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Confirmation Bias: Definition, Examples and Effects

Updated: May 26

Definition: Confirmation bias is a cognitive bias that causes people to search for, interpret, and remember information in a way that confirms their preexisting beliefs. It is a type of thinking that can lead to poor decision-making and a lack of objectivity.

People display this bias when they gather or remember information selectively, or when they interpret it in a biased way. The effect is stronger for emotionally charged issues and for deeply entrenched beliefs.


1. Remi thinks to himself "I think I usually wake up with a song in my head" and, over the next week or so, whenever he wakes up with a song in his head, he notices it and thinks "Yes, see! This confirms my belief!" However, he doesn't pay attention to the times that he doesn't wake up with a song in his head. If he did, he'd notice that they slightly outnumber the times that he does. It's easy to fall into traps like this because something not happening is often unremarkable and slips by our notice.

2. Susan is a teacher who suspects that her students might have used Chat-GPT to write their homework, despite that being against the rules. She puts the text of each student's homework into Chat-GPT and asks the AI whether it is the author. Chat-GPT claims to have authored every piece of homework, so Susan gives every student a failing grade. The problem is that Susan only looked for evidence that confirmed her belief. If she had given Chat-GPT several texts she knew wasn't authored by Chat-GPT and asked it whether it was the author, she might have discovered that Chat-GPT sometimes claims to have authored things it hasn't. This would have been reason to doubt her belief and not give failing grades to all her students!

Effects: Confirmation bias can lead to poor decision-making and a lack of objectivity. It can also lead to a distorted view of reality, as people may only pay attention to information that confirms their beliefs and ignore information that contradicts them. This can lead to a lack of critical thinking and an inability to consider alternative perspectives. Additionally, confirmation bias can lead to a lack of creativity, as people may be less likely to explore new ideas or consider alternative solutions.

Do you want to expand your knowledge on this topic? Read our full in-depth article on cognitive biases.

Do you have extra 15 minutes today? Take our fun and interactive quiz to learn which of 16 reasoning styles you use, your overall level of rationality, and what you can do now to improve your rationality skills.

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