*Warning* this will get a little nerdy.
So I'm sitting in my truck waiting for the ferry and I'm killing time by playing solitaire on my phone (the regular 3-card-deal Klondike game) and when my *wins* tick over 300, I don't feel victorious... I actually feel a little pathetic 'cause I know before I got the new model of phone (not even a year ago), I had almost 500 wins on the old one.
So what does this have to do with compartmentalization?
We as human have an amazing ability to take in a glut of information and compartmentalize it in such a way that we ignore the majority of it.
We have to, otherwise we'd go crazy.
One tiny example is that the nerves in our skin will shut down/stop recognizing stimuli if it persists for a period of time. In proper english, this is why we don't go nuts from the constant feeling of our clothes touching our skin.
If you sweep your eyes over a garden of flowers, most people would probably be able to list a few of the colors they saw. Gardeners, on the other hand, would probably be able to list a number of the plants by name by that same quick glance.
If we feel the information is important, we remember it. If it isn't important, we ignore it.
So back to virtual card games...
If you don't know the game, you have seven stacks of facedown cards with the top one turned over, the first stack has one card, the last stack has seven. From the remaining deck, you flip over three cards at a time and, when possible, build onto the face up cards by placing them in descending order and alternating colors.
So, on a Jack of hearts, you can only put a ten of spades or a ten of clubs.
I have no logical reason to do this, but I always play the same way. In my brain, the suits go in order of importance... spades as most important, then hearts, clubs and finally diamonds. When I locate each ace, I place them in that order and, if accidentally they go out of order, I will actually waste a turn to put them in the correct order. When building onto the face up cards, I always try to pair hearts with spades and diamonds with clubs. This makes the game much harder to win because I'm cutting my options in half.
Like I said... there is no logical reason for this, but I still do it.
Now, I've been playing this game since I was like 5 or 6 years old. I've played it so long, I don't care if I win or lose and I can play on auto-pilot, even while following/engaging in a conversation or listening/taking in new information, like in a classroom setting (which used to drive my professors nuts when they would try to catch me out for not listening, and I'd snap right back with the correct answer).
My brain is so used to the game that it has compartmentalized certain aspects of it. It has decided that the specific order and pairing of cards is important, so I play this game without even realizing that I'm doing it. I actually have to actively be aware and change my automatic behavior to play differently.
Isn't this absurd? But I do it... and everyone does it.
And this is the reason why red herrings work.
Just like in the silly solitaire game, we are so used to taking in information by reading that we compartmentalize it. In every book, in every chapter, every scene, there is so much going on that we can't remember every little thing. So we organize the stimuli, our brain picks what it thinks is important and discards/ignores the rest. Murder mysteries in particular take advantage of this by describing a room, and hidden within that description is the murder weapon or some clue as to who the criminal is. The author tricks the reader's brain into seeing one thing as important so it will forget/ignore the rest of the information that is clearly there.
For some people, it can be fun to go back after the murder has been solved and re-read it to see where all the clues were laid out. For others, they get irritated if they can't figure out the solution on their own. I've heard a similar complaint from people who first pick up an Agatha Christie book. They say it was annoying, or that the author cheated because the clues were so ridiculously hidden/subtle that there's no way anyone could figure it out.
I've had people have this attitude to classic novels as well, stating they are too hard to read, but that's a topic for another day.
So, when you write, do you intentionally think about red herrings? Do you think about the reader and try to lead them along so they can discover *who done it*, or do you try to keep them in the dark until the twist/climax?