Although finding contradictory evidence is unlikely to kill us, it may still be a threat to our pride (or even our employment!). This, we tell ourselves, is the correct way to run a school, to manage a class, to teach this subject, to interact with students. How do we know? We just do. We tend to have a lot invested in our beliefs – time, effort, credibility – and if we find evidence that we might be wrong, we run the risk of looking foolish. So, it makes sense not to check.
