If you want your reader to retain what you tell them, then this is the page you need to read.
Seven is the Magic Number!
Have you ever stopped to think about why a phone number has seven digits in it? That's because seven is the maximum number of things you can remember at the same time.
I hear you telling me I've gone off the deep end, but it's true.
If you give an average person a list of ten items and let them read it for one minute and then take it away, how many of those items can they recite back to you assuming they didn't know it was a test? The answer is seven.
Humor me for a minute and keep reading.
Think of this as seven hooks on the wall of your mind. Think of the things you are hanging on the hooks as coats. You can hang seven coats on the hooks and see them all at the same time.
If you need to hang up another coat, you'll have to put it on top of one of the other coats hanging there, just like you would do it on a coat tree standing in your hallway when you have more than seven guests over.
Making a Point
Less than seven is okay, but if a mind has hooks left over it tends to wander away from the occupied hooks. Be sure you have seven items that you cover in order to keep your reader's interest level and, at the same time, not overwhelm them.
Have I used the Seven Hooks?
You tell me. Have you retained what I've said so far? Some sections have seven and some don't. The sections where you are retaining the information the best are the ones that had seven items.
No, you can't go back and count the headers to see if there are seven things in each section. I'm a lot more clever than that with my writing, or at least I sure hope I am!
Retention is also Examples
The better your readers can relate to the examples you use, the longer they will retain what you tell them. If you can build on an example previously used, that reinforces the example in the minds of the reader.
I have to admit that I've done a poor job of giving you examples, the carb thing just didn't pan out the way I had hoped it would. But maybe it served to show you something far more important. It was a lesson in how NOT to do something, which is just as valuable as a lesson in how to do it right.