I've decided to compile an ongoing list of the best illusions on the internet. Be sure to let me know if you come across any awesome illusions, so I can add them to the list.
I divided them into two easy to find sections: Optical Illusions and Auditory Illusions. Seems like those are the only two possible illusions, but the internet is a crazy place, so you never know.
1) Black and White Castle Illusion
We'll start things off with a fun little video displaying the optical illusion known as "Chromatic Adaptation." The image of a black and white castle will be magically filled with natural colors, right before your eyes. Amazing!
2) The Hollow Face Illusion
The Hollow Face Illusion, or Hollow Mask Illusion, is where the inside of a mask looks like a normal face. Or to put it into scientific mumbo-jumbo, "the perception of a concave mask of a face appears as a normal convex face." Apparently we're so used to seeing normal faces that we just can't make sense of it any other way.
This first example is my favorite video of the Hollow Face Illusion. This guy does a good job of explaining the effect while it's happening. Plus he has a British accent, so you feel smarter after listening to him:
Hollow Face Optical Illusion - Charlie Chaplin
Another cool example of this illusion is the Gardner Dragon. As a bit of history, this paper dragon was created by Jerry Andrus as a part of Gathering for Gardner.
Gathering for Gardner Dragon
As an interesting side note, if you are schizophrenic, you won't be fooled by the hollow face illusion. See this article for details: Hollow mask illusion fails to fool schizophrenia patients
If you want to see plenty more examples of the hollow face illusion, just click here.
3) The Checker Shadow Illusion
The Checker Shadow Illusion is a popular illusion created by Professor Edward Adelson at MIT. Believe it or not, the squares labeled "A" and "B" are actually the same shade of gray. Below are a couple of cool videos that demonstrate the effect.
Checker Shadow Illusion Revealed Using Photoshoop
Checker Shadow Illusion Revealed Using Life-Sized Model
1) Shepard's Ascending Tone
We'll start of the sound illusions with a fun little video that shows an example of Shepard's Ascending Tone. Listen to the video as the tones appear to "creep up" the scale. Wild and crazy stuff!
2) Falling Bells Illusion
For this illusion, you need to be wearing headphones. I guess you don't have to wear headphones, but it's better if you do. The bells will sound like they're falling all around you. And that the tones are getting lower and lower, but really they aren't. It's a mindblow for sure.
3) The McGurk Effect
Anything I could possibly explain about the McGurk Effect can be summed up in the following video. It's quite the informational treasure trove.
I'm also throwing in the following video of the effect, because it shows the "ga ga ga" sound. First, listen to this video with your eyes closed. I think most people hear the "ba ba ba" sound. Then play it again and watch it. You should hear "ga ga ga."
4) The Virtual Barber Shop
This next illusion is one of my absolute favorites. You definitely need to put on headphones for this effect. It is a demonstration of stereo sound, and you'll be able to hear sounds in space as if they are actually moving around you. The best way to explain it is to say, it is awesome!
5) Phantom Words
This next auditory illusion is actually kinda creepy. Apparently all that is playing is meaningless noise. However as you listen to that noise, your brain will start to pick out words and phrases to make sense of everything. The weird thing is that these words will start changing. I hear different words all the time. It's a weird feeling.
Bonus "Brain Game" Footage:
Thanks to Brian for pointing these out. Nat Geo has a program called Brain Games, and they pretty much cover everything in this post. So, if you still haven't gotten your fill of illusions, I'll add episodes as I find them. Enjoy!
Brain Games - Watch This
Brain Games - Pay Attention
Brain Games - Remember This