Cognitive fluency is how well your system is zeroing in on the relevant information.
“When you increase the ease at which people can process information, regardless of what that information is, they come to believe it is more real, they have more confidence in it etc. That can be something very simple. It can be as simple as changing the font contrast between the letters and the page. So, consider two individuals Tom and Susan. Tom is reading words in which the color contrast between the letters and the page isn’t as good as the color contrast that Susan’s reading. They’re reading exactly the same thing. They can both clearly read it. It’s just the font difference makes it easier for Susan than for Tom. As a result Susan will judge the information as more trustworthy.”
“When I do something that increases your cognitive fluency, your brain generates an enhanced sense that you’re actually in touch with things. That turns out to be a good policy your brain is using. It’s a very good idea for your brain to try and use the fluency of its own processing as a measure of how much it’s in touch with reality.”
This was demonstrated in research by Reber and Greifeneder.