Most of us would love to believe that we have open minds, ready to change our opinions as we take in new information. On the contrary, our brains are wired to hold onto our first impressions for dear life. Confirmation bias is what causes us to seek out and embrace information that confirms our preexisting beliefs and ignore the rest, rather than weigh each piece of evidence equally.
This happens in every facet of life, from the social, such as the way your first impression of someone colors the way you see their every action, to the professional, like the way a doctor may stick to a first diagnosis of a patient even if not all of the symptoms match that conclusion.
The good news is that once you know this bias is likely to happen, you can take steps to avoid it. One way to counteract confirmation bias is to consciously look for evidence that disproves your beliefs. A 2011 study in Psychological Medicine found that when psychiatrists were asked to make a preliminary diagnosis of a patient and then perform an online search, those who were asked to search for information to confirm their decision made the wrong final diagnosis 70% of the time versus only 27% for those looking for information to prove it wrong. Learn more about this and other cognitive biases with these videos.