Mona Lisa looks just fine in the first picture, but there is something terribly wrong with her in the second. She is frowning and her eyes are looking down or they are upside down. Now, turn your head upside down... c'mon it's not that hard! And look at the second picture. The face will pretty much look fine to you. Both of the pictures will look very similar if you do this. Press SPACE to rotate the picture!
Here is the same picture, it has been rotated but… … her expressions are still the opposite!
Study the dots above and see if you can spot the dog. Hidden in the dots is a picture of a dalmation, sniffing the pavement. This shows how even though the lines aren't connected, our minds will recognize familiar objects more easily than random shapes.
A personal favourite… Do you see: A) Rabbit B) Duck C) Both?! IF YOU LOOK CLOSELY, YOU CAN SEE BOTH!