Confirmation Bias: No Need To Test My Hypothesis


Oftentimes when a student is asked to write a research paper, they primarily search for information that would confirm their beliefs on the topic. The student might fail to fully consider information that is inconsistent with their beliefs. For example, if the student is writing a research paper that focuses on the positive aspects of parents co-sleeping with their children, the student might ignore research that suggests there are negative consequences to parents sleeping in the same bed as their child.  


One explanation as to why the student is inclined to search for information that confirms their preexisting beliefs is because when people would like a certain idea/concept to be true, they end up believing it to be true. This means that rather than searching through all the evidence, the individual may focus solely on the information and evidence that supports their hypothesis. This type of cognitive error is known as confirmation bias. 

Definition of Confirmation Bias

Confirmation bias is the inclination to seek, interpret, prefer, and/or recall information in a manner that confirms one's preexisting beliefs or biases.


In an experiment he published in 1960, Peter Wason, an English Psychologist, coined the term “confirmation bias.” In this experiment, the participants were told by the experimenter that they would be given “three numbers which conform to a simple rule that [he has] in mind.” Then, the participants were asked to write down sets of numbers they believed conformed to this rule while receiving feedback from the experimenter on whether the numbers conformed or not. The participants were allowed to repeat this procedure until they came up with a hypothesis of what they believed the rule to be. Surprisingly, more than half of the subjects were unable to determine the rule as they only tested numbers that conformed to their original hypothesis. Furthermore, they were unwilling to test examples of numbers that went against their initial hypothesis. Wason coined this as “confirmation bias” since the participants tested their ideas in a one-sided way, focusing on one possibility and ignoring alternatives.

Why Care?

Confirmation bias can impact people’s views on social issues such as politics, religion, women's rights, race, capital punishment, climate change, vaccinations, immigration, war, and other important topics. For this reason, it is crucial that you consider alternative explanations, especially in ingrained, ideological, or emotionally charged views (such as the topics previously listed), since confirmation bias is most pronounced in these cases. These psychological tendencies are especially important to consider when you are fighting for a cause; instead of just following what you hear in the media or relying solely on your beliefs or those of others, you can fully research all aspects of the topic and inform yourself. Not only will you gain new knowledge regarding the cause, but you can also use what you have learned as a tool to persuade others and as a shield to prevent people from being convinced of fallacies that may be solely based on the beliefs, ideas, and biases of others.

Think Further

  1. Can you think of one belief that your parents/caregivers instilled in you since you were a young child? Do you believe there is anything that someone else can say that will change the way you think?
  2. When discussing a topic that you feel strongly about do you get defensive or do you hear the other person out? Do you consider alternative explanations to what you believe?
  3. Think of a time when you were certain you had the best explanation for something but discovered a more reliable explanation after doing some research. What convinced you that the other explanation was more powerful than yours?


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Learn More

  1. Confirmation Bias And the Power of Disconfirming Evidence. (2018, October 02). Retrieved from
  2. Plous, Scott (1993), The Psychology of Judgment and Decision Making, p. 233
  3. Nickerson, Raymond S. (June 1998), “Confirmation Bias: A Ubiquitous Phenomenon in Many Guises”, Review of General Psychology, 2 (2): 175–220, doi:10.1037/1089-2680.2.2.175
  4. More nuanced view of Wason’s experiment: Klein, G. (2019). The Curious Case of Confirmation Bias.