Cognitive Bias

I. Definition

A cognitive bias is a bad mental habit. It’s a way of thinking that might be very common and, on its surface, might even appear rational – but in fact it gets in the way of logical thinking.

For example, if all of your friends believe something, you’re much more likely to believe it as well. That’s not a very rational basis for believing something, but it is something that almost everyone experiences at some point, and it’s a mistake that many people will repeat over and over again in different situations. In philosophy and cognitive science, this error is called “bandwagoning,” and it’s one of the most well-known cognitive biases.

What you consider a “cognitive bias” depends on what your standards of reasoning are. No one is capable of complete rationality – we have to make decisions all the time based on limited information, and we use instinct, emotions, and prior teachings as a guide. There’s nothing wrong with that. But we all have certain standards or guides that help us think logically– not making big decisions while angry or tired, for example. Cognitive biases are the mental tendencies that prevent us from living up to those standards and being completely rational.

While this article lists some basic cognitive biases that have been observed by philosophers and behavior scientists, it’s a long way from a complete list – there are literally thousands of cognitive biases out there. Depending on your standards of rationality, different kinds of mental habits will count as obstacles to that rationality, and this will determine your list of cognitive bias.

The lists will also vary because not everyone’s brain works in the same way. Your brain has its own particular habits of thought, and they’re different from everyone else’s. That means there may be cognitive biases that other people suffer from but you don’t, while your own biases may or may not be shared by others.

Cognitive biases are closely related to logical fallacies, but cognitive biases exist in a mind whereas logical fallacies exist in an argument. One way to think of it would be that when you read a faulty argument, you may fall for its fallacies because your cognitive biases are clouding your vision.


II. Types of Cognitive Bias

There are hundreds of cognitive biases out there – way more than we could ever explore in a short article. This list includes just 10, chosen because they are either especially common or especially interesting.

Anchoring BiasTendency to focus too much on a single piece of information rather than all available information; this usually happens with either the first piece of information you received, the most recent information you received, or the most emotional information you received.
Availability HeuristicTendency to attach too much weight to information that we happen to have available to us, even if we’ve done no systematic research. For example, people tend to believe that their personal anecdotes are evidence for how the world works. If your cousin’s child developed autism after going through a standard round of vaccinations, you may believe that vaccinations cause autism even though science has conclusively shown that they don’t.
BandwagoningTendency to adopt the same beliefs as the people around you, or to assume that other people are making the right decision. If you live in a city with a subway, you may have seen bandwagoning at work – sometimes, a long line will form at one turnstile while the one next to it is completely free. Each new person shows up and just assumes that the second turnstile is broken, or else why would there be this disparity in the lines? But if no one decides to test this assumption, then the line will get longer and longer for no good reason!
Confirmation BiasOne of the most important cognitive biases! This is a tendency to find evidence that supports what you already believe – or to interpret the evidence as supporting what you already believe. Changing your viewpoint is hard cognitive work, and our brains have a tendency to avoid doing it whenever possible, even when the evidence is stacked against us!
Dunning-Krueger EffectLess competent people have a tendency to believe that they know more than they actually do. Well-informed people usually have very low confidence in their own views, because they know enough to realize how complicated the world is. People that are not well informed are extremely confident that their views are correct, because they haven’t learned enough to see the problems with those views. This is what Socrates meant when he said that true wisdom was “to know that I know nothing.”
Fundamental Attribution ErrorThe tendency to believe that your own successes are due to effort and innate talent, while others’ successes are due to luck. Conversely, it’s also the tendency to believe that your own failures are due to bad luck, while other people’s failures are due to lack of effort and talent. Basically it means you give yourself credit while denying credit to others. This bias has broad effects in cross-cultural encounters.
Halo EffectTendency to perceive a person’s attributes as covering more areas than they actually do. For example, if we know that a person has one type of intelligence (good at math, say) we tend to expect that they will show other kinds of intelligence as well (e.g. knowledge of history).
Mood-Congruent Memory BiasTendency to recall information that fits our current mood, or to interpret memories through that lens. When in a foul mood, we easily recall bad memories and interpret neutral memories as though they were bad. Leads to a tendency to think that the world is a sad, happy, or angry place when really it is only our mood.
Outcome BiasTendency to evaluate a choice on the basis of its outcome rather than on the basis of what information was available at the time. For example, a family may decide to send their child to an expensive college based on good financial information available at the time. However, if the family later falls into financial hardship due to unforeseen circumstances, this decision will appear, in retrospect, to have been excessively risky and a bad choice overall.
Pro-Innovation or Anti-Innovation BiasTendency to believe something is good (or bad) simply because it’s new. In Western society we tend to overvalue innovation, while other societies (and many sub-cultures within the West, such as religious fundamentalists) overvalue tradition. Both biases are irrational: just because something is new or old doesn’t mean it’s going to be more or less beneficial. When we evaluate ideas, we should do it on the basis of their own merits, not simply how new or old the idea is.


III. Quotes About Cognitive Biases

Quote 1

“Where all think alike there is little danger of innovation.” (Edward Abbey)

There are actually two cognitive biases that you can see in this short quotation. On the surface, it’s about bandwagoning: people’s tendency to adopt the opinions of the people around them. But Abbey sarcastically criticizes bandwagoning by pointing out that it’s bad for innovation – if something is bad for innovation, he implies, then that means it’s bad overall. But that would only be true if innovation was inherently good! Thus, in critiquing one cognitive bias (bandwagoning), Abbey falls into another one (pro-innovation bias).

Quote 2

“Most of us are not really approaching the subject [the Bible] in order to find out what Christianity says: we are approaching it in the hope of finding support from Christianity for the views of our own party.” (C.S. Lewis)

C.S. Lewis, who wrote The Chronicles of Narnia, was also a philosopher and scholar of Christianity. In this quote, he warns about the dangers of confirmation bias in a religious context – in reading scriptures, he says, too many people simply hunt around for evidence to support whatever views they already hold, rather than keeping an open mind and trying to learn something new. This is equally true (perhaps more so) for people who read scriptures from other faiths – they often look around for evidence of what’s wrong with those faiths rather than trying to get an accurate understanding of what the book is actually saying.


IV. The History and Importance of Cognitive Biases

For anyone who wants to make rational decisions and understand the world logically, there’s no substitute for a knowledge of cognitive biases. Every single person is prone to fall into at least some cognitive traps just because of the way their brain works. Individual brains learn, over time, to take shortcuts based on what usually works, and if we forget that these are just shortcuts in reasoning, we can overlook the ever-present possibility that they won’t work in the every situation.

The trick is to keep learning about cognitive biases and then observe your own behavior. Starting with the 10 cognitive biases in section 2, think hard about which ones most apply to you. Maybe you’re an independent thinker (so bandwagoning isn’t your issue), but you tend to be overconfident in your views, meaning you may have a tendency to display the Dunning-Krueger effect. The only way to fix your cognitive biases is to learn about them and be honest with yourself about what bad cognitive habits you may have.


V. Cognitive Biases in Popular Culture

Example 1

Shake from Aqua Teen Hunger Force is a clear example of the Dunning-Krueger effect. He’s an idiot who constantly shows his ignorance and comes up with ridiculous ideas – but he’s extremely confident in his own viewpoints. Frylock, on the other hand, is much more intelligent than Shake, but never as brash or assertive.

Example 2

All kinds of advertisements try to get you to buy their product by telling you about how popular it is. This is basically an attempt to exploit the widespread cognitive bias toward bandwagoning – you, as the viewer, are supposed to think “Well, if everyone is buying this car then it must be good!” But that’s faulty reasoning for at least two reasons. For one thing, lots of people can easily make a bad decision, as we saw in §2. For another, each person is different and maybe your needs and preferences aren’t the same as all the others who bought this product.



What is the difference between a cognitive bias and a fallacy?





The Dunning-Krueger effect refers to the fact that ignorant people…





When lots of people are lined up behind one turnstile, leaving another one completely free, this is often due to…





Which of the following is NOT a cognitive bias discussed in this article?






  1. Reply

    good article on cognitive biases

  2. Reply

    This article has helped me a lot …im now more clear on cognitive bias as I desired to. Thanks a lot 🙂

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