“Reality … what a concept!” This title of a CD by the late Robin Williams suggests that what we think of as reality is our own conceptualization, and I believe that the brain assembles the only reality we are able to know. Every message we receive through our ears, eyes, nose, tongue, and skin is elaborately processed before we become aware of it. There is no way to experience life as raw data. Our brains feed us French toast rather than kernels of wheat topped with unshelled eggs. In that sense the direct realist’s claim that nothing stands between us and the objects we perceive is rather misleading.
Perceptions are processed in ways that help us cope. For example, visual information is cleaned up and enhanced after it arrives in the brain. Suppose we are looking at an object that is equally bright all over its surface, according to exact measurements of brightness levels. To us its brightness will not seem uniform; it will seem brighter at the edges and corners than in the middle. By artificially brightening edges and corners the brain exaggerates boundaries, so that it’s easier to tell one thing from another. How convenient to see a universe of specific objects instead of a swirl of bewildering stimuli.
Changes are also exaggerated, making it easier to notice the movements of an animal. And when we watch a moving object, we experience it as being slightly ahead of its actual location. This helps a baseball player hit a fastball that’s ripping along at nearly 100 mph – and helps pitchers fool batters by throwing them a curve. Cavanagh reports that “when targets are moving, they are seen ahead of their actual retinal location because they are seen at their predicted next location” (“Perceived Location: A New Measure of Attention,” Conference Handbook, Association for the Scientific Study of Consciousness, July, 2013, p. 15).
There are blood vessels in the eye, right in front of the retina, and it would be confusing to peek out at the world through a grillwork of capillaries. So how does the brain solve this problem? Very simply. Anything that stays perfectly still in relation to the eyeball is invisible. Whenever the eyeball moves, the blood vessels move with it, so the blood vessels aren’t seen except under unusual conditions.
As you look at an object, a river of information flows up the 1.2 million fibers of your optic nerve into your brain. Once it arrives there, an early stage of processing establishes edges. One neural system graphs the horizontal lines and another attends to straight-up-and-down vertical lines. Others monitor an object’s shape, color, location, or name.
Sometimes people who have had a small stroke will lose one of these subsystems, but the others will remain intact. For instance, they may be able to name an object they are looking at and accurately describe it – but they have no idea where the object is located in relation to other objects! Their visual experience has changed in a way that is virtually impossible for normal people to imagine. They’ve lost their inner map of object location.
In a film called The Truman Show, the main character starts to suspect that what he thinks is real is just a made-up story. Eventually he discovers that the world he had known since birth was actually an enormous stage set. And we are all the stars of our own Truman Show. The brain manufactures our world and fabricates the way we feel about it. Presumably a lot of this brain-made story is reasonably accurate, but some of it is pure fantasy.
I like to picture my brain as a huge Tinkertoy sculpture, with billions of interconnected spools and dowels. Activate the connections of these units in one way and you feel like dancing. Switch around their activation patterns and you sink into existential angst. It seems as if “reality” has changed, but it’s all just patterns in our heads. If you can change the pattern, you can change yourself.
Roger Christan Schriner