Understanding the physical act of seeing is almost easy compared to trying to understand the mental process – how we know what it is that we see.
When we look at something our eyes see outlines and shapes, and it is thanks to our prior knowledge that the outlines and shapes become known, whole objects. The Washington University School of Medicine has an online Neuroscience Tutorial, and the section on the Eye and retina includes this comment:
“Well, our entire visual system exists to see borders and contours. We see the world as a pattern of lines, even things as complex as a face. We judge colors and brightness by comparison, not by any absolute scale.”
So how, exactly, does our brain make sense out of what the eyes see? St. Luke’s Cataract & Laser Institute – Anatomy of the Eye breaks the eye down into its parts and describes them each in manageable chunks, including diagrams with some of the descriptions. Turns out the optic nerve is the information highway between the retina and the brain, sending electrical impulses from the retina that are then transformed into sense-making images in the brain.
An article on the UniSci site, To See, Brain Assembles Sketchy Images Eyes Feed It, sums this process up quite succinctly:
“The brain interprets this sparse information, probably merging it with images from memory, to create the world we know…”
In a John’s Hopkins study, reported in a Science Daily article, In the Mind’s Eye: How The Brain Makes A Whole Out Of Parts, one of the report’s authors states that
“Vision doesn’t happen in the eye, … It happens at multiple processing stages in the brain.”
No part of the brain is an island, each part has assistance from other parts. So it is with making sense out of what the eyes see. Previous memories, each stored in other areas of the brain, contribute to the understanding of the whole image.
And as with so many of our brain functions, seeing and understanding what we see both happen with such rapidity that under normal circumstances we don’t stop to think twice about it. As I have become reacquainted with the art of sketching, however, I now do think twice when looking and am better poised to appreciate what it is I am seeing.