Wednesday, January 30, 2013

Brain Rule #10: Vision

My summaries of the book Brain Rules continue...
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Chapter 10: Vision
Rule #10: Vision trumps all other senses.

"We see with our brains" (224). In the previous chapter, Medina has talked about the model that sees our senses sending information to brain centers and then on to higher regions of perception. He suggests that the process is much messier, involving interaction with other senses early in the process and a "top down" element of interpretation that results in differing interpretations of the same experiences.

Our vision is a great illustration of this messiness.  For one thing, processing of vision seems to start not at our vision center at the back of the brain but with the retina itself at the back of our eyes. Our retina takes light patterns and makes partial "movies" called "tracks" (225). One of these tracks involves outlines and edges, another processes motion, another has to do with shadows.

Perhaps as many as a dozen little amateur "filmmakers" send these movies simultaneously to the back of the brain for integration and further interpretation. If one of these tracks is defective, a person may not be able to discern motion or some other central element of vision. The tracks go to the thalamus and then emerge in greater combination.

Eventually the information flows in two streams.  The ventral stream recognizes what an object is along with its color. The dorsal stream recognizes location and whether something is moving. The "association regions" mentioned in the previous chapter work to integrate these electrical signals.

Far from the brain seeing exactly what is there, it makes some guesses and fills in some blanks.  It fills in the blind spot in our sight, for example.  The brain takes the differing images coming from each eye and combines them together so that you only see one outside picture.  People with Charles Bonnet Syndrome actually hallucinate people and things that they know are not there.  Their brain simply fills in the details wrongly.  The brain devotes about half of its resources to the act of seeing.

A lot of what we see is actually our brain guessing what is out there based on prior experience.  Many will be acquainted with "phantom-limb" experiences.  This is where the brain continues to feel a limb that is actually no longer there. Some individuals experience pain in this limb that no longer exists. One way to alleviate that pain is to put a mirror up against a remaining limb so that it looks like there is another limb beside it.  Sometimes, the vision convinces the subconscious enough that the pain will diminish.

An average person might remember 10% of a lecture.  If pictures are combined appropriately with the lecture, that figure goes up to 65%. The dominance of vision over all the other senses begins in infancy.  It is reflected in our very DNA, where scientists would say vision has taken over massive amounts of genetic material devoted to smell previously, about 60%.

Medina ends the chapter with some ideas. For example, he suggests that we throw out our old PowerPoint presentations, the ones with way too much text on them and no pictures. "Less text, more pictures" (238) brought USA Today criticism in 1982 when it started, but it is the most read newspaper in the United States today. Pictures grab attention because the brain is wired to pay attention to color, orientation, size, and motion.  It helped us survive in the Serengeti in an earlier phase of the species.

Software allows people today to create simple but effective computer animations. Medina tells how his career choice was inspired by an early animated short in 1959 called Donald in Mathmagic Land.  "We learn and remember best through pictures, not through written or spoken words" (240).

1 comment:

Ken Schenck said...

I might add that these facts show how ineffective a sermon consisting of just words is. It is as ineffective as a lecture, 10% retention on average.

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