50 Cognitive Biases
To Know So You Can Reason Effectively
Categories
So
Be
🪞
Fundamental Attribution Error
We judge others on their personality or fundamental character, but we judge ourselves on the situation.
“Sally is late to class; she's lazy. You're late to class; it was a bad morning.”
So
Be
Mo
🤳
Self-Serving Bias
Our failures are situational but our successes are our responsibility.
“You won that award due to hard work rather than help or luck. Meanwhile, you failed a test because you hadn't gotten enough sleep.”
So
Be
Po
❤️
In-Group Favoritism
We favor people who are in our in-group as opposed to an out-group.
“Francis is in your church, so you like Francis more than Sally.”
So
Be
Po
🚙
Bandwagon Effect
Ideas, fads, and beliefs grow as more people adopt them.
“Sally believes fidget spinners help her children. Francis does too.”
So
Be
Po
😵💫
Groupthink
Due to a desire for conformity and harmony in the group, we make irrational decisions often to minimize conflict.
“Sally wants to go get ice cream. Fancis wants to shop for t-shirts. You suggest getting t-shirts with pictures of ice cream on them.”
So
Be
Po
😇
Halo Effect
If you see a person as having a positive trait, that positive impression will spill over into their other traits. (This also works for negative traits.)
“Taylor could never be mean; she's so cute!”
Me
So
Be
Po
🏆
Moral Luck
Better moral standing happens due to a positive outcome; worse moral standing happens due to a negative outcome.
“X culture won X war because they were morally superior to the losers.”
So
Be
Po
👨👩👧👦
False Consensus
We believe more people agree with us than is actually the case.
“Everybody thinks that!”
Me
So
Be
Po
📘
Curse of Knowledge
Once we know something, we assume everyone else knows it, too.
“Alice is a teacher and struggles to understand the perspective of her new students.”
Me
So
🔦
Spotlight Effect
We overestimate how much people are paying attention to our behavior and appearance.
“Sally is worried everyone is going to notice how lame her ice cream t-shirt is.”
Me
Le
Be
Mo
Po
💭
Availability Heuristic
We rely on immediate examples that come to mind while making judgments.
“When trying to decide on which store to visit, you choose the one you most recently saw an ad for.”
Me
So
Po
🛡
Defensive Attribution
As a witness who secretly fears being vulnerable to a serious mishap, we will blame the victim less and attacker more if we relate to the victim.
“Sally sat at a green light playing with her phone and got rear-ended. Greg, who texts and drives, got out and yelled at the person who smacked into her.”
Me
So
Be
Po
🌎
Just-World Hypothesis
We tend to believe the world is just; therefore, we assume acts of injustice are deserved.
“Sally's purse was stolen because she was mean to Francis about their T-shirt and had bad karma.”
Me
So
Be
Po
📷
Naïve Realism
We believe that we observe objective reality and that other people are irrational, uninformed, or biased.
“I see the world as it really is — other people are dumb.”
Me
So
Be
Po
🎁✋
Naïve Cynicism
We believe that we observe objective reality and that other people have a higher egocentric bias than they actually do in their intentions/actions.
“The only reason this person is doing something nice is to get something out of me.”
Me
Be
♍️
Forer Effect (aka Barnum Effect)
We easily attribute our personalities to vague statements, even if they can apply to a wide range of people.
“This horoscope is so accurate!”
Me
So
Le
Be
Mo
Po
😤
Dunning-Kruger Effect
The less you know, the more confident you are. The more you know, the less confident you are.
“Francis confidently assures the group that there's no kelp in ice cream. They do not work in the dairy industry.”
Me
Le
Be
Mo
⚓️
Anchoring
We rely heavily on the first piece of information introduced when making decisions.
“That's 50% off? It must be a great deal.”
Me
Le
Be
📱
Automation Bias
We rely on automated systems, sometimes trusting too much in the automated correction of actually correct decisions.
“Your phone auto-corrects "its" to "it's", so you assume it is right.”
Me
Le
Be
🔎
Google Effect (aka Digital Amnesia)
We tend to forget information that's easily looked up in search engines.
“What was the name of that actor in that funny movie? I've looked it up about eight times…”
So
Mo
Po
🥊
Reactance
We do the opposite of what we're told, especially when we perceive threats to personal freedoms.
“One of Alice's students refuses to do his homework even though both she and his parents tell him to.”
Me
Le
Be
Po
🛸
Confirmation Bias
We tend to find and remember information that confirms our perceptions.
“You can confirm a conspiracy theory based on scant evidence while ignoring contrary evidence.”
Me
Le
Be
Po
🗺
Backfire Effect
Disproving evidence sometimes has the unwarranted effect of confirming our beliefs.
“The evidence that disproves your conspiracy theory was probably faked by the government.”
Me
So
Le
Be
Po
📺
Third-Person Effect
We believe that others are more affected by mass-media consumption than we ourselves are.
“You've clearly been brainwashed by the media.”
Me
Le
Be
Po
💭
Belief Bias
We judge an argument's strength not by how strongly it supports the conclusion but how plausible the conclusion is in our own minds.
“Sally mentions facts supporting your conspiracy theory, which you accept wholeheartedly despite her having little evidence.”
Me
So
Le
Be
Mo
Po
🕴🕴🕴
Availability Cascade
Tied to our need for social acceptance, collective beliefs gain more plausibility through public repetition.
“A story about razor blades appearing in candy eventually led to many people no longer offering homemade treats on Halloween in America.”
Me
So
Be
Po
🗡
Declinism
We tend to romanticize the past and view the future negatively, believing that societies/institutions are by and large in decline.
“In my day, kids had more respect!”
Me
So
Le
Be
Mo
Po
🛑
Status Quo Bias
We tend to prefer things to stay the same; changes from the baseline are considered to be a loss.
“Even though an app's terms of service invade Sally's privacy, she's rather not switch to another app.”
Me
Be
Mo
🗑
Sunk Cost Fallacy (aka Escalation of Commitment)
We invest more in things that have cost us something rather than altering our investments even if we face negative outcomes.
“In for a penny, in for a pound!”
Me
Be
Mo
🎲
Gambler's Fallacy
We think future possibilities are affected by past events.
“Alice has lost nine coin tosses in a row so she's sure to win the next one!”
Be
Mo
Po
0️⃣
Zero Risk Bias
We prefer to reduce small risks to zero, even if we can reduce more risk overall with another option.
“You should probably buy the warranty.”
So
Le
Be
Mo
Po
🖼
Framing Effect
We often draw different conclusions from the same information depending on how it's presented.
“Alice hears her favorite candidate is "killing it" with 45% approval. Sally hears the candidate is "disappointing" with a 45% rating. They have wildly different interpretations of the statistic.”
Me
So
Le
Be
Po
😔
Stereotyping
We adopt generalized beliefs that members of a group will have certain characteristics despite not having information about the individual.
“That guy with the fancy mustache is a hipster. He probably has a vinyl collection.”
Me
So
Le
Be
Mo
Po
👥👥
Outgroup Homogeneity Bias
We perceive out-group members as homogeneous and our own in-groups as more diverse.
“Alice is not a gamer but she believes all gamers are the same.”
So
Be
Mo
Po
👩💼
Authority Bias
We trust and are more often influenced by the opinions of authority figures.
“My teacher told me this was fine.”
Me
Be
Mo
👨⚕️
Placebo Effect
If we believe a treatment will work, it often will have a small physiological effect.
“Alice was given a placebo for her pain and her pain decreased.”
So
Be
Mo
Po
🧗
Survivorship Bias
We tend to focus on those things that survived a process and overlook the ones that failed.
“Greg tells Alice her purse business is going to be great because a successful fashion company had the same strategy. (But 10 other failed companies also had the same strategy.)”
Me
Le
Be
😵
Tachypsychia
Our perceptions of time shift depending on trauma, drug use, and physical exertion.
“When the car almost hit me, time slowed down…”
Me
So
Mo
Po
🚲
Law of Triviality (aka "Bike-Shedding")
We give disproportionate weight to the trivial issues, often while avoiding more complex issues.
“Rather than figuring out how to help the homeless, a local city government spends a lot of time discussing putting in a bike path and bike sheds.”
Me
Be
✅
Zeigarnik Effect
We remember incomplete tasks more than completed ones.
“Greg feels guilty for never getting anything done, until he sees all of the tasks he's checked off on his task list.”
So
Be
Mo
🪑
IKEA Effect
We place higher value on things we partially created ourselves.
“Don't you love this pot I spent $20 on? I painted it myself!”
So
Be
Mo
Po
💵
Ben Franklin Effect
We like doing favors; we are more likely to do another favor for someone if we've already done a favor for them than if we had received a favor from that person.
“Greg loaned Francis a pen. When Francis asked to borrow $5, Greg did it readily.”
Be
Mo
🚑
Bystander Effect
The more other people are around, the less likely we are to help a victim.
“In a crowd of students, no one called 911 when someone got hurt in a fight.”
Me
So
Le
Be
🎤
Suggestibility
We, especially children, sometimes mistake ideas suggested by a questioner for memories.
“So did you fall off the couch before or after your mom hit you?”
Me
So
Be
🤔
False Memory
We mistake imagination for real memories.
“Greg is certain Sally told a really funny joke about pineapples, but that joke actually came from a TV show.”
Me
So
Be
💡
Cryptomnesia
We mistake real memories for imagination
“Greg thinks he visited a graveyard, but he's pretty sure he just had a spooky dream.”
Me
Be
📈
Clustering Illusion
We find patterns and "clusters" in random data.
“That cloud looks like your cat!”
Me
Be
😞
Pessimism Bias
We sometimes overestimate the likelihood of bad outcomes.
“Nothing will ever get better.”
Me
Be
😁
Optimism Bias
We sometimes are over-optimistic about good outcomes.
“It's going to turn out great!”
Me
So
Le
Be
🧑🦯
Blind Spot Bias
We don't think we have bias and we see it on others more than ourselves.
“I am not biased!”