A simple question: is wine healthy? Yet your answer may not be so simple. It will not be based purely on facts but also on your personal point of view. If you love sipping wine, your brain will start to look for arguments to prove that wine is actually good for your health. You will even mention antioxidants, the “good” ingredients of red wine, which increase the level of “good” cholesterol in the blood. So you will conclude that wine can definitely prevent you from having a heart attack.
On the other hand, if you believe that wine is unhealthy, you’ll find arguments which support that theory, too. There are plenty of scientific papers arguing that there is nothing like a “safe” amount of alcohol or that this amount depends on an individual’s physical condition. No matter whether it’s true or not, you will select only those arguments that prove you’re right.
Our brain messes up the truth
According to what cognitive scientist, Hugo Mercier and Dan Sperber, found in their research, our reasoning has evolved in such a way that it does not help us seek for the truth but rather fulfill our social needs.
“What reason does, rather, is help us justify our beliefs and actions to others, convince them through argumentation, and evaluate the justifications and arguments that others address to us.”
Their theory of reasoning described in The Enigma of Reason  states that we tend to look for information that supports our current beliefs. Thus, we treat the contradicting arguments as invalid and we simply reject them. It lets us fall into confirmation bias.
Confirmation bias makes us look for arguments that support only our current point of view. That effect is especially strong in the case of emotionally charged topics and our deeply entrenched beliefs, such as politics, vaccines, gun laws and policies. These topics are emotionally charged and they divide people into two categories: opponents and proponents. That’s why we can easily fall into confirmation bias while discussing those issues.We choose arguments that support our beliefs
We choose arguments that support our beliefs
One study  showed that people who had great math skills were only good at solving a math problem if the solution to it conformed to their political beliefs. Liberals were only good at solving problems when the result showed that gun control would decrease the crime rate. Conservatives managed to find a solution if the result showed that gun control would increase the crime rate.
What it means is that we use reasoning capacity selectively. We do our best only when we are able to support our current beliefs. That’s why many topics, especially politics, are highly inflammatory.
IQ score doesn’t make a difference
Confirmation bias also affects well educated people and those with high IQ. People, who reject scientific evidence about issues like vaccines, the shape of the earth or the evolution, are actually affected similarly by it. They can even read the same research studies and articles.
“What the heck this guy is talking about? I bet he didn’t go to school!”
You may sometimes consider them to be unintelligent or simply stupid. But is it actually caused by the lack of knowledge? Not necessarily. They just look for arguments opposite to yours. Their brains are selectively choosing arguments.
In another study  researchers analyzed how an individual’s IQ impacted their reasoning. The results were quite interesting. The higher someone’s IQ was, the better they were… but not at finding the truth. They were much better at finding the best arguments to support their opinions. So intelligence can help you find better arguments for yourself but not necessarily find the truth.
This fact is more relevant
Even if we have a series of different facts we credit those which support our opinions with more relevance. When some facts are against our point of view it doesn’t mean we instantly deny them but we do consider them less relevant.
Let’s say you’re discussing nuclear-power safety. One argument is that nuclear energy may be considered “green” because greenhouse gases are not released during the operation of the plant. But another argument is that there can be severe safety issues in case of theft or attack. If you’re a proponent of nuclear energy, you’ll find the second argument less relevant.
People tend to choose facts selectively, meaning only those facts that support their beliefs. It doesn’t necessarily mean that they are stupid. It has nothing to do with their IQ level and intelligence. That’s why focusing only on facts isn’t enough to change somebody else’s mind, especially if that someone has already prepared their own facts.
If you want to persuade someone of your convictions, you need to focus on the root of the problem and understand why that person doesn’t want to change his opinion. It will probably be connected with his political or social affiliations, since our brains use reasoning not to explicitly find the truth, but rather to satisfy our social needs.
 Hugo Mercier, Dan Sperber. Harvard University Press. 2017. The Enigma of Reason.
 Kahan, Dan M. and Peters, Ellen and Dawson, Erica and Slovic, Paul. Yale Law School, Public Law Working Paper No. 307. 2013. Motivated Numeracy and Enlightened Self-Government.
 Perkins, D. N. Farady, Michael Bushey, Barbara. Informal reasoning and education (pp. 83-105). 1991. Everyday reasoning and the roots of intelligence.