Chapter 6
Lesson 12: Confirmation Bias and Social Cognition
Why do coincidences lead us to make incorrect conclusions? For instance, why would someone who saw a news report about a plane crash only hours after dreaming of one explain the coincidence as a case of precognition? The reason is that our prior beliefs--our preconceptions (see Lesson 4)--cause us to pay attention to particular conjunctions of events and to interpret them in particular ways. In fact, we tend to pay close attention to or seek out information that verifies (confirms) our preconceptions, and to ignore, distort, or avoid information that falsifies (disconfirms) our preconceptions, a tendency that is called the confirmation bias.
In order to illustrate the confirmation bias, let's look at the self-verification motive, which was discussed in Chapter 5. The self-verification motive is one important expression of the confirmation bias in all people: it causes us to pay close attention to or seek out any information that verifies our self-image and to ignore or avoid information that falsifies it. In those who have many negative self-beliefs, the confirmation bias leads them to pay close attention to failures and setbacks, and to become friends with others who have a negative view of them. It also leads them to downplay any successes they have experienced, and to avoid others who think well of them. Lastly, experiences that are ambiguous (that is, experiences of uncertain meaning) will tend to be perceived and remembered by these people in ways that are consistent with their negative self-image.
The confirmation bias also can have adverse effects in therapeutic situations. For example, let's say that a physician has referred a patient to a clinical psychologist. The physician told the psychologist that the patient often feels fatigued and has difficulty concentrating, but appears to have no physical illness that could explain these symptoms. Based on this brief description, the psychologist immediately concluded that the client probably has "major depression," which is a mental disorder characterized by symptoms such as sadness, loss of the ability to feel pleasure, increased anxiety, difficulty sleeping, a loss of appetite, problems with concentration, and so on. When the well dressed, clean-shaven, and alert-looking client came to see the psychologist, she didn't notice that he was well dressed or clean-shaven (which would have counted against a diagnosis of depression), and she interpreted his alert look as a sign of anxiety (which is consistent with depression). The psychologist asked the man the following questions:
- Do you often feel sad?
- Do you sometimes have trouble sleeping?
- Are you having trouble in your relationships?
- Are there some activities you once enjoyed that no longer seem fun?
- Have you ever thought that others would be better off if you weren't around?
He answered no to the first question; but then the psychologist remembered that many depressed people often deny feeling sad. He answered yes to the question about sleep problems, which supports the diagnosis of depression. He answered yes to the question about relationship difficulties, which supports a diagnosis of depression. He stated that he no longer enjoys some activities that he used to enjoy, which again supports a diagnosis of depression. Finally, he answered yes to the last question, which clinched the diagnosis of depression for the psychologist since it implied that the man has thought about committing suicide.
Can you see the problem here? It seems that the clinical psychologist asked only those questions that would tend to confirm her prior belief that the man has major depression Furthermore, the questions she asked could be answered in the same way by nondepressed people. Most important, she asked no questions that would easily disconfirm her belief. In fact, when the man stated that he was not feeling sad, this was reinterpreted by the psychologist as support for the diagnosis of depression. She also did not notice aspects of the man's physical appearance that contradicted a diagnosis of depression; and she interpreted ambiguous behavior (alertness) as a symptom of depression. Thus, the confirmation bias led the psychologist to look for evidence in support of her prior belief that the man was depressed, and to ignore or reinterpret evidence against the belief.
In general, the confirmation bias serves to maintain and strengthen beliefs we already hold by causing us to perceive and remember experiences that support these beliefs, and to ignore or reinterpret those that don't. Over time, our beliefs appear to us to be so well confirmed that we come to think of them as "obviously true." We don't realize, however, that our own bias towards seeking out confirming evidence is the reason why our preconceptions seem to be so obvious.
Person Perception, Prejudice, and the Confirmation Bias
Person perception can be defined as a set of automatic mental processes used to assign personal characteristics (such as motives, traits, attitudes, and emotional states) to others. Whenever we first meet someone, we immediately engage in person perception, which is often based (at least initially) on relatively superficial characteristics such as physical appearance, mannerisms, and facial expressions. Thus, we immediately begin to form beliefs about the personal characteristics of others (a "first impression") as soon as we first see or hear them. At this point, the confirmation bias typically begins to have an influence: we tend to seek out information that will verify our beliefs, thereby becoming more convinced that they are true. For example, prejudiced people will have negative preconceptions (stereotypes) about members of the group that is the target of their prejudice. When meeting individuals who appear to be from that group, prejudiced people will pay close attention to and remember information consistent with their stereotypes, and will ignore or distort information inconsistent with them. Thus, contact between individuals with prejudiced attitudes towards each other may serve only to strengthen the prejudice: the confirmation bias will lead them to find evidence in support of their prejudice, and to ignore or distort evidence against their prejudice.
Reducing the Effects of the Confirmation Bias
No one is immune to the confirmation bias. In fact, according to Mahoney (1977), even scientists are prone to the confirmation bias in their daily work:
One study found that the vast majority of scientists drawn from a national sample showed a strong preference for "confirmatory" experiments.... Over half of these scientists did not even recognize disconfirmation ... as a valid reasoning form! In another study the logical reasoning skills of 30 scientists were compared to those of 15 relatively uneducated Protestant ministers.... Where there were performance differences, they tended to favor the ministers. Confirmatory bias was prevalent in both groups, but the ministers used disconfirmatory logic almost twice as often as the scientists did.
This passage suggests that the confirmation bias is so strong in most people that it is very difficult to avoid its effects, even in those who we think should know better. It also suggests a way to minimize its effects: in order to reduce the confirmation bias, we must try to falsify our preconceptions. That is, we must try to find evidence that would show our beliefs to be wrong, as Karl Popper instructed (Lesson 7). For example, if you are a woman and you believe that "all men are 'pigs'," such a belief will affect your conversation during a first date with a man. The confirmation bias will lead you to ask questions such as: "what is the worst thing you ever did to someone you were going out with?" The answers to such questions will only serve to strengthen your prejudice against men. In order to reduce the confirmation bias, you need to attempt to falsify your preconceptions about men by asking questions such as: "what would you want to do to make the world a better place?" By asking such questions, you are more likely to receive answers that would cause you to modify your negative stereotypes about men.
Critical Thinking Questions
Question 12-1
For the example in which the clinical psychologist was trying to determine whether her client had major depression, write a list of questions that she could have used if she had wanted to reduce the influence of the confirmation bias on her thinking.
Suggested Answer
Question 12-2
Let's say that you are asked to look at four cards laid out on a table (Schick and Vaughn, 2002). On one side of each card is a letter and on the other side is a number. You are able to see the following letters and numbers on the cards:
You are asked to test the following claim: "if a card has a vowel on one side, it has an even number on the other." Which cards would you need to turn over in order to test this claim?
Suggested Answer
Question 12-3
In the textbook's discussion of persuasion, it was mentioned that, when trying to persuade others to adopt a particular side of an issue, sometimes it is best to provide an argument that discusses both sides of the issue and, at other times, it is best to provide an argument that discusses only one side of the issue. Based on what you have learned in this lesson, in what kind of situation might it be better to provide a one-sided argument? Explain your answer.
Suggested Answer
Question 12-4
Look at the following numbers: 2, 4, 6. This sequence of numbers follows a particular rule (Schick & Vaughn, 2002). List all of the possible rules that this sequence of numbers could be following. For each possibility, list three other numbers that would allow you to test whether or not the sequence actually is following that rule.
Suggested Answer
Bibliography and References
Carroll, R. T. (2002). Confirmation bias. Skeptic's Dictionary. Retrieved May 27, 2002, from
Levy, D. A. (1997). Tools of critical thinking: Metathoughts for psychology.Boston: Allyn & Bacon.
Mahoney, M. J. (1977). Publication prejudices: An experimental study of confirmatory bias in the peer review system. Cognitive Therapy and Research, 1(2) 161-175. Retrieved May 26, 2002, from
Ricker, J. P. (2002). An introduction to the science of psychology.Boston: Pearson Custom Publishing.
Schick, Jr., T., & Vaughn, L. (2002). How to think about weird things: Critical thinking for a new age (3rd ed.). Boston: McGraw-Hill.