Difference between conceptual & perceptual

I don't usually like seeing pictures of myself, but I caught a yearbook staffer trying to shoot me during 7th Grade Art and it occurred to me that I may as well be using this blog as part of my teaching portfolio that the State requires. Also a chance to share some stuff with elementary teachers for their professional development and to reinforce stuff that high school drawing students are learning.

To introduce junior high students to the element of design, line and to drawing, we talked about how to accurately draw what you see in real life, you have to overcome the prior knowledge you already have of the subject matter. In other words, to avoid making mistakes, you have to avoid letting your fast working, logical brain from superimposing concepts about things and using over-simplified "clip art."
For example. Our brains "know" that a stool has a circle for a top, and four legs that are all the same length and all on a flat level. Ah, but knowing is not seeing. What we see, is an elliptical top that is way to narrow to ever sit on, and each of the legs is a different length and even a different width. Kids often make mistakes in drawing because they "know" too much about what they are looking at, resulting in distorted perspectives and overly simplified images. Ironically, Cubists like Picasso drew that way on purpose, because they were visually analyzing and abstracting the basic concepts and geometric shapes of things from multiple perspectives simultaneously.

Is this getting a little deep? Maybe the next picture will make more sense.

We "know" that adult humans have 32 teeth. But if you draw a smile with exactly 32 teeth in it, it's going to look ridiculous, because even Jack Nicholson as the Joker in the Batman movie doesn't have a broad enough jaw to show all 32 teeth! Gums and lips and tongue and the natural curve (the "arch" as dentists call it) all conspire to hide most of them. The best way to draw teeth is not to. by focusing on the negative-space around the teeth and the shared edge between the teeth and the darkness of the inside of your mouth, you're much more likely to record accurate perceptions where the size and placement relationships are more correct.