Confirmation bias is often described as a result of automatic, unintentional strategies rather than deliberate deception.[15][84] According to Robert MacCoun, most biased evidence processing occurs through a combination of both "cold" (cognitive) and "hot" (motivated) mechanisms.[85]
Cognitive explanations for confirmation bias are based on limitations in people's ability to handle complex tasks, and the shortcuts, called heuristics, that they use.[86] For example, people may judge the reliability of evidence by using the availability heuristic—i.e., how readily a particular idea comes to mind.[87] It is also possible that people can only focus on one thought at a time, so find it difficult to test alternative hypotheses in parallel.