Confirmation bias is dangerous in reasoning because it makes a person:

1. A bias distorts which evidence reaches the conclusion. 2. The confirmation bias is the tendency to focus on information that confirms your existing beliefs. 3. Evidence against the belief is available but attended to less. 4. The result is that a belief appears well supported no matter what the full evidence says. 5. Changing beliefs too readily is the opposite failing. _Source: OpenStax Psychology 2e (CC BY 4.0), Ch 7 'Thinking and Intelligence', sections 7.1-7.5_