Vision Brain

 Today I learned, reading Incognito, that I have a blind spot. The book explains that our eyes have blindspots, located differently in each eye. I tried the experiment described in the book to prove this by making an L with each hand's thumb and forefinger, touching the thumbs together, holding them away from my face, closing one eye, focusing on the opposite index finger, and bringing my hands slowly toward my face. Nothing. Maybe it needs to be further out, so I made more of a W. Still nothing. Then I thought I may as well do the opposite even though I know it won't work. I angled both index fingers toward each other slightly and tried once again. If it had worked, I expected it to be very close to my face, but in fact the other finger vanished with my arms still mostly outstretched. 

 We never notice these blindspots because our brain fills in the details. In fact, our brain does most of the work in seeing. The author described the brain as being encased in a vault of darkness that is the skull. It makes up all the information about brightness, color, lines, and everything else. Speaking of lines, a blind man had his sight restored at age 43. He had been blind for 40 years. The doctors brought in his children so he could see them for the first time, but instead of joy, he expressed only confusion. In time he treasured every visage, but it took time. His brain needed months to learn how to see. One of the most confusing things was hallways. As a blind person, the lines of a hallway were parallel, but the brain sees them as converging to visualize depth. Another blind person who was very adept at finding her way around a room, memorizing every detail, was asked if she thought she could draw the room better than a sighted person. She said she had absolutely no concept of how to flatten a three dimensional space onto a piece of paper.

 The brain does wild things. It fills in details, but it also guesses, and sometimes gets things wrong. Ugh.