Building Reality

In the book Vision and Art: The Biology of Seeing by neurobiologist Margaret S. Livingstone, we learn the acuity of the human eye is surprisingly low. The eye's full resolution is only available in the very center of our gaze in an area slightly larger than a thumbnail and it drops off rapidly from there. The image below is an approximation of how much of a printed page is sharply in focus for us when reading.



Let me emphasize, this image is a rough approximation. Obviously, you can reproduce this "experiment" for real by taking a printed page and choosing a word in the text to look at. Keep your gaze on that one word and notice how much of the surrounding text you can see in focus. Admittedly, it's kind of tricky to do this, because the natural inclination is to shift your gaze to adjoining words as you try to see them.

Studies made of how we read show our eyes constantly shift along the line we are reading, jumping ahead a word or two and backtracking a word or two. Thus, we get the illusion that the whole page is in focus rather than just the word or two in the center of our gaze. When we are seeing our environment, the same principle is at work. Our gaze constantly shifts on our surroundings. From this constantly shifting gaze, our brain builds the illusion of the in-focus world we "think" we see, and it does all this in real time!

I would posit that visual perception plays a large part in the widely held "common sense" theory of perception, "naive realism". But, the more you learn about visual perception, the more you realize how much the picture of reality in our heads is constructed in our minds rather than being a one-to-one reflection of the reality that is "out there".