Confirmation Bias

You may know someone who believes she can predict the sex of a baby by suspending a wedding ring on a string over a pregnant woman’s abdomen. This person may even be a relative, and you may have grown up hearing stories about her uncannily accurate predictions. Perhaps other family members are fond of listing, by way of proof of her talent, the times she has been correct in her predictions. You may have noticed that her success with babies born within your memory has been in keeping with the law of averages. In other words, she is right about half the time. In light of this rather unimpressive track record, you might have been puzzled when her failures did nothing to shake her faith, or the faith of other family members, in her abilities. She, and others, may even recall incorrectly that she was right at times that she was clearly wrong, and use those occasions as further proof of her accuracy. If this sounds familiar, your relatives are exhibiting a confirmation bias.

What is Confirmation Bias Theory?

A confirmation bias is a way of viewing the world selectively. People with a confirmation bias notice those things that reinforce what they already believe. They may disregard anything that tends to contradict their beliefs. Some people may even go so far as to recall events or data incorrectly, remembering them in such a way that the information supports their original theory. Sometimes, a confirmation bias can be more subtle. People who believe that men are not nurturing may ignore or rationalize examples of men who are behaving in a nurturing way. However, those who live in a sub-culture in which few men are nurturing because the culture discourages such behavior may not ignore examples that contradict their belief that men are not nurturing. For them, confirmation bias can manifest itself as a failure to look for examples of nurturing men.

One reason it is very easy to succumb to a confirmation bias is that people tend to overvalue those things that confirm their pet beliefs. Information that supports an established conclusion is easier to assimilate. It is much easier to fail to notice evidence against a strongly held hypothesis. Although people are most susceptible to confirmation bias when their beliefs are based on prejudices or folk tales, confirmation bias can creep into research and destroy the objectivity of investigators, tainting research and destroying careers.

Most commonly, when confirmation bias contaminates research, it does so in the form of faulty research design or misinterpretation of the results. To avoid this problem, research methods are carefully taught to students who will conduct research as part of their education or in their future careers. Researchers are also taught to be proactive in their attempts to refute their own theories.

Origins of Confirmation Bias Theory

Scholars from at least as long ago as the Ancient Greek Thucydides have noticed and remarked upon the human tendency to develop and nurture confirmation bias. However, the concept was not formalized into a hypothesis and subjected to testing until British psychologist Peter Wason named the phenomenon and made it the subject of his research in 1960.

Wason was a proponent of falsificationism, meaning that he believed that the best way to prove a theory was to make an honest attempt to prove it false. Because he looked at scientific investigation from this standpoint, to him the tendency displayed by the participants in his studies appeared to be a preference for information that confirmed a previously held belief. He saw their responses as a preference for confirmation of an existing belief over information that would cast doubt on that belief. As a result, he called his observation a confirmation bias.

Criticisms of Confirmation Bias Theory

In 1987, researchers Joshua Klayman and Young-Won Ha took issue with the way Wason interpreted what he observed. They reexamined Wason’s claims using a different standard for testing hypotheses and concluded that Wason’s studies had shown a confirmation bias as a result of the particular way in which his studies were conducted. Their own studies, which were modified slightly to eliminate the perceived problem, demonstrated a much less pronounced confirmation bias.

As a result of Klayman and Ha’s research, as well as the research of others, research in this area has shifted focus from an attempt to determine whether people choose confirmation rather than falsification when given the choice, to a broader look at how people examine their own theories and decide whether they are valid. One prominent question has become whether people check their own beliefs in an informative way or utilize an informative approach that is also positive. As a result, investigators have learned a great deal more about how people process information and which information they choose to consider as part of that processing.