List of 125 Most common Bias and Fallacy (And Rare Ones too)

Introduction

Biases and fallacies are two closely related concepts that play a significant role in our decision-making processes, thought patterns, and overall cognition. Understanding them can provide deeper insights into human behavior and can aid in fostering more rational, effective thinking.

Biases are systematic errors in thinking that affect the decisions and judgments that people make. They’re often a result of our brain’s attempt to simplify information processing. Biases are not limited to prejudice or egotism; they can also extend to a wide range of cognitive limitations.

Fallacies, on the other hand, are flaws or errors in reasoning that undermine the logic of an argument. They often occur when an argument is built upon poor logic, misinterpretations, or misrepresentations of evidence. Unlike biases, fallacies aren’t about filtering information or making mental shortcuts but are more concerned with the structure and presentation of an argument.

Here is a generalized difference between bias and fallacy. Anyways both of them impact our rational decision-making process and impact credible decision making. As represented they can impact individuals, groups, institutions, and societies alike.

How are logical fallacies and cognitive biases related

Logical fallacies and cognitive biases are both phenomena that can impede rational thinking and decision-making processes. While they arise from different sources and operate at different levels of reasoning, they share a fundamental connection in terms of their impact on cognition and the potential for distorting judgment.

Logical fallacies, rooted in flawed reasoning, refer to errors in the logical structure of arguments. They are deviations from the principles of valid and sound reasoning, often leading to invalid conclusions. Fallacies can occur due to faulty assumptions, improper deductions, or misleading forms of argumentation. Examples include ad hominem attacks, where personal characteristics are attacked instead of addressing the argument, and the slippery slope fallacy, which assumes that a single event will inevitably lead to a series of increasingly negative outcomes without sufficient evidence.

Cognitive biases, on the other hand, stem from inherent cognitive processes and patterns of thinking. They represent systematic errors in perception, judgment, and decision-making that can arise from heuristics, social influences, or cognitive limitations. Cognitive biases can result in deviations from rationality and objective assessment of information. Examples include confirmation bias, where individuals selectively seek or interpret information that confirms their pre-existing beliefs, and availability bias, which leads to over-reliance on readily available examples or information.

While logical fallacies primarily focus on flaws in reasoning, cognitive biases pertain to cognitive tendencies that influence how information is processed and evaluated. However, there is an overlap between the two, as cognitive biases can contribute to the occurrence and perpetuation of logical fallacies. Biases can affect how individuals construct and perceive arguments, potentially leading to the utilization of fallacious reasoning. Likewise, the presence of fallacies can exploit or exacerbate existing cognitive biases, reinforcing irrational beliefs or faulty decision-making.

List of Bias and Fallacy

In this Comprehensive Blog, we will cover 125 Most Commonly used biases and fallacies, give a layman’s definition and provide a very simple example for the same

A

1.       Actor-Observer Bias: Attributing your own actions to external factors and other’s actions to internal factors.

Example: If you slip and fall, you might blame the wet floor. If someone else slips and falls, you might blame their clumsiness.

2.       Affect Heuristic: Relying on emotions rather than information to make decisions.

Example: Investing in a company you like, even though the financial data shows it’s a bad investment.

3.       Ambiguity Effect: Avoiding options with unknown outcomes.

Example: Choosing a familiar restaurant over a new one because you’re unsure if the new one will be good.

4.       Anchoring Bias: Relying too heavily on the first piece of information.

Example: If the first car’s price you see is $30,000, you might consider it as a reference point and think all cars are expensive.

5.       Attentional Bias: The tendency of our perception to be affected by our recurring thoughts. Example: If you’re thinking about buying a certain type of car, you start noticing it everywhere.

6.       Authority Bias: Giving more credence to the opinions of an authority figure.

Example: Trusting a statement about nutrition simply because it was said by a doctor on TV.

7.       Availability Cascade: A self-reinforcing process in which a collective belief gains more and more plausibility through its increasing repetition in public discourse.

Example: Believing a health scare about a food because it’s frequently mentioned in the media.

8.       Availability Heuristic: Estimating the likelihood of an event based on readily available information.

Example: After hearing news reports about house fires, you might overestimate your own risk of a house fire.

B

9.   Backfire Effect: When presented with evidence against their beliefs, people can reject the evidence and believe even more strongly.

Example: Even after seeing scientific evidence that vaccines are safe, an anti-vaxxer believes even more firmly in their stance.

10.   Bandwagon Effect: Adopting beliefs because others do so.

Example: Starting to like a particular music band just because all your friends like it.

11.   Base Rate Fallacy: Ignoring statistical information in favor of stereotypes or specific examples.

Example: Believing you’ll win the lottery because you heard a story about a lottery winner, ignoring the unfavorable odds.

12.   Belief Bias: Evaluating the strength of an argument based on the believability of its conclusion.

Example: Believing in a medical remedy because you heard it worked for a celebrity, despite lack of scientific evidence.

13.   Ben Franklin Effect: If a person does a favor for someone, they’re likely to do another favor.

Example: If you’ve helped a friend move, you’re more likely to help them on another task.

14.   Blind-spot Bias: Failing to recognize your own cognitive biases.

Example: Thinking you’re less prone to biases than others.

15.   Bystander Effect: The tendency to not offer help in an emergency when others are present.

Example: If a person collapses in a busy area, you might assume someone else will call an ambulance.

C

16.   Cheerleader Effect: People seem more attractive in a group than in isolation.

Example: Thinking that a group of people is full of models, but upon meeting them individually, they seem less attractive.

17.   Choice-Supportive Bias: Remembering chosen options as better than they were.

Example: After a mediocre vacation, remembering only the good parts and convincing yourself it was great.

18.   Clustering Illusion: The tendency to erroneously consider the inevitable “streaks” or “clusters” arising in small samples from random distributions to be non-random.

Example: Seeing patterns in stock market movements and believing that they’re predictable, when they’re really random.

19.   Confirmation Bias: Preferring information that confirms preexisting beliefs.

Example: If you believe that left-handed people are more creative, you’re more likely to notice when a left-handed person is creative and dismiss instances of right-handed creativity.

20.   Conjunction Fallacy: Believing that more specific conditions are more probable than general ones.

Example: Thinking it’s more likely for a person to be a vegan yoga teacher, rather than just a vegan.

21.   Conservatism Bias: Favoring older information over new evidence.

Example: Believing eating fat makes you fat, even after new studies show certain fats are healthy.

22.   Consistency Bias: Incorrectly remembering one’s past attitudes and behaviour as resembling present attitudes and behavior.

Example: You might think that you’ve always loved a specific dish, even though you disliked it as a child.

23.   Contrast Effect: Evaluating stimuli based on contrast with previous stimuli.

Example: After lifting a heavy box, a lighter one seems even lighter than it is.

24.   Current Moment Bias: The tendency to overvalue immediate rewards.

Example: Choosing to spend money on a vacation now rather than saving for retirement.

25.   Curse of Knowledge: Difficulty in understanding someone else’s ignorance when you are an expert in a field.

Example: A math professor being unable to understand why a student can’t solve an “easy” problem.

D

26.   Decoy Effect: Changing your preference between two options when presented with a third, inferior option.

Example: If you’re deciding between a small and a medium coffee, and a slightly larger but much more expensive large size is introduced, you may now see the medium size as a better value and choose it.

27.   Defensive Attribution Hypothesis: Attributing more blame to a harm-doer as the outcome becomes more severe or as personal or situational similarity to the victim increases.

Example: Blaming a reckless driver more when they cause a severe accident than when they just cause a minor fender bender.

28.   Denomination Effect: Spending more when money is in smaller denominations.

Example: You’re more likely to spend five $1 bills than a $5 note.

29.   Dunning-Kruger Effect: Unskilled individuals overestimating their competence.

Example: Someone who’s bad at singing believing they’re good because they can’t perceive their lack of skill.

30.   Duration Neglect: The neglect of the duration of an episode in determining its value.

Example: Remembering only the ending of a painful experience and not how long the pain lasted.

E

31.   Effort Justification: When people put effort into a task, they justify the effort by elevating their opinion of the task.

Example: After a grueling initiation, a club member values their membership more because it was hard to get.

32.   Endowment Effect: Valuing something more because you own it.

Example: Setting a higher selling price for your used car than what you would be willing to pay for it.

33.   Experimenter’s Bias: An experimenter’s expectations influence the outcome of an experiment. Example: If a researcher believes a medication will have a certain effect, they might unknowingly influence the results to align with their expectation.

34.   Extension Neglect: Ignoring the size of the set when evaluating the likelihood of a particular event.

Example: Judging that a single hospital room is likely to be unoccupied, even in a large hospital with hundreds of rooms.

35.   Extrinsic Incentives Bias: An overemphasis on extrinsic rewards when interpreting why others behave the way they do.

Example: Assuming an artist paints only to sell their paintings, and not considering that they might enjoy painting.

F

36.   False Consensus Effect: Believing more people share your opinion than they actually do. Example: Assuming all your friends will vote for the same candidate as you.

37.   False Memory: A mental experience that is mistakenly taken to be a veridical representation of an event from one’s personal past.

Example: You might remember the fish you caught on a trip as bigger than it actually was.

38.   Focusing Effect: Placing too much importance on one aspect of an event.

Example: Overestimating the influence of the weather on your happiness after moving to a better climate.

39.   Forer Effect (Barnum Effect): Individuals give high accuracy ratings to descriptions of their personality that supposedly are tailored specifically for them, but are vague and general enough to apply to a wide range of people.

Example: Believing your horoscope is specifically about you, when it could apply to anyone.

40.   Framing Effect: Drawing different conclusions based on how information is presented.

Example: You may be more likely to eat chicken if it’s labeled “90% fat-free” instead of “contains 10% fat”.

41.   Fundamental Attribution Error: Overemphasizing personality traits and underemphasizing situational factors when judging others’ behavior.

Example: If a person is yelling, you might think they’re naturally aggressive, not that they’re under stress.

42.   Galatea Effect: Where people succeed or underperform because they think they should. Example: If you think you should be good at math because you’re Asian, you might perform better at math.

G

43.   Gambler’s Fallacy: Believing that past events affect the probability of something happening in the future.

Example: After flipping a coin and getting tails five times, you might think heads is due.

44.   Gambler’s Fallacy: Believing that past events affect future probabilities in independent trials.

Example: After a string of coin tosses landing on heads, believing that tails is “due” to come up next.

45.   Google Effect: The tendency to forget information that can be found readily online.

Example: Forgetting a fact because you know it can be easily googled.

46.   Groupthink: The practice of making decisions as a group in a way that discourages individual responsibility.

Example: A team might decide to implement a flawed plan because no one wants to contradict the leader.

H

47.   Halo Effect: Letting one positive aspect of a person overshadow other traits.

 Example: Thinking a good-looking person must be intelligent and kind.

48.   Hindsight Bias: Believing past events were predictable.

Example: After a sports team loses, you might say, “I knew they were going to lose.”

49.   Horn Effect: Allowing one negative trait to overshadow other traits.

Example: Assuming a person who is always late is also unproductive and irresponsible.

50.   Hostile Attribution Bias: The tendency to interpret others’ behaviors as having hostile intent, even when the behavior is ambiguous or benign.

Example: You see a friend in town and they don’t greet you, you assume they’re mad at you, but they may just not have seen you.

51.   Hot-Hand Fallacy: Believing a person who has been successful has a higher chance of further success.

Example: Believing a basketball player who has made several shots will make the next one too.

52.   Hyperbolic Discounting: Preferring smaller, immediate rewards over larger, delayed ones. Example: Choosing $50 today over $100 a year from now.

I

53.   Identifiable Victim Effect: The tendency to respond more strongly to a single identified victim than to a large group of victims.

Example: Donating to help a single child in need, but not to a fund that helps thousands of children.

54.   IKEA Effect: Valuing things you have assembled or created yourself more than they are objectively worth.

Example: Placing high value on the furniture you put together, even if it’s a bit wobbly.

55.   Illusion of Control: Believing you can control or influence outcomes that you can’t.

Example: Thinking you can control traffic on your way home.

56.   Illusion of Transparency: Overestimating others’ ability to know our mental state.

Example: Thinking your nervousness is obvious to others during a presentation when it’s not really noticeable.

57.   Illusory Correlation: Perceiving a relationship between two unrelated events.

Example: Believing black cats bring bad luck because you had a bad day once when a black cat crossed your path.

58.   Illusory Superiority: Overestimating our own qualities and abilities, compared to others. Example: Thinking you’re a safer driver than the average driver.

59.   Information Bias: Believing more information is better, even if it’s irrelevant.

Example: Asking for more specifications about a laptop, when all you use it for is browsing and document editing.

60.   Ingroup Bias: Preferring members of your own group over others.

Example: Favoring the opinion of your fellow countrymen over foreigners during a discussion.

61.   Irrational Escalation: The phenomenon where people justify increased investment in a decision, based on the cumulative prior investment, despite new evidence suggesting that the decision was probably wrong.

Example: Spending more money on an old car repair, even when the repair cost exceeds the car’s worth.

J

62.   Just-Noticeable Difference Effect (Weber–Fechner Law): The idea that the change in a stimulus that will be just noticeable is a constant ratio of the original stimulus.

Example: Adding 1 pound to a 10-pound weight will be more noticeable than adding 1 pound to a 100-pound weight.

63.   Just-world Hypothesis: Believing that good things happen to good people, and bad things happen to bad people.

Example: Blaming victims for their misfortune, such as assuming someone who lost their job must have been lazy.

L

64.   Law of the Instrument: Over-reliance on a familiar tool or methods, ignoring or under-valuing alternative approaches. “If all you have is a hammer, everything looks like a nail.”

Example: Always using medication to relieve headaches, when stress relief techniques could help too.

65.   Loss Aversion: People’s tendency to prefer avoiding losses to acquiring equivalent gains. Example: It’s better to not lose $5 than to find $5.

M

66.   Mere Exposure Effect: Preferring things because you’re familiar with them.

Example: Preferring the version of a song you heard first, over a cover version.

67.   Misinformation Effect: Remembering past information inaccurately due to later exposure to misleading information.

Example: A witness of a crime might wrongly recall the events after being exposed to faulty news reports about the crime.

68.   Money Illusion: Focusing on nominal rather than real value (i.e., inflation-adjusted).

Example: Being happy with a 2% pay raise, when inflation is 3%.

N

69.   Naive Realism: Believing that we see reality as it really is – objectively and without bias. Example: Assuming that facts that you perceive are the absolute truth and dismissing others’ perspectives.

70.   Name-Letter Effect: The tendency to prefer the letters in one’s own name over other letters in the alphabet.

Example: You may be more likely to live in a place that starts with the same letter as your name (i.e., Sam living in Seattle).

71.   Negativity Bias: Paying more attention to negative details than positive ones.

Example: Remembering the one rude comment someone made and forgetting all their compliments.

72.   Neglect of Probability: The disregard of probability when making a decision under uncertainty. Example: Playing the lottery despite the low chance of winning.

73.   Normalcy Bias: The refusal to plan for or react to a disaster that has never happened before. Example: People not evacuating for a severe storm because they’ve never experienced one before.

74.   Not Invented Here: Aversion to contact with or use of products, research, standards, or knowledge developed outside a group.

Example: A company refusing to adopt a more efficient technology because it was developed by a competitor.

O

75.   Observer-expectancy Effect: Observers influence the behavior of those they observe.

Example: Students perform better on a test when their teacher expects them to do well.

76.   Omission Bias: The tendency to judge harmful actions as worse than equally harmful inactions. Example: Thinking it’s worse to accidentally harm someone by action, rather than failing to save them due to inaction.

77.   Optimism Bias: Believing that the future will be better and that negative events are less likely to happen to us.

Example: Thinking that you’re less likely than others to get a chronic disease.

78.   Ostrich Effect: Ignoring an obvious problem.

Example: Avoid looking at your credit card bill because you know you spent too much.

79.   Outcome Bias: Judging a decision based on its outcome rather than how the decision was made. Example: Thinking an investment decision was good just because it ended up paying off.

80.   Outgroup Homogeneity Bias: Perceiving members of outside groups as more alike, while members of your own group are seen as more diverse.

Example: Assuming all members of a foreign sports team have the same skills and tactics.

81.   Overconfidence Effect: Believing you’re more correct than you actually are.

Example: Being sure your answers on a test are correct when they’re not.

82.   Overgeneralization: Applying the conclusions from one experience to other experiences that may not actually apply.

Example: Believing that all fast-food restaurants have poor service because of one bad experience.

P

83.   Paradox of Choice: Too many choices can lead to anxiety and regret over whether you made the right decision.

 Example: Feeling overwhelmed by choosing a college major because there are so many options.

84.   Pareidolia: Seeing recognizable objects or patterns in unrelated objects.

Example: Seeing faces in the patterns of a carpet.

85.   Parkinson’s Law of Triviality: Members of an organization give disproportionate weight to trivial issues.

Example: A team spends more time discussing the color of a product than more important functional aspects.

86.   Peak-End Rule: Remembering only the peak and end of an event.

Example: Judging a vacation as good if you had a great highlight and a good end, even if the rest was mediocre.

87.   Pessimism Bias: Overestimating the likelihood of negative outcomes.

 Example: Believing you’re going to fail an exam, even though you’ve studied thoroughly and got good grades on past exams.

88.   Placebo Effect: Experiencing perceived improvement due to belief in treatment, not the treatment itself.

Example: Feeling relief from a headache after taking a sugar pill you believe is a powerful painkiller.

89.   Planning Fallacy: The tendency to underestimate task-completion times.

Example: Thinking it will only take an hour to build IKEA furniture, when it actually takes three.

90.   Post-Purchase Rationalization: Convincing yourself a purchase was worth it after the fact. Example: After buying an expensive gadget, you might emphasize its positive features and downplay the high cost.

91.   Primacy Effect: The tendency to remember the first information we perceive.

Example: In a list, we are more likely to remember the first items.

92.   Procrastination: The act of delaying or postponing a task or set of tasks.

Example: Choosing to watch TV now and study for a test later, despite knowing you should study now.

93.   Pro-Innovation Bias: Overvaluing the usefulness of an innovation.

Example: Believing every business should be on social media, even when it’s not appropriate for some.

94.   Projection Bias: Assuming others share the same beliefs and attitudes as us.

Example: Assuming your friend must also dislike a certain movie because you do.

R

95.   Reactance: The urge to do the opposite of what someone wants you to do out of a need to resist a perceived attempt to constrain your range of choices.

Example: A teenager uses more slang when their parent asks them not to.

96.   Recency Bias: Overemphasizing the most recent information.

Example: Changing your opinion on a topic after reading a single, recent article, even though it contradicts what you’ve read in the past.

97.   Recency Illusion: The illusion that a word or language usage you have noticed only recently is an innovation when it is in fact long-established.

Example: Believing the usage of “literally” to mean “figuratively” is a recent change.

98.   Regression to the Mean: Misunderstanding that extreme performance is likely to be followed by more average performance.

Example: After an extraordinary sales quarter, expecting the high performance to continue, when it’s more likely to return to average levels.

99.   Regret Aversion: Anticipating regret and, therefore, avoiding taking action that could lead to this feeling.

Example: Not taking a job offer in a new city because you’re afraid you’ll regret moving away from your family.

100. Representativeness Heuristic: Making judgments about likelihood based on resemblance to stereotypical cases.

Example: Believing that a shy person must work as a librarian, because your stereotype of librarians is that they are shy and quiet.

101.  Restraint Bias: Overestimating your self-control.

Example: Buying a big bag of candy, thinking you’ll make it last, then eating it all in one sitting.

102.  Rhyme-as-Reason Effect: Rhyming statements are perceived as more truthful.

Example: Believing “An apple a day keeps the doctor away” just because it rhymes.

S

103.  Scarcity Bias: Valuing something more if it’s scarce.

 Example: Buying a product you don’t really need just because it’s on a limited-time offer.

104.  Selective Perception: Allowing expectations to affect perception.

Example: Soccer fans see fouls committed by the other team but not by their own.

105.   Self-Serving Bias: Attributing success to personal factors and failures to external factors. Example: If you win a game of tennis, you might attribute it to skill. If you lose, you might blame the windy weather.

106. Semmelweis Reflex: The tendency to reject new evidence that contradicts an established paradigm.

Example: Dismissing new research findings because they contradict traditional beliefs.

107.   Serial Position Effect: Remembering the first and last items in a series better than those in the middle.

Example: On a grocery list, remember the first and last items more easily.

108.  Social Comparison Bias: Judging your own abilities based on others.

Example: Feeling like you’re not good at drawing because you compare your work to professional artists.

109.  Social Loafing: People are prone to exert less effort on a task if they are in a group versus when they work alone.

Example: In a group project, some members might do less work because they think others will pick up the slack.

110.  Spatial Agency Bias: The tendency for people to view self-generated actions as being less time-consuming compared to those performed by others.

Example: Thinking it takes you less time to complete a household chore than it takes your roommate.

111. Spotlight Effect: Overestimating the amount other people notice your appearance or behavior.

Example: Feeling self-conscious about a small stain on your shirt, when nobody else has probably noticed.

112.  Status Quo Bias: Preferring things to stay the same.

Example: Sticking to the same routine because it’s comfortable, even if a change could be beneficial.

113. Stereotyping: Expecting a group or person to have certain qualities without having real information about the person.

Example: Believing programmers are introverted, without knowing any programmers personally.

114.  Sunk Cost Fallacy: Continuing a behavior due to previously invested resources.

Example: Continuing to eat a meal at a restaurant even after you’re full, because you’ve paid for it and don’t want it to go to waste.

115.  Survivorship Bias: Overlooking failures and focusing on successes.

Example: Believing becoming an entrepreneur is easy because you hear more about successful entrepreneurs than failed ones.

116.  System Justification: The tendency to defend and bolster the status quo.

Example: Opposing political change because you believe the current system is the best possible one.

T

117.  Trait Ascription Bias: The tendency for people to view themselves as relatively variable in terms of personality, behavior, and mood while viewing others as much more predictable. Example: Believing that your mood and behaviors change a lot, but your friends stay the same.

118. Triviality: The tendency to give disproportionate weight to trivial issues.

Example: Focusing more on spelling mistakes in an essay rather than the content.

U

119.  Under confidence Effect: Underestimation of one’s abilities or the accuracy of one’s beliefs.

 Example: Believing you will fail a test, despite studying and being well-prepared.

120. Unit Bias: Believing there is an optimal size for portions or tasks.

121.  Example: Eating a whole burger even when you’re full, because you view it as a single unit that should be finished.

V

122. Von Restorff Effect: A cognitive bias that occurs when an unusual item in a list is more likely to be remembered than common items.

Example: Remembering the one red apple in a list of green apples.

W

123.  Wishful Thinking: The formation of beliefs and making decisions according to what might be pleasing to imagine instead of by appealing to evidence, rationality, or reality.

Example: Thinking you’ll win the lottery and quit your job, even though the chances are extremely slim.

Z

124. Zero-risk Bias: Preferring to eliminate a small risk entirely rather than reducing a larger risk.

Example: Paying for a guarantee on an item that already has a very low failure rate.

125. Zweig’s Paradox: The less the public knows about a market or business, the more they expect in it.

 Example: People investing in a startup company with no understanding of its business model or market, simply because they expect high returns.

FAQ

Samrat Saha

Samrat is a Delhi-based MBA from the Indian Institute of Management. He is a Strategy, AI, and Marketing Enthusiast and passionately writes about core and emerging topics in Management studies. Reach out to his LinkedIn for a discussion or follow his Quora Page