Human brains have what is sometimes loosely called the "limbic system" - it is a group of structures that are tied to memory and emotion. It is, among other things, responsible for engaging in fast judgements, to protect you from harm - the system that, based on just a little information, says, "Oh, crap! Jaguar!" and the like.
This system tends to return results faster than your conscious, logical processes can. And this is really good for you if there's a jaguar around. Having established an emotional context, you can then very quickly sort through the results of the rational mind, to find one that fits. It is highly efficient that way.
When you do that with written text, that has low risk to you and little or no time pressure, though, it tends to fail - your brain will sometimes establish your emotional response to the work seconds or even minutes before you actually finish reading the work - and material that is not consistent with the emotional response tends to get ignored, even if it contradicts the reason for the emotional reaction.
