Understanding the Unconscious Mind and Vision

One of the most important functions of your unconscious is the processing of data delivered by your eyes. That’s because, whether hunting or gathering, an animal that sees better eats better and avoids danger more effectively, and hence lives longer. As a result, evolution has arranged it so that about a third of your brain is devoted to processing vision: to interpreting color, detecting edges and motion, perceiving depth and distance, deciding the identity of objects, recognizing faces, and many other tasks.

Think of it—a third of your brain is busy doing all those things, yet you have little knowledge of or access to the processing. All that hard work proceeds outside your awareness, and then the result is offered to your conscious mind in a neat report, with the data digested and interpreted. As a result, you never have to bother figuring out what it means if these rods or those cones in your retinas absorb this or that number of photons, or to translate optic nerve data into a spatial distribution of light intensities and frequencies, and then into shapes, spatial positions, and meaning. Instead, while your unconscious mind is working feverishly to do all those things, you can relax in bed, recognizing, seemingly without effort, the lighting fixture on the ceiling-or the words in this book. Our visual system is not only one of the most important systems within our brain, it is also among the most studied areas in neuroscience. Understanding its workings can shed a lot of light on the way the two tiers of the human mind function together— and apart.

The main part of the human brain is divided into two cerebral hemi-spheres, which are almost mirror images of each other. Each hemisphere is divided into four lobes, a division originally motivated by the bones of the skull that overlie them. The lobes, in turn, are covered by a convoluted outer layer about the thickness of a formal dinner napkin. In humans, this outer covering, the neocortex, forms the largest part of the brain. It consists of six thinner layers, five of which contain nerve cells, and the projections that connect the layers to one another. There are also input and output connections from the neocortex to other parts of the brain and nervous system. Though thin, the neocortex is folded in a manner that allows almost three square feet of neural tissue —about the size of a large pizza-to be packed into your skull.” Different parts of the neocortex perform different functions. The occipital lobe is located at the very back of your head, and its cortex – the visual cortex-contains the main visual processing center of the brain.

A lot of what we know about the function of the occipital lobe comes from creatures in which that lobe has been damaged. You might look askance at someone who seeks to understand the function of the brakes on a car by driving one that doesn’t have any-but scientists selectively destroy parts of animals’ brains on the theory that one can learn what those parts do by studying animals in which they no longer do it. Since university ethics committees would frown on killing off parts of the brain in human subjects, researchers also comb hospitals seeking unfortunate people whom nature or an accident has rendered suitable for their study. This can be a tedious search because Mother Nature doesn’t care about the scientific usefulness of the injuries she inflicts.

Faces play a special role in human behavior. One looks at faces to quickly judge whether someone is happy or sad, content or dissatisfied, friendly or dangerous. And our honest reactions to events are reflected in facial expressions controlled in large part by our unconscious minds. Expressions are a key way we communicate and are difficult to suppress or fake, which is why great actors are hard to find. The importance of faces is reflected in the fact that, no matter how strongly men are drawn to the female form, or women to a man’s physique, we know of no part of the human brain dedicated to analyzing the nuances of bulging biceps or the curves of firm buttocks or breasts. But there is a discrete part of the brain that is used to analyze faces. It is called the fusiform face area.

The technique Koch’s group discovered exploits a visual phenomenon called binocular rivalry. Under the right circumstances, if one image is presented to your left eye while a different image is presented to your right eye, you won’t see both of them, somehow superimposed. Instead, you’ll perceive just one of the two images. Then, after a while, you’ll see the other image, and then the first again. The two images will alternate in that manner indefinitely. What Koch’s group found, however, was that if they present a changing image to one eye and a static one to the other, people will see only the changing image, and never the static one.” In other words, if your right eye were exposed to a film of two monkeys playing Ping-Pong and your left to a photo of a hundred-dollar bill, you’d be unaware of the static photo even though your left eye had recorded the data and transmitted it to your brain. The technique provides a powerful tool for creating, in a sense, artificial blindsight-a new way to study unconscious vision without destroying any part of the brain.

Source : Subliminal: How Your Unconscious Mind Rules Your Behavior by Leonard Mlodinow

Goodreads : https://www.goodreads.com/book/show/13058637-subliminal

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