optical+illusions

=Optical Illusions=

toc Read here about optical illusions and the role they play in raising awareness about the limitations of our sensory perceptions.

=Overview= Optical illusions are a simple and powerful educational strategy to raise awareness about the limitations of our sensory perceptions. This is a critical concept in scale, as we must keep in mind that "what you see is **not** what you get" in other scales.



=Moon Size Illusion= The moon size illusion carries an important message about how real our perception can feel--and how wrong it is at the same time.

Narrative of the Moon Size Illusion
For example, why does the moon look so much larger when it’s at the horizon than when it’s overhead, at the zenith? This is a question about conscious experience — about how the world looks to us — not about behavior and brains. And there is a clear and convincing evolutionary explanation. The visual system wasn’t designed to deal with objects that are thousands of miles away. It was designed to accurately judge the size of close, evolutionarily relevant objects like apples. As an apple moves closer or farther away, it will project a larger or smaller image on my retina. But I don’t see the apple expand and contract. I see an apple with a concrete, stable size. This is because my brain evolved to combine information about the size of the retinal image with information about distance to create a single, constant visual experience. The retinal image of the moon is always about the same size. But the horizon looks farther away than the zenith, perhaps because we see that other objects are in front of the horizon while the zenith is unoccluded. The brain determines that the horizon moon must therefore actually be larger than the zenith moon. And, voilà, the rising moon looks much bigger. So we actually have a good and interesting naturalistic explanation for this particular feature of our conscious experience and many others like it. But it seems that we can’t explain the most important thing: Why does the moon look like anything at all? What explains that ineffable je ne sais quoi, that irreducible magic of experience? That big, beautiful moon doesn’t just feel like the outcome of a cool calculation. And it isn’t looming up at just anyone, but at me, the equally ineffable and irreducible self. Humphrey’s clever and original idea is to treat these intuitions about consciousness — this sense of ineffability, specialness, irreducibility and point of view — as simply more features of experience to be explained, the way we explain the apparent size of the moon. Maybe we experience consciousness as special because it really is special. But maybe those intuitions are as illusory as the shrinking and growing moon. We know how the details of our visual experience, like the experience of size constancy of objects, are related to our need to survive. But what is the evolutionary function of the experience of the ineffable and irreducible? Humphrey points to a feature of consciousness that has been surprisingly neglected. “The bottom line about how consciousness changes the human outlook — as deep an existential truth as anyone could ask for — is this: We do not want to be zombies,” he writes. “We like ‘being present,’ we like having it ‘be like something to be me.’ ” Humphrey ingeniously works out the many consequences of this apparently simple fact. He points out, for example, that we humans will work as hard to get a newer or more vivid or more intense experience as we will to get a meal or a mate. Almost as soon as we could use tools to make hearths and spears, we also used them to construct consciousness-­expanding art installations in painted caves like Altamira. We fear death so profoundly not because it means the end of our body but because it means the end of our consciousness — better to be a spirit in heaven than a zombie on earth.

=Links and Citations=

See also Artworks About Scale

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