What Is Belief Bias? | Definition & Examples

Belief bias refers to the tendency to evaluate the strength of an argument based on its plausibility. Instead of considering the validity of the argument itself, we rely on our prior knowledge and beliefs. In other words, if an argument aligns with our beliefs, we tend to accept it.

Belief bias example
You come across the following statement:

“Scientific studies have consistently shown that there is little nutritional difference between organic and conventional foods.”

Because you firmly believe that an all-organic diet is superior to a conventional one, you are skeptical and quickly dismiss the argument, even though it provides scientific evidence.

As a result of belief bias, we often fall for “believable” arguments and reject “unbelievable” ones without properly examining whether they are valid.

What is belief bias?

Belief bias is a cognitive bias that causes us to judge the validity of a claim or conclusion based on how believable we find it. With belief bias, our knowledge about the world influences how we evaluate arguments. This leads us to accept arguments as true because they make sense to us (i.e., they are believable), and not because they are logically valid.

Belief bias occurs in the context of syllogistic reasoning. A syllogism is a type of deductive argument consisting of two premises and a conclusion that follows from the premises (e.g., “All men are human; all humans are mortal; therefore, all men are mortal”). A deductive argument moves from the general to the specific, and it is logically valid only when both premises are true.

For example, consider the following argument: “All flowers have petals; daffodils have petals; therefore, daffodils are flowers.” Most people would find this argument acceptable because everyone knows that daffodils are flowers.

However, the argument is logically unsound because not all flowers have petals. Due to belief bias, most of us would readily accept the conclusion because it aligns with what we know and overlook the fact that the first premise (“all flowers have petals”) is wrong.

Why does belief bias occur?

Belief bias is a consequence of our reasoning process. On the one hand, we try to apply the rules of logic, and, on the other hand, we tend to incorporate prior beliefs into our judgments and inferences.

Relying on prior knowledge or beliefs can be helpful when we are faced with unfamiliar situations in our everyday lives. However, it can be detrimental in cases where the goal is to assess the validity of an argument (e.g., in a court of law). In such cases, relying on what we already know gives rise to belief bias.

Belief bias is a complex phenomenon. Some of the factors that play a role in it include:

  • Deeply held convictions. Belief bias is especially strong when people are convinced that their values, opinions, or feelings are “right.” This is often the case with emotionally charged topics, like religion or politics.
  • Obscure arguments. People tend to be more receptive to arguments that support their beliefs when they don’t know much about the topic. The same happens when someone puts forth an argument that we cannot follow. As long as the conclusion matches our beliefs, we are more likely to accept it, even if the argument makes no logical sense to us.
  • Time pressure. When people are asked to evaluate arguments in a limited amount of time, they are more likely to display belief bias. Relatedly, more processing time is more likely to yield logical evaluations. Avoiding belief bias involves coming up with alternative premises to a conclusion, which can be time consuming.

Belief bias example

Belief bias causes us to accept a conclusion and overlook whether the premises logically lead to that conclusion. In politics, belief bias can interfere with the rational evaluation of policy proposals.

Belief bias and political views 
Let’s say that you support the idea that illegal immigration should be stopped. You hear a politician claim the following during an interview:

“Illegal immigrants cause a large number of crimes. For this reason, they will be separated from their children at the border. This will ultimately lead to a decrease in the number of illegal immigrants.”

Because the conclusion is in line with your beliefs, you focus on this and accept the argument. However, it’s also important to evaluate how the premises relate to each other and the conclusion before accepting an argument. Here, the decrease in illegal immigrants does not logically follow from the premises. Moreover, the first premise is vague and not supported with evidence.

How to avoid belief bias

Like with other forms of bias, avoiding belief bias can be challenging because we naturally evaluate information according to our preexisting knowledge. However, there are a few steps you can take to minimize its influence:

  • Become aware of your bias. Learning about belief bias and acknowledging that everyone has preexisting beliefs that can cloud their judgment is the first step in overcoming belief bias.
  • Consider alternative viewpoints. Before making up your mind, actively seek out different opinions that challenge your beliefs. Engaging with different perspectives can help you understand the complexity of an issue and limit belief bias.
  • Evaluate all arguments objectively. Instead of dismissing arguments that don’t align with our beliefs, we need to consider the validity of an argument based on its logic and evidence.
  • Slow down your thinking. Take your time to carefully evaluate information rather than relying on gut reactions that are influenced by your beliefs. Reflect on whether your preexisting beliefs could be influencing your reasoning.

Other types of research bias

Frequently asked questions

What is the difference between belief bias and belief perseverance?

Belief bias and belief perseverance are both cognitive biases that affect our critical thinking and decision-making, but they refer to different phenomena.

  • Belief bias describes people’s tendency to evaluate arguments based on whether the conclusion aligns with their preexisting beliefs.
  • Belief perseverance is the tendency to maintain one’s initial ideas or beliefs in spite of new and compelling evidence that disproves them.

In other words, belief bias refers to how we evaluate arguments based on our existing beliefs, whereas belief perseverance refers to the persistence of those beliefs in the face of contradictory information.

What is the difference between belief bias and confirmation bias?

Belief bias and confirmation bias are both types of cognitive bias that impact our judgment and decision-making.

Confirmation bias relates to how we perceive and judge evidence. We tend to seek out and prefer information that supports our preexisting beliefs, ignoring any information that contradicts those beliefs.

Belief bias describes the tendency to judge an argument based on how plausible the conclusion seems to us, rather than how much evidence is provided to support it during the course of the argument.

Sources in this article

We strongly encourage students to use sources in their work. You can cite our article (APA Style) or take a deep dive into the articles below.

This Scribbr article

Nikolopoulou, K. (2023, October 07). What Is Belief Bias? | Definition & Examples. Scribbr. Retrieved July 17, 2024, from https://www.scribbr.com/research-bias/belief-bias/


Trippas, D., Kellen, D., Singmann, H., Pennycook, G., Koehler, D. J., Fugelsang, J. A., & Dubé, C. (2018). Characterizing belief bias in syllogistic reasoning: A hierarchical Bayesian meta-analysis of ROC data. Psychonomic Bulletin & Review, 25(6), 2141–2174. https://doi.org/10.3758/s13423-018-1460-7

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Kassiani Nikolopoulou

Kassiani has an academic background in Communication, Bioeconomy and Circular Economy. As a former journalist she enjoys turning complex scientific information into easily accessible articles to help students. She specializes in writing about research methods and research bias.