For those of you who got it, you feel proud right? Then, there are the people who don't like to think about these things and the fact that I haven't posted the answer bothers them. Gestalt psychology indicates that people can solve general questions and if they don't get it, they feel left out. There are many different parts of this theory including the concept that we can recognize figures out of lines, we can see different images in one image, and we can see geometric shapes in different ways. Multistability is where we can go back and forth and experience two different perceptions of the image.
Some may see the bearded man's face or others might see a person sitting in an elaborate landscape. The mind is tricky, but you would be surprised at some of the things you will notice if you just take the time to look.
Oh, and i bet you are all wondering what the answer to the brain teaser is. The numbers are in alphabetical order.. :) [eight, five, four, nine...]
Picture Cite: http://brainden.com/optical-illusions.htm