Bias.

We all have it, and if you don't think you do, well lets face it, you are biased.
One of Murphy's laws states that, "Enough research will confirm your theory." OK. so I made that up. But it works for me.
You , or I, might give more weight to some evidence, or ignore other evidence, if we are embarrassed about it, or if we are stubborn, or for religious reasons, or superstitions, or traditions, or different views of the world or some other ideology. Or maybe you just don't like to admit making a mistake. I've met people like that! And so have you, we all have.
I might have a bias based on geography - I'm from the UK. "The UK can do, and never did do, any wrong."
We will point out any details that support our theory and ignore any that are contrary to it.
It's hard to be impartial. My Grandfather was on jury duty once, I'd hate to have had him on my jury, he said, "I could see as soon as they brought him in that he was guilty."
Tolstoy cleverly said, "The most difficult subjects can be explained to even to most slow witted man if he has not formed any idea on that already, but the simplest thing cannot be explained to the most intelligent man if he is firmly persuaded that he knows already without a shadow of a doubt what is laid before him."
I think we have a "gatekeeper" in our minds, this gatekeeper lets in beliefs and facts that we already agree with and shuts out those we don't.
An example - Hostile Media, you hear about it all the time, you expect the media to be hostile to your view, and it is, no matter what side you are on, if anything differs to your views, they are hostile.
A Republican will be biased toward a Conservative view, a Democrat will be be biased toward a Liberal view. And never the twain shall meet.
Or how about the placebo effect, if you have a smart doctor who acts as though the treatment he is giving you will work, it probably will. On the other hand if your doctor says "Try this, it might work, if it doesn't we'll try something else." Guess what, it likely won't work!
Bias, unfortunately we have to live with it, it is in all of us. Some more than others, it goes without saying that we should try to reduce those biases, and at least TRY to listen to the other persons point of view. Well that's my opinion anyway!
David, I love you anyway. XXX (But then I'm biased because you are lovable - because you read my blog)