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Confirmation bias
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Confirmation bias

In statistical inference, confirmation bias is a type of cognitive bias towards confirmation of the hypothesis under study. See also bias (statistics). To compensate for this natural human tendency, the scientific method is constructed so that we must try to disprove our hypotheses. See falsifiability.

In psychology, confirmation bias is a phenomenon whereby, in a variety of settings, decision makers have been shown to notice more, assign more weight to, and actively seek out evidence that confirms their claims and they tend to ignore and not seek that which might discount their claims. As such, it can be thought of as a form of selection bias in collecting evidence.

In one classic experiment, subjects were shown the hypothesis that "If a card has a vowel on one side, it must have an even number on the other side" and four large cards, that looked something like:

E 4
7 K

Subjects were then asked which two cards they would turn over to test the rule.

Almost all experimental subjects did not choose the correct two cards, which would be E (via modus ponens) and 7 (via modus tollens). Most chose E and 4, committing the logical fallacy of affirming the consequent, and choosing a test that might confirm but which could never falsify the hypothesis.

It should be noted, however, that studies that used more concrete concepts showed very different results. In one study, students had no trouble with a version of the cards experiment in choosing "Beer" and "16" testing the hypothesis that "People who drink beer must be at least 21 years old."

Some have argued that confirmation bias may be the cause of self-perpetuating and self-fulfilling social beliefs.

In addition, many legal and political systems depend on adversarial relations in order to achieve just decisions despite the biases of the parties. In these systems it is assumed that it is beyond the ability of a single human being to avoid confirmation bias, and hence the systems are in place so that different biases work against each other.

Decision makers should consider opposing views and try to think about why they might be wrong in order to reduce overconfidence effects.

This bias may occur at least partially because negatives are inherently more difficult to process mentally than positives.

See also: disconfirmation bias, expectancy effect, list of cognitive biases.

References

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