Lack of Availability Blinds You

Availability bias doesn’t just make you overestimate risks. It can also make you underestimate them. Malaria kills more than half a million people per year. But most people in this country haven’t been affected by malaria. They don’t have vivid memories of people dying from it. They can’t easily recall examples. So they judge that catching malaria isn’t really likely to happen to them.

Then they travel to endemic areas without taking simple precautions. No antimalarial medication. No mosquito nets. Because the risk doesn’t feel real. It’s not available in their memory, so their brain files it under “not a real threat.”

That’s the availability heuristic working in reverse. The lack of available examples makes you think something’s less likely than it actually is.

I see this with smoking constantly. People tell me their grandfather smoked every day of his life and lived to ninety-nine. That one vivid example, that one available story, completely overrides all the statistics about smoking-related deaths. Because Grandad is more available to them than the abstract concept of smoking-related mortality.

So they keep smoking. Because in their available examples, smoking doesn’t kill you. Getting hit by a bus at ninety-nine kills you. The fact that around one in six deaths in the UK is linked to smoking doesn’t compute. It’s not available. It’s not vivid. It’s just numbers.

How It Keeps You Stuck

Availability bias stops you thinking rationally, logically, and in line with actual probability. If you have a strong memory of failing at something, then you feel it’s more likely you’re going to fail again. So you don’t even try. Success gets further and further away, and mentally you’re just reconfirming this bias even more.

You failed once. It was embarrassing. It was painful. The memory is vivid. So now every time you think about trying again, that failure pops right up, front and centre in your mind. Your brain says “See? This is what happens when you try. Remember how bad it felt? Let’s not do that again.”

Never mind that you’ve succeeded at dozens of other things. Never mind that one failure doesn’t predict future failure. That one vivid memory is so available that it drowns out everything else.

The Third Letter Problem

Here’s a quick test. What’s more common: words beginning with the letter R, or words with R as their third letter?

It’s easier to recall words beginning with the letter R, so that’s probably what you initially think. Restaurant. Rabbit. River. Red. They come to mind quickly. But in fact, there are roughly three times as many words with R in third position as there are words that begin with it.

Your brain just can’t easily generate examples of words with R as the third letter, so it assumes they’re less common. That’s availability bias in its purest form. The ease of recall determines your judgment of frequency, completely independent of actual frequency.

The Bad Events You Can’t Forget

It’s also easier to recall bad events or traumatic events from your past. These are strong memories. They’re emotionally charged. They’re seared into your brain. These tend to be the events that cloud your judgment for the future and affect your decision-making.

You were rejected once in a humiliating way. That memory is available. Vivid. Painful. So now you assume rejection is likely, even probable. You don’t ask for what you want. You don’t put yourself out there. Because your brain is constantly serving up that one awful memory as evidence that this is what happens when you try.

Meanwhile, the dozens of times things went fine, the times you weren’t rejected, the times people said yes? Those memories are less dramatic. Less emotionally charged. Less available. So they don’t factor into your risk assessment at all.

Making Better Decisions

Ask yourself why you’re making the decisions you’re making. Are your decisions based on examples you can easily recall rather than fact and rational thought? Are you basing your decision to take action or not to take action on the availability of memories or examples from your past?

Even worse, some people judge what they do and don’t do based on their own catastrophic thinking about what could go wrong, even when it hasn’t happened, rather than what’s most likely to happen. They’re making decisions based on imagined available examples. Not even real ones. Just vivid scenarios they’ve constructed in their own minds.

Availability bias really affects the decisions you make in life. The solution is to try and catch yourself thinking of these strong memories when you’re making decisions. Are these memories and examples influencing your decisions going forward? Learn from the past, but don’t let it dictate your future.

When you’re assessing risk, when you’re deciding whether to try something, when you’re judging how likely something is to happen, stop and ask yourself: am I basing this on actual probability, or am I basing this on how easily I can recall examples?

Because your brain is lying to you. It’s using mental shortcuts that worked brilliantly when we were avoiding predators on the savannah, but work terribly when we’re making complex decisions in the modern world.

Don’t let the most vivid memory in your head determine your entire future. That’s not wisdom. That’s just availability bias doing its thing.

Further reading

• Tversky, A., & Kahneman, D. (1973). Availability: A heuristic for judging frequency and probability. Cognitive Psychology, 5(2), 207-232.
• Kahneman, D. (2011). Thinking, Fast and Slow. Farrar, Straus and Giroux.
• Slovic, P. (1987). Perception of risk. Science, 236(4799), 280-285.
• Lichtenstein, S., Slovic, P., Fischhoff, B., Layman, M., & Combs, B. (1978). Judged frequency of lethal events. Journal of Experimental Psychology: Human Learning and Memory, 4(6), 551-578.
• Gigerenzer, G. (2004). Dread risk, September 11, and fatal traffic accidents. Psychological Science, 15(4), 286-287.
• Schwarz, N., Bless, H., Strack, F., Klumpp, G., Rittenauer-Schatka, H., & Simons, A. (1991). Ease of retrieval as information. Journal of Personality and Social Psychology, 61(2), 195-202.
• Tversky, A., & Kahneman, D. (1974). Judgment under uncertainty: Heuristics and biases. Science, 185(4157), 1124-1131.
• Ariely, D. (2008). Predictably Irrational. HarperCollins.
• Gilovich, T. (1991). How We Know What Isn’t So. Free Press.
• Thaler, R. H., & Sunstein, C. R. (2008). Nudge. Yale University Press.