Confirmation bias is a type of cognitive bias which causes people to favor evidence that confirms their pre-existing beliefs over evidence that would tend to disprove it. This often occurs subconsciously, and the individual doesn't realize it has happened. Some examples would be:
- God answers prayers - A person remembers each time a prayer appears to have been answered, and dismiss any times it hasn't, often with the excuse, "God always answers prayer - sometimes, he says no".
The primary problem with confirmation bias is that it leads to people having warped or "filtered" understandings of the world around them. This can support various erroneous beliefs they may have.
"Early impressions are hard to eradicate from the mind. When once wool has been dyed purple, who can restore it to its previous whiteness?"
- "How can you seriously argue that you've discovered the Bible without using the Bible, when you are admitting that it was the Bible that told you to go look?[...] Their investigation was corrupted by bias from the very start. Instead of starting freshly, objectively and following the evidence to the best, most likely explanation, they kept the goal of the Biblical God in sight the entire time and adjusted their course accordingly. That is the difference between science and theology."
Psychologists have found that when people are presented with evidence that contradicts their view, people often react by rejecting the evidence and becoming more extreme in their views. This is known as the backfire effect.
A belief that is contradicted by evidence is often slightly modified with ad hoc reasoning and modification to prevent its disproof. These ad hoc reasonings were called auxiliary hypotheses by Karl Popper. Their problem is that they prevent an incorrect theory from being falsified. Carl Sagan point this out in his example of "The Dragon In My Garage".
Friedrich Nietzsche argued that confirmation bias was based on finding psychologically comforting explanations.
- "[We] identify as a cause something already familiar or experienced, something already inscribed in memory. Whatever is novel or strange or never before experienced is excluded. Thus one searches not just for any explanation to serve as a cause, but for a specific and preferred type of explanation: that which has most quickly and most frequently abolished the feeling of the strange, new, and hitherto unexperienced in the past — our most habitual explanations. Result: one type of causal explanation predominates more and more, is concentrated into a system and finally emerges as dominant — that is, as simply precluding other causes and explanations. The banker immediately thinks of 'business,' the Christian of 'sin,' and the girl of her love. "
Other explanations of confirmation bias including saving on mental effort and wishful thinking.