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Types of Bias

Last updated on 20th April 2023

Bias is an inclination, prejudice, preference or tendency towards or against a person, group, thing, idea or belief. Biases are usually unfair or prejudicial and are often based on stereotypes, rather than knowledge or experience. Bias is usually learned, although some biases may be innate. Bias can develop at any time in an individual’s life.

Bias is a uniquely human attribute. In some cases, the bias may be subconscious, and the individual may not be aware that they are experiencing bias towards others. Although biases can sometimes be positive or helpful to the individual, in the majority of cases, biases will be negative or damaging.

Bias is usually based on stereotypes relating to the physical characteristics of an individual or the group they identify with. These characteristics are often immutable, meaning they do not change over time.

The most common biases are based on characteristics such as:

  • Race.
  • Ethnicity.
  • Gender.
  • Religion.
  • Sexual orientation.
  • Socioeconomic background.
  • Educational background.

One of the biggest effects of bias is prejudgement, which can result in discriminatory practices. As some biases can be helpful and are used in heuristic decision-making, it is important to find the balance between helpful biases and negative, prejudicial biases.

It can be almost impossible to be completely unbiased. It is a natural human instinct to make judgements based on first impressions and pre-conceived ideas or knowledge. However, by being aware of these judgements and ensuring biases are not unconscious, we can avoid the harmful stereotyping and discriminatory practices that often result from biases. For more information on discrimination, consult our knowledge base.

Gender bias

How many types of bias are there?

There are hundreds of different types of bias that have been identified. These different categories of bias have multiple bias examples within them. Let’s take a look at the main different types of bias.

Cognitive bias

This is the most common type of bias. Research suggests that there are more than 175 different types of cognitive bias. It refers to deviation from standards of judgement whereby you may create inferences, assessments or perceptions that are unreasonable. You may also recollect past experiences incorrectly. These perceptions may dictate a person’s behaviour or attitude, either in a positive or negative way.


A prejudice is a prejudgement or prior opinion that a person makes before they are given the relevant facts and information. When a prejudice takes place, this prejudgement is usually negative or unfavourable. Prejudices are usually based on factors such as race, religion, gender, sexual orientation, age, disability, social class or language.

Contextual bias

This refers to when experts who have good intentions are vulnerable to making incorrect decisions, based on external influences or influences that are irrelevant or unrelated to the situation. This can result in a loss of objectivity and can cause the experts to develop subconscious expectations.

Contextual biases can be found in academia, research, forensic analysis, publications and court situations. Contextual bias can also occur in the media. It can influence how stories are selected and reported.

Contextual biases are most commonly reported in law enforcement. Racial profiling and victim-blaming are both examples of common contextual biases. reported that in 2019/2020, there were 6 Stop and Searches for every 1,000 White people, compared to 54 Stop and Searches for every 1,000 Black people. This means Black people were 9 times more likely to be stopped by law enforcement than white people.

Unconscious or implicit bias

This is related to implicit stereotypes and is when you unconsciously attribute certain qualities to certain social groups. This can then influence your perceptions, attitudes and behaviour towards this social group. There are many different types of unconscious bias. We will look at some examples of unconscious bias later.

Statistical bias

This is related to the process of data collection. Statistical bias can affect the way a research sample is selected or the way that data is collected. It can result in misleading results that differ from the accurate representation. Statistical bias examples include forecast bias, the observer-expectancy effect, selection bias, reporting bias and social desirability bias.

Bias against race

What are the two main types of bias?

There are two main types of bias to be aware of, conscious bias and unconscious bias.

Conscious bias

Conscious bias is sometimes known as explicit bias. This is a type of bias that you are aware of. The bias is happening consciously, in that you know you are being biased and are acting with intent. An individual with conscious bias is likely to be explicit with their beliefs and attitudes and behave with clear intent.

The biased attitudes and behaviours are processed at a conscious level. A conscious bias that is extreme is usually characterised by negative behaviour, such as physical or verbal harassment. It can also manifest as exclusionary behaviour.

Conscious biases are prejudices. They usually discriminate against people or groups of people. There is usually malicious intent involved in conscious biases.

Unconscious bias

Unconscious bias is also known as implicit bias. It is a very different bias than conscious bias for several reasons. Unconscious biases are beliefs and attitudes that operate outside of a person’s awareness and control. Unconscious bias can be in direct contrast with the beliefs and values you think you hold. You may not even be aware that you hold these biases, or that they are affecting your attitudes and behaviours.

Unconscious biases are difficult to identify. They may influence your actions and behaviours more than conscious biases, without you realising it. Unconscious bias usually involves no malicious intent, as a person may be unaware of their bias and the effect it is having. We will look more at unconscious bias later.

What is cognitive bias?

Cognitive biases are repeated, systematic errors of thinking that occur when you misinterpret information in the world around you. Cognitive biases can affect the rationality of your judgement and can lead you to make inaccurate or unreasonable conclusions or decisions.

Cognitive bias was first reported by Tversky and Kahneman (1972) who investigated how people made decisions with limited resources or information. They reported violations or deviations from the norm when people rely on cognitive biases.

Cognitive biases are unconscious and usually automatic. They often occur when people are making quick decisions. However, cognitive biases often cause these decisions to be less accurate.

Cognitive biases can be caused by a number of things, including:

  • Mental shortcuts (also known as Heuristics) that the brain uses to make decisions or judgements.
  • Flawed memory.
  • Your brain’s attempt to simplify information.
  • Issues with paying attention.
  • Emotional input.
  • Social pressures.
  • Ageing.

These factors can all cause cognitive bias and can affect an individual’s decision-making in multiple areas of their life. Indeed, cognitive bias has been reported in areas such as education, healthcare, recruitment, business, finance, management, social behaviour and cognition.

In some situations, cognitive bias can be positive. It can help you to make quicker or more optimal decisions at times when all the information is not available, or a fast decision is needed. However, in many cases, cognitive biases cause you to misinterpret information and come to an inaccurate conclusion. This can lead to poor decisions or misjudgements.

Affinity bias people have the same interests

How many types of cognitive bias are there?

As mentioned earlier, there are as many as 175 different types of cognitive bias. However, some of these cognitive biases occur more frequently than others. Some types of cognitive biases are social, some are related to memory and others affect the formation of beliefs, decision-making and behaviour. Some of the most common cognitive biases are listed below.

Actor-observer bias

This is a type of social cognitive bias. It relates to the differences between how we explain our behaviour vs how we explain other people’s behaviour. People have a tendency to attribute their own actions to external causes or factors, rather than their own personality or actions. In contrast, people usually explain the behaviour of others by overemphasising the influence of their personality or behaviour and underemphasising situational or external factors. This type of bias particularly occurs when the outcomes of a situation are negative.

Anchoring bias

Anchoring bias is the tendency to heavily rely or “anchor” on the first piece of information you learn or on one specific trait. In other words, the first piece of information you learn will have a more substantial impact on your judgement than any other information you learn at a later time.

Attentional bias

This relates to the practice of paying attention to some things while simultaneously ignoring other things. Although attentional bias can help us focus on the pieces of information that are most important, it can also cause you to disregard other information because of your biases.

Availability heuristic

This is the tendency to overestimate the likelihood of events or have greater trust in ideas that come to mind more easily or are more available in your memory. This could cause you to think certain judgements are correct or overestimate the probability of an event occurring. Information that is easily accessible in your memory can seem more reliable.

Confirmation bias

This involves favouring or focusing on information that confirms your existing beliefs and preconceptions. You may automatically discount information that does not confirm your bias.

Dunning-Kruger effect

This is the inability to recognise your own incompetence. People may believe they are more intelligent or capable than they actually are or overestimate their own abilities.

False consensus effect

This is the overestimation of how much other people agree with you or approve of your behaviour.

Functional fixedness

This is the limitation of only seeing objects as working in a particular way. Functional fixedness can also be applied to people in that you may only be able to think of them in the role you are used to.

Halo effect

This involves the way you think or feel about a person being shaped by one characteristic. This one positive or negative trait can influence how their other qualities or characteristics are rated. The halo effect most commonly relates to physical attractiveness.

Misinformation effect

This is when your memory of an event is altered or becomes less accurate because of misinformation you receive after the event. Post-event information interferes with the original memory.

Optimism bias

This is the tendency to be over-optimistic and overestimate the likelihood of you achieving favourable outcomes and success and underestimate the likelihood of you experiencing unfavourable outcomes, misfortune or hardships.

Self-serving bias

This is the tendency to blame outside forces if something bad happens and take responsibility when good things happen.

Diverse business team

What is unconscious bias?

Unconscious bias is also known as implicit bias. It relates to subconscious attitudes or beliefs that affect the way that individuals think, feel and behave towards other people. Unconscious biases are often formed in childhood and can be formed through familial, social and educational environments.

Unconscious stereotypes are often based on learned associations between particular qualities and social groups. This could include associations related to race and gender.

Unconscious biases are formed outside of a person’s conscious awareness. They can have a significant impact on our attitudes and behaviours towards other people. Unconscious biases can have a particular effect on decision-making and behaviour when quick decisions are required or when an individual is in a stressful situation. Unconscious biases can contribute to inequality.

Unconscious bias often causes you to unconsciously attribute certain qualities to individuals who belong to certain groups.

There are a number of factors that can contribute to the creation of unconscious biases, including your background, personal experiences and history, and societal stereotypes. For more information on unconscious bias, consult our knowledge base.

How many types of unconscious bias are there?

There are many different types of unconscious bias. Below are the most common types of unconscious bias.

Affinity bias

This refers to the unconscious preference of people who share qualities with you or are similar to you. You may be more likely to connect with people who have similar interests, experiences and backgrounds to you.

Attribution bias

This relates to how you perceive your own actions compared to the actions of others. This particularly relates to how you perceive success and failure. Our accomplishments are a result of skill or internal traits whereas failure is a result of external forces. People are more likely to undervalue the accomplishments and overvalue the mistakes of others.


This refers to having negative feelings towards someone or discriminating against them based on their age. Age UK reported that 36% of over 50s reported feeling disadvantaged at work because of their age. Ageism tends to be directed more frequently at women compared to men.

Beauty bias

This is the belief that attractive people are more successful, competent and qualified than unattractive people. A person’s physical appearance is used as a judgement of their character of competency.

Confirmation bias

This is the tendency of selective observation, whereby you search for evidence that backs up your opinion and overlook or reject information that may contradict your opinion. You are creating opinions based on your own beliefs, desires and prejudices.

Conformity bias

Conformity bias is when your views are influenced or changed by the views of others. This is related to peer pressure and can cause you to seek acceptance and act similar to others, regardless of your own beliefs.

Contrast effect

This is when you assess two or more things by comparing them to each other, rather than assessing them based on their merit. This can cause you to exaggerate the positives of one thing and the negatives of another.

Gender bias

This refers to a preference for one gender over the other. Gender bias is usually a result of an individual’s ingrained beliefs about gender roles and stereotypes.

Unconscious bias

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About the author

Nicole Murphy

Nicole Murphy

Nicole graduated with a First-Class Honours degree in Psychology in 2013. She works as a writer and editor and tries to combine all her passions - writing, education, and psychology. Outside of work, Nicole loves to travel, go to the beach, and drink a lot of coffee! She is currently training to climb Machu Picchu in Peru.

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