Cognitive dissonance — the discomfort or mental stress that someone experiences when they have two contradictory thoughts, ideas, or beliefs — was an idea proposed by Leon Festinger back in 1957. He introduced the idea that when someone is presented with information that goes against their values and ideas, they either change their ideas to justify the stressful occurrence or actively avoiding social situations that are likely to expose them to the information that goes against their beliefs.
A study done in 1967 had undergrad students listen to a series of pre-recorded speeches that were staticky and hard to hear. The participants could push a button that would reduce the static for a few seconds for them to hear more clearly. Sometimes the speeches were about smoking — either linking it to cancer or denying the link — and other times it was attacking Christianity. The students who smoked pushed the button more when they were listening to the speech denying that there is a link between smoking and cancer; those who were nonsmokers pressed the button more when listening to the speech linking cancer to smoking. Similarly the churchgoers were content with ignoring the anti-Christian speeches while the less religious people gave the button significantly more presses.
In her 2015 book Respecting Truth: Willful Ignorance in the Internet Age, Lee McIntyre wrote “The real enemy of truth is not ignorance, doubt, or even disbelief. It is false knowledge.” People are going to be right and wrong, and many of those who are wrong believe things even thought there is a lack of evidence. How many people who believe climate change could actually explain how it works? Can the people who deny climate change explain why they choose to do so?
We constantly fail to realize that our beliefs are like expensive clothing, good food and travelling: it all affects our happiness. People try to fill their minds with information that makes us feel that what we believe is correct so that we don't feel discomfort and so we're not conscious that what be think is true might not be. Inherently when we know something isn't true that will harm our wellbeing, we pretend it is not so; we are like a lone fish swimming against the rest.
If you don't want to believe that your child is a bully at school or some other event is happening, we go to great lengths to explain why it is happening. We create an explanation that makes sense to us, and only us — everybody else who isn't emotionally invested is able to realize the truth. It's not to suggest that people aren't motivated to see the world accurately or that we never change our minds — we do. We simply sometimes have goals other than accuracy, like protecting our sense of self, which makes us resistant to changing our beliefs when we're presented with information telling us we should.