Yesterday I was talking a lot about neural networks and the brain. Later that night, I came across an article about a funny optical illusion.
When you look at this picture, it looks like two wavy shapes, one inside the other. Would it surprise you to learn that they are actually both circles? Check it out:
If you want, you can take the original image and put it in Paint and draw your own circles if you don’t believe me.
The interesting thing is that even though you now know they are circles, you still really don’t see circles when you look at the original image. This is what makes optical illusions so awesome – they reveal something about how the brain really works. Here is another example:
When you look at this image, which appears to be a cube sitting at a 45° angle on the ground, you see that one face of the cube is a dark gray while the other is light gray. Now look at this:
It is the same image, only I have covered the middle region between the faces with a rectangle that has the same shade as the top part of the cube, and now you can clearly see that the two shades of gray are the same! Feel free to copy this one to paint and try it out for yourself. And just like with the circles, even though you know the shades are the same, you just don’t see it that way.
So what the heck is going on? How is our brain being fooled into seeing things not as they actually are? It turns out that the answer lies in the world of psychology. There are a number of experiments that you can do visually that show that what the brain actually does is to take the information that it gets from your eyes and then processes it before you actually “see” it.
One interesting example of this phenomenon that we see almost every day is when we look at a TV, computer monitor, or even a movie screen.
This is an image that depicts different ways that computer monitors update what is on the screen. As you can see from the image above, the monitor is actually flashing light at us continually. If we speed up the rate the image is refreshed, the brain will eventually fill in the dark time periods with the image that it previously saw so that we become unaware that there was a gap between the refreshes. Old movie projectors work the same way – what you are actually seeing is a series of pictures (usually 24 per second) being flashed on the screen, but your brain connects the images so that they appear to be continuous.
Another great example is if you stare at this image of a spiral for a few moments (10 – 15 seconds) and then look at a different part of the screen (like the words above it):
Did it look like the words above were expanding? You know that they were not, but your brain made it look that way for a few seconds.
Your brain uses little tricks like this to compensate for motion in what it is seeing. The reason it does this is to make those images appear more stable than they really are. If you stare at a flowing waterfall for a few moments and then look elsewhere, you will see things rising up.
Most likely, this is a survival mechanism, because as you are scanning around you, looking for predators, it would be a lot harder to spot them if you couldn’t really see them in the blur while your head was turning. So your brain compensates and this allows you to see things more clearly while your head is moving, but when your head stops moving, it takes a moment for your brain to stop compensating, and so you might see effects like the one above.
This just goes to show that your brain processes visual information much in the same way it processes other signals from your other senses. When you hear a sound you have heard before, you can usually identify the type of sound almost immediately without even thinking about it – again, a survival mechanism because sometimes you don’t really have the time to stop and think about whether the sound is a predator or not. How some of this all works is still a mystery, but as I talked about in my last post, it is likely due to connections in the brain that happen so that certain neurons fire given certain inputs so that we can almost immediately perceive threats and react quickly. In a way, we are smart beings because we had to be to survive.
It almost makes you wonder if Idiocracy is becoming true because we simply don’t have to use our brains for survival as much any more. Who really knows.