Abstract
Having a confirmation bias sometimes leads us to hold inaccurate beliefs. So, the puzzle goes: why do we have it? According to the influential argumentative theory of reasoning, confirmation bias emerges because the primary function of reason is not to form accurate beliefs, but to convince others that we’re right. A crucial prediction of the theory, then, is that confirmation bias should be found only in the reasoning domain. In this article, we argue that there is evidence that confirmation bias does exist outside the reasoning domain. This undermines the main evidential basis for the argumentative theory of reasoning. In presenting the relevant evidence, we explore why having such confirmation bias may not be maladaptive.
Highlights
Across a wide variety of experiments, subjects exhibit a confirmation bias, “the seeking or interpreting of evidence in ways that are partial to existing beliefs, expectations, or a hypothesis in hand” (Nickerson 1998, p. 175)
Confidence measures, on the other hand, changed significantly: despite having the same performance in both conditions, the rats were willing to wait significantly longer in the high positive evidence condition, compared to the low positive evidence condition. It seems that even non-human animals have a confirmation bias when computing levels of confidence in their perceptual decisions: they disproportionately rely on positive sensory evidence, and tend to ignore sensory evidence contradicting their decision. These results strongly suggest that the computations underlying both perception and perceptual confidence are influenced by a positive evidence bias, i.e. an over-reliance on evidence supporting one’s decision, analogous to a form of confirmation bias in these domains
The recognition of confirmation bias outside the reasoning domain could spark a revolution in the way in which confirmation bias is studied
Summary
The best evidence against the argumentative theory would come from evidence that confirmation bias exists (a) in at least one non-reasoning domain, and (b) in animals other than humans. We argue that both of these possibilities are well established in the literature
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