78 Types of Bias

A bias is a distortion of judgment that relies on a factor other than logic in coming to conclusions.

Biases may occur either due to fallacies (i.e. logical errors in thinking) or heuristics (where you take a shortcut in your mind to get to the conclusion without thinking things through).

Biases can lead to sub-optimal thinking and decision-making. However, they can also be useful, such as when our bias is based on a logical assumption. We use biases, for example, when relying on the views of experts over laypeople on a topic.

Nevertheless, it’s good to be aware of how biases work, and all the different types, in order to know when people (including yourself) are using biases, and to understand their effects.

Types of Bias

Ageism Bias
Ageism bias involves holding prejudices against people based on their age. For example, you might believe that younger employees are more innovative and tech-savvy, thus overlooking the potential contributions of older employees. Similarly, you might assume that older individuals are wiser or more experienced, dismissing the insights of younger ones. This bias can lead to discrimination and prevent a fair evaluation of individuals’ abilities.

Anchoring Bias
This occurs when your biases are based on the first piece of data you received about a topic. For example, if a used car salesman says a car is $10,000 then he sells it to your ro $8,000, you think you got a $2,000 discount. But you didn’t. He just gave you that $10,000 figure to ‘anchor’ your thoughts, before offering the lower amount to make it sound like a bargain. Really, he was always going to sell it for $8,000.

Attribution Bias
Attribution bias occurs when a person makes an assessment about an argument not based on the consistency of the logic, but rather, the character or situation of the person making the argument. There are many examples of the attribution bias (aka fundamental attribution error) all around us. We may see poor people as lazy or unmotivated so we respect their opinions less, for example.

Authority Bias
Authority bias occurs when you tend to believe people in authority positions because they are an authoritative person, and not because they have a sufficiently logical argument. This occurs, for example, when people might trust their boss because the boss is an authority figure – even if the boss is talking about something they actually know nothing about. Note that this bias can sometimes be valuable if you’re trusting a true expert on a topic, such as trusting your doctor about a medical issue.

Availability Cascade Bias
The availability cascade bias refers to the process by which an idea gains acceptance not due to its intrinsic value or truth, but because of how frequently and widely it is repeated. For instance, a minor incident might be blown out of proportion on social media, leading people to believe it’s a major issue. This bias can result in the spread of misinformation and skew the perception of the importance or truthfulness of a piece of information.

Availability Heuristic Bias
This occurs when you’re more likely to believe or recall information that is most available to you at the time. For example, imagine you were just cleaning your carpet, then, you go outside and realize your car has a smudge on it. Your fist thought might be to get the carpet cleaner because that’s what you were just thinking about! Really, you should be going to the shed to get your car polish. But your brain just went straight to the most recent thing you were thinking about.

Bandwagon Effect Bias
The bandwagon effect bias occurs when you are biased toward believing or accepting something because it’s popular at the time, or everyone else believes it. For example, all your friends may have a certain bias against a certain teacher in your school, so you also take-on that bias, even though you don’t have any first-hand evidence to demonstrate that the teacher is anything but a lovely person.

Base Rate Neglect Bias
Base rate neglect bias is a cognitive bias that happens when you ignore or undervalue the base, or initial, rate of something in favor of new information. For example, you might hear about several shark attacks on the news and consequently overestimate your risk of a shark attack during your beach vacation, even though the base rate of shark attacks is extremely low. This bias can lead to distorted perceptions of risk and probability.

Beauty Bias
Beauty bias is the tendency to favor people who are conventionally attractive. For instance, you might be more likely to hire, trust, or befriend someone because they are good-looking, even if you don’t realize you’re doing it. This bias can lead to unfair advantages for attractive individuals and discrimination against those who are less so, regardless of their skills or qualities.

Confirmation Bias
This occurs when you are likely to believe things that appear to confirm your pre-existing thoughts or opinions on a matter. This prevents you from assessing all new pieces of information in an objective and open-minded manner. For example, sometimes, police are so convinced they have found the perp that they try to make all the new evidence they find fit into their narrative that the suspect is guilty – this has led to many false convictions over time!

Conformity Bias
Conformity bias is the tendency to act or think like the members of a group, even if it contradicts your own judgments or beliefs. For example, you might agree with your friends’ negative opinion about a movie, even though you actually liked it, just because you don’t want to feel left out. This bias can limit independent thinking and lead to decisions that aren’t truly reflective of your preferences.

Cultural Bias
Cultural bias refers to the phenomenon of interpreting and judging others’ behaviors and ideas through the lens of your own cultural background. For example, you might view certain traditions or practices from a culture different than your own as odd or irrational because they are different from what you’re used to. This bias can lead to misunderstanding, stereotyping, and sometimes discrimination against those from different cultures.

Dunning-Kruger Effect Bias
The Dunning-Kruger effect is a cognitive bias where people with low ability at a task overestimate their ability. Essentially, it’s when people think they’re smarter or more capable than they really are. For example, a person who is not well-versed in politics might feel extremely confident in their political knowledge, while in reality, their understanding is limited. This bias can hinder learning and personal growth, as those affected don’t recognize their deficiencies.

Empathy Gap Bias
The empathy gap bias occurs when you underestimate how different emotional states can affect your own or others’ decision-making abilities. For example, when you’re not hungry, you might criticize a friend for overeating at a party, failing to understand how their state of hunger could have influenced their behavior. This bias can lead to misunderstanding and judgment, as it fails to account for the impact of emotions on behavior.

False Consensus Bias
False consensus bias refers to the tendency to overestimate how much other people agree with us. For instance, you might assume that your friends share your political views, when in fact, they might not. This bias can lead to a lack of understanding and respect for diverse opinions, as you may incorrectly assume that your views are the norm.

False Uniqueness Bias
False uniqueness bias is the flip side of the false consensus bias. It refers to the tendency to believe we’re more unique or special than we really are. For example, you might think that you’re the only one at your workplace who cares about maintaining healthy work-life balance, when in reality, many of your colleagues likely feel the same way. This bias can lead to feelings of isolation and can prevent us from connecting with others who share similar experiences or views.

Framing Effect Bias
The framing effect bias is most commonly seen in the media, where media may frame a news item in such a way that they are encouraging viewers to see the issue from a particular perspective. It is also seen in movies, where the filmmaker might frame the story in such a way to make us empathize with one character and loathe another character.

Fundamental Attribution Error Bias
The fundamental attribution error, also known as correspondence bias, is the tendency to overemphasize personal characteristics and ignore situational factors when judging others’ behavior. For instance, if someone cuts you off in traffic, you might think they’re a bad driver or an aggressive person, ignoring the possibility that they might be rushing to an emergency. This bias can lead to misunderstanding and miscommunication, as it doesn’t take into account external factors that influence behavior.

Gambler’s Fallacy Bias
Gambler’s fallacy is the belief that past events can influence future probabilities in random processes. For example, if you’re playing roulette and red comes up ten times in a row, you might think black is “due” and place your bet on it. However, the odds of red or black coming up haven’t changed – each spin is independent of the last. This bias can lead to poor decision-making and potential losses,

Gender Bias
Gender bias is the tendency to prefer one gender over another, leading to unequal treatment. For instance, you might unconsciously believe that men are better leaders than women, leading you to prefer a male candidate over a female candidate for a managerial role, even if they’re equally qualified. This bias can perpetuate gender inequality and limit opportunities for individuals based on their gender.

Halo Effect Bias
The halo effect occurs when someone is initially seen in a positive light, so in all subsequent interactions, you’re inclined to have a bias that favors them. It happens because we seek information that tends to support our initial views, as per the confirmation bias. For example, a teacher may believe one child to be trustworthy, so he gets away with a lot of indiscretions because the teacher will continue to assume the child is trustworthy in all situations.

Hindsight Bias
Hindsight bias refers to the concept that someone think an eventuality that has already occured was obviously going to happen. But these people have the benefit of having already seen the outcome, so they fail to recognize that, in the moment, it wasn’t quite so easy to predict. This occurs, for example, when we smugly deride someone for getting into a car accident, assuming they were reckless when, in reality, there were lots of difficult and unpredictable things happening at the time.

Homophily Bias
Homophily bias, also known as “birds of a feather flock together,” is the tendency to associate and bond with others who are similar to us in terms of socio-economic status, values, and beliefs. For example, you might prefer to spend time with people from your own ethnic group or social class. While this bias can lead to strong social bonds, it can also foster echo chambers and prevent you from understanding and appreciating diverse perspectives.

Illusory Correlation Bias
Illusory correlation bias occurs when you perceive a relationship between two variables that don’t actually correlate. For example, you might associate eating sugar with hyperactivity in children, even though scientific studies have not found a direct causal relationship. This bias can lead to misconceptions and false beliefs, as your perceived associations may not be grounded in factual evidence.

Information Bias
Information bias involves the tendency to seek information, even when it doesn’t affect action. For instance, you might spend hours researching different types of running shoes, even when you’ve already made up your mind about which pair to buy. This bias can lead to information overload and create unnecessary stress, as it involves gathering excessive data that doesn’t contribute to decision-making.

In-Group Bias
In-group bias is a tendency to favor those who are part of your own group, based on shared experiences, characteristics, or identities. It is a subconscious act of favoritism. For example, in a workplace, a manager may give preferential treatment to team members who come from the same hometown, unconsciously overlooking other team members who may be equally or even more deserving of recognition. It’s important to be mindful of this bias, as it can lead to unfair treatment and a lack of diversity in thought and experience.

Just-World Bias
Just-world bias is the belief that the world is inherently fair, leading you to rationalize an otherwise inexplicable event by assigning moral fault to the victim. For instance, if someone loses their job, you might think they must have done something wrong or were not good at their job, ignoring other factors like a company-wide layoff. This bias can lead to victim-blaming and a failure to empathize with others’ misfortunes.

Loss Aversion Bias
Loss aversion bias is often found among wealthy people, whose main focus is on maintaining what they have over anything else. This bias may cause them to miss out on great investment opportunities or to hoard their money unnecessarily. We can also see this in amateur card players, who don’t make their moves in a game out of fear of losing.

Negativity Bias
Negativity bias is a tendency to give more weightage to negative aspects of a situation, rather than equally considering positive ones. For example, if you receive feedback on a project, and despite nine positive comments, there’s one negative comment, you might focus more on the single negative comment, overlooking the positive feedback. This bias often leads people to perceive situations as more negative than they actually are.

Optimism Bias
Some people seem to be naturally optimistic, seeing the good in all situations. These people have what’s called an optimism bias – they’re more inclined to agree with the optimistic rather than pessimistic perspective.

Out-Group Bias
Out-group bias is the reverse of in-group bias, where you harbor prejudice against people who aren’t part of your group. For example, a sports fan might dismiss the skills or performances of players from rival teams, regardless of their actual talent or achievements. Like in-group bias, out-group bias can prevent objective assessment and foster unnecessary division and conflict.

Overconfidence Bias
This bias occurs when people have more confidence in themselves than they should. It might come across as hubris, or even arrogance. Generally, it comes from high self-esteem, or, limited lived experience to be able to predict and look for externalities that can affect outcomes. For example, someone who thinks they have a great sense of direction so don’t check a map may end up lost because they didn’t account for the fact they’re in a city that isn’t a grid system like the one they come from.

Overgeneralization Bias
Overgeneralization bias occurs when you apply one experience to all related situations. For instance, if you have a bad experience with a salesperson at a store, you might assume that all salespeople at that store are unhelpful. This bias can lead to stereotypes and unfair judgments, as it involves making broad conclusions based on limited experiences.

Pessimism Bias
Pessimism bias refers to the inclination to see the pessimistic potential outcome when examining a scenario. This bias, also known as the negativity bias, has been found to be more common in people with anxiety and depression, where they tend to fall into modes of thinking that emphasize the negatives. This can be addressed using cognitive behavioral therapy.

Placebo Effect Bias
The placebo effect bias refers to perceived improvement in condition or performance due to the belief that one has received a beneficial treatment, even when they’ve actually received a placebo, or a treatment with no therapeutic effect. For instance, you might feel more energetic after taking a sugar pill you believe to be a performance-enhancing supplement. This bias can influence the perceived effectiveness of treatments and complicate interpretations of medical research.

Primacy Bias
The opposite of recency bias, primacy bias, occurs when you tend to remember and give more weight to the first pieces of information received. For instance, during a job interview, if a candidate makes a great first impression but subsequently gives mediocre answers, the interviewer might still view the candidate positively due to their initial impression. This bias can lead to incorrect judgments, as the initial information might not be the most accurate or complete representation.

Racial Bias
Racial bias involves making assumptions or holding prejudices against individuals based on their race or ethnicity. For example, if you believe people of a certain race are more likely to be successful or more intelligent than people of another race, you’re exhibiting racial bias. This bias can lead to racial discrimination and reinforce harmful stereotypes.

Recency Bias
Recency bias happens when you place more importance on the most recent information you’ve received, which often leads to a skewed perspective on a situation. For example, consider an employee who performs consistently well throughout the year but makes a minor mistake just before the annual review. If the manager rates the employee lower based on this recent mistake, ignoring their performance for the rest of the year, this would be a clear example of recency bias.

Selection Bias
Selection bias refers to a situation in research where the researcher hasn’t sufficiently selected a sample of research participants, meaning the sample group may be skewed. For example, if a researcher wants to study the political views of a nation, and they only interview people in a rural town, there’s likely to be a more conservative bias as rural places tend to be more conservative on average, meaning the data cannot be sufficiently generalized to the wider population.

Self-serving Bias
The self-serving bias occurs when you are inclined to agree with or support arguments, ideas, or people that will benefit you. For example, you might be subconsciously inclined to agree with or support a sequence of events during a car crash that makes you look like the victim, with blindspots to perfectly reasonable perspectives or explanations that do not position you as the victim.

Status Quo Bias
Status quo bias occurs when you favor the current state of affairs and resist change, even if the change might be beneficial. For instance, an investor might hold onto a non-performing asset because they’re used to it being in their portfolio, even though selling it and buying a more promising asset might be the more rational decision. This bias can inhibit growth and progress, as it prevents you from adapting to new circumstances or taking advantage of better opportunities.

Stereotyping Bias
Simply, a stereotyping bias is when you allow stereotypes about certain people to affect your perceptions of them or what they have to say. Earlier, I gave the example of not respecting the views a poor person because they’re poor. This is a stereotyping bias, where you’re more concerned with a person’s situational factors rather than the truth of what they say or do.

Sunk Cost Fallacy Bias
Sunk cost fallacy bias occurs when you continue a behavior or endeavor based on the already invested resources, such as time, money or effort, disregarding the potential negative outcomes. For instance, imagine you bought a ticket to a music concert but on the day of the event, you fell ill. Instead of resting, you force yourself to attend the concert because you already paid for the ticket. This is a classic example of the sunk cost fallacy – you’re more focused on the initial cost rather than what would be best for you at the present moment.

Survivorship Bias
Survivorship bias happens when you focus on the people or things that have made it past some selection process, while overlooking those that did not, typically because they did not garner attention. For example, if you’re studying successful entrepreneurs, focusing only on those who’ve made it big and ignoring the many more who’ve failed could give you a distorted view of how easy it is to succeed. This bias can lead to overly optimistic beliefs because failures are ignored.

Full List of Biases

Conclusion

Biases affect our decision-making and thinking on a daily basis. They can impact our purchase decisions, feelings toward others, and even feelings about ourselves. By noticing them when they occur, we can reflect on whether they are of service to us, or whether they’re leading to sub-optimal thoughts, behaviors, an decisions.

Further Reading

Eberhardt, J. L. (2020). Biased: Uncovering the hidden prejudice that shapes what we see, think, and do. Los Angeles: Penguin.

Kahneman, D. (2017). Thinking, fast and slow. New York: Penguin Randomhouse.

Priest, H. (2019). Biased: 50 Famous Cognitive Biases That Impair Our Judgment. California: Amazon Digital Services