Did you know your brain is secretly lazy? To save energy, our minds rely on mental shortcuts called heuristics, which often cause errors in logic. In this post, we’ll expose eight common cognitive biases—like Confirmation Bias, the Dunning-Kruger Effect, and the Barnum Effect—that quietly distort your thinking and cloud your judgment. Discover how these psychological blind spots trick your memory, choices, and perception.
Let’s first make sure we have a good idea of what a cognitive bias is in general. We all have cognitive biases, as these are shortcuts that our brain takes to help lighten its load, but that have a good likelihood of resulting in errors in thinking. These are very similar—if not the same thing—as a heuristic, which is another term you are likely to encounter.
One thing to keep in mind is that we’ll mostly be discussing cognitive biases that relate to our thoughts, but there will be some here that might focus less on thoughts and instead more often influence our perception in other ways, such as being more visual or relating more to our memory. This is something some may not realize, a cognitive bias does not have to be from our thoughts; they can also affect other information that we process.
Cognitive biases are likely to lead to thinking about something in a manner that might be overly simplistic and uncritical. At the same time, we don’t want to have to think through every thought in a critical manner as this would be extremely taxing on our brain. Therefore, these mental shortcuts give our brain a needed break. We want to be mindful of these though, as our brain will take shortcuts any chance it gets. Therefore, we have to be careful to engage in critical thinking when needed and check ourselves for these cognitive biases.
Confirmation Bias
Let’s begin with possibly the most well-known of the cognitive biases, confirmation bias. This is a tendency where people are more likely to believe, select, focus on or remember information that fits their existing beliefs. They are also more likely to discount or disregard information that does not fit with their existing beliefs. This is not necessarily limited to one’s beliefs though, it can also include the values they hold as important, previous decisions that they have made, as well as any preconceptions, specific views or expectations they have.
Here’s an example to illustrate confirmation bias. Beth loves coffee and believes it has no negative effects. She decides to search the internet for recent articles about coffee. She finds articles that are positive and negative related to the effects of coffee one one’s health, but she only reads those that seem more positive. A couple of days later, she talks to a friend about the articles and says there were so many positive things written about coffee but does not mention that she also saw negative articles that she didn’t read.
Gambler’s Fallacy
Second, let’s look at the Gambler’s Fallacy, also known as the Monte Cristo Fallacy. The American Psychological Association defines this as “a failure to recognize the independence of chance events, leading to the mistaken belief that one can predict the outcome of a chance event on the basis of the outcomes of past chance events”. In other words, when there is a small chance something can happen, and the chance of that is only based on chance, they can believe their chances increase with each chance, even though their actual odds remain the same throughout.
Let’s look at an example to see the Gambler’s fallacy in action. Jeff is at the casino and has put quite a bit of money in a slot machine. He has not one yet, not even a small amount. As he puts more money in, he is getting more excited and comments on how he hasn’t one yet and that this must mean the big one is coming. In reality, the odds of winning are the same on each pull of a slot machine. Even though he hasn’t been winning, this does not change his odds.
Here’s another way to say this: With something like gambling, for each gamble, the odds are the same. The more we play, this doesn’t change the odds. Let’s imagine we have a 1 in 1000 chance of winning. Those are the odds each time we play. We have played 999 times and have not won yet. The Gambler’s Fallacy would say that we are going to assume then that the 1,000th time we play we will win. In reality, that is not guaranteed. We have the same odds of winning on our first play, our 20th, our 999th, and our 1,000th.
Pareidolia
The third cognitive bias is called Pareidolia. This is a tendency where people can see a pattern in something that is meaningless. Pareidolia most often occurs visually, such as seeing a face in the clouds. Pareidolia is a type of Apophenia, which is a more general pattern of finding connection in things that are unrelated and do not actually have a connection.
I’ll give a personal example of pareidolia. I was on a trip to Ireland and on a bus tour. During the tour, the guide shared a story of a giant that created the Giant’s Causeway. This story ended at a location where there was a formation that looked like a head, which the guide said was the giant. This was a fun story and added to the experience of the tour, showing how these biases are not all bad, but the reality is that it was just a rock formation.
Recency Bias
Fourth, the recency bias. This is in a broad category of memory biases. With recency bias, events that have occurred more recently are given more favor or preference over events that have occurred historically. In other words, the most recent event is the one that is favored.
Here’s an example. Jill is completing performance reviews for the members of her team. Milly has been an awesome employee over he last three years on Jill’s team. However, Milly gave a team presentation last week and struggled throughout the presentation with multiple typos in the presentation, she stumbled over many words, and struggled to give clear answers to questions from those watching the presentation. It turns out Milly had a death in the family she had learned of earlier in the day. When Jill completes Milly’s evaluation, she keeps rating Milly’s performance lower. This shows how Jill had lost sight of Milly’s performance overall and is being highly influenced by the recent presentation.
Peak-End Rule
Fifth is the Peak-End Rule. Before we talk about this one, we need to define a couple of things. When someone is engaged in an activity, the most positive or negative parts of the activity are the peaks. The last part of the activity is the end, of course. With that, the peak end rule states that people don’t usually consider the event or activity as a whole, but instead place the most emphasis on the peak and the end of the event or activity.
For example, Mia spent the day at a theme park, and it was a rough day. The heat was intense, many of the food stands were closed, she dropped her ice cream, the other people at the park were crabby because of the heat, and the day was filled with negatives. However, Mia did get to go on her favorite ride multiple times, getting her favorite spot on the coaster each ride. As she was leaving the park, she happened upon a drawing where she won a free season pass to the park. Looking back on the day, she remembers it very positively, telling people about how lucky she was to get her favorite spot over and over, and how her luck continued with winning the season pass. This illustrates how memories of her peak experience—her favorite ride—and the end experience—winning the season pass—dominate her memory and override the many other negative experiences that day.
Dunning-Kruger Effect
Sixth, the Dunning-Kruger effect is a popular cognitive bias that you may have heard of. This cognitive bias is that people who have a relatively low skill level in something tend to overestimate their ability in that area. This is often the result of the person not recognizing that their level of knowledge or skill on the topic is on the lower end.
Let’s look at this example of the Dunning-Kruger Effect. Steve is finishing up his first abnormal psychology course in college. Discussing what he has learned over the semester, he tells his friends about different mental health disorders. He says he’s not sure why people have to go to school so long to be a psychologist as this one class seemed to teach everything someone would need to know. He comments on how he is pretty sure he could make accurate diagnoses already. This shows the Dunning-Kruger effect. Steve has completed one abnormal psychology course, and is likely to have some knowledge of mental health diagnoses. However, he is likely missing many of the other factors that can relate to diagnosing, such as culture, differential diagnoses, assessment, and so forth.
Barnum Effect
The seventh of the cognitive biases that we’re discussing is the Barnum effect. This cognitive bias occurs when people are given a description of their personality that is actually vague, but the person perceives and rates this description as highly accurate. These types of descriptions are common in astrology and fortune telling. This effect gets its name from well-known showman P. T. Barnum
Let’s imagine that you take an online personality test and these are the results you get: You possess a strong desire for other people to like you, and find that you are often critical of yourself. While you have a few weaknesses, you also have many positive traits that aren’t fully seen and appreciated.
Does this seem to accurately describe you? Likely, you feel like the results do describe you or are accurate for you. This is an example of how you can write vague statements and that these can then be presented in a way that feels very accurate and personal.
Illusory Truth Effect
Finally, we are on to the last cognitive bias. This is the illusory truth effect, which goes by many other names. You may hear it called the illusion of truth effect, validity effect, truth effect, or the reiteration effect. No matter what name it goes by, the bias is the same. The illusory truth effect is that people can start to believe false or incorrect information when they are repeatedly given this information. People can have a tendency to rate information as correct when they are more familiar with that information, which may be a factor in how this bias occurs.
Bill sees a social media post that says that half a gallon of grape juice will cure joint pain in just a couple of days. He notices the post is not from a reputable source and is certain this is made up. He decides to look it up out of curiosity. Sure enough, he finds again and again that this claim is incorrect. He keeps seeing posts about this claim though, and each time shakes his head knowing they are false claims. A couple of months go by and Bill has not seen these posts recently. However, he starts getting knee pain after starting to work out more. He doesn’t find the pain to be relieved with his usual methods and remembers that he had seen posts about half a gallon of grape juice curing joint pain. He decides to try this out. Bill has succumbed to the illusory truth effect. Despite looking up this claim, finding source after source saying it was false, the repeated interactions with the false information outweighed the facts he had found.
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