Thursday, July 23, 2009

Optical Illusions Reveal That What We See Isn't Necessarily What's There

It's remarkable what we can do visually. We can see a face or any object, and nearly instantly recognize it. We can detect motion and automatically track the speed and direction through 3D space. Etc. Etc. You have eyes. You know what we're capable of. But we like to imagine that our eyes are like cameras. Perfect reproducers of the unalterable world as it is. It's comforting to think that what we see is always what is there to be seen. But we know that isn't true. Our brains accomplish high-level visual tasks by taking the incoming data from our eyes and performing all sorts of filtering and decoding tasks, applying shortcuts and pre-constructed models of reality. Transparently. The beauty of our ocular system is that we are nearly completely unaware that our brains are changing what our eyes see, and only showing us what we need. All this occurs in the brain, through filtering and wetware calculations, without our awareness catching wind of the process.

So I love optical illusions that manage to shed light on these and trick our brains into revealing the filtering and the manipulating it's doing to our visual world. It's like getting a peek at the man behind the curtain. By short-circuiting what is normally a transparent, automatic process we get a sense of just how powerful our brains are. Here's a few of my favorites from a site I found recently. There are many more.

An example of motion-induced blindness.
The Stereokinetic Effect
This one really caught me off guard. Since the last few illusions I'd looked at were animated, I just assumed this one was too. But it's an entirely still image. Look closely...

I've always loved this effect.

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