09
Oct
11

Amazing Book on Perception

I just finished “Sight Unseen” by Melvyn Goodale and David Milner, two researchers of percetion.

This book is just really good. It’s short and accessible but awesome in the way it will change your thinking.

The main idea is that we have two perceptual systems, one for action and one for representation. The deepness in which these themes are pursued is truly impressive.

Dee Fletcher, the main research subject of the book, lost the ability to see objects as objects. Her visual experience is hazy and objects seem to “run together,” but she can see color and texture. HOWEVER, she is still able to act like normal human beings. She can mail a letter in a small slot, grasp objects of a variety of shapes and so on. The evidence amassed over the course of the book is impressive. The representational system is closely tied to consciousness and is not much use for action. If we see an object, we can pick it up easily, quickly, and with the right amount of visua-motor adjustment. If we wait a few seconds while our eyes our closed and SIMULATE picking up the same object, we’re slower and less adroit with our motions, the hypothesis being that information for our motor system clears out after a short period of time, leaving us with our perceptual system, which is not built for action.

The idea is strengthened by patients who have damaged visual systems for action. These people can see everything crystal clear, but have trouble and uncertainty ACTING. If such people wait a few seconds to engage with an object, their performance improves, because rather than engaging their ordinarily superior (but now broken) motor-vision system, they engage their work (but second-rate) representational-vision system.

This is used to explain a wealth of ordinary and fascinating data. First, why do young kids draw the same pictures of houses and cars, but master artists can introduce perspective and the appearance of reality? The reason is that our eyes work “behind our backs” to create object recognition over time. A black shirt in sunlight reflects more light than a white shirt in a dim room, but the former still looks black and the latter still looks white. That’s our brain helping us and compensating for what we “see” (see is in quotes because I’m using that word to refer crudely to just the light that hits our retina. Real perception is much, much more than just light hitting the retina). So, young children draw things as the OBJECT is. We recognize a door from all sorts of positions, even though a door’s shape on our retina can be trapezoidal, parallelogram, or square depending on the perspective. But throughout it all we recognize a door, and that’s why kids draw the door as the object the brain cues to us — the rectangular straight on object. Master artists have in a sense mastered the ILLUSION and clues our brain uses to help us see perspective.

Also, why is it hard to mime actions. Well, because of what I said before. We’re quite bad at mimicking the FLUIDITY of action that is guided by our motor system. Painters have to learn to recreate what our REPRESENTATIONAL visiionsystem does for us, but mimes must learn to duplicate actions normally controlled by our ACTIONAL visual system. That’s why miming is really hard.

Something that really blew me away, is that TV would be impossible without our representational visual system. All the lower mammals have an actional visual system, but only we have a representational system which works mainly by relative distances and sizes. Thus, everything on a TV looks right, because its compared to everything else on the TV. Godzilla looks big (even though he’s small) and 3-d (even though he is on a 2-d screen).

The MOST interesting thing though was that our representational system can be fooled by illusions but our actional visual system CANNOT. When looking at a line illusion (with the arrows) we can’t help but SEE the lines as different lengths, but if we try and reach out to grab the lines, our fingers will stretch the right distance. They won’t be fooled by the illusion. What this means is that acting in the world reveals the truth of the world in a special way. ONLY through action can we work around some illusions. The world is revealed to us in a special way when we TAKE action. Is there some relationship to the wall street protests, i.e. when we ACT on our political beliefs rather than just think about them, the world maybe revealed to us in a special way. I’m fascinated by that thought.

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