Contemporary Cognitive Neuroscience :Brain and Mind-Feeling and Perception
焦傳金教授 Professor Dr. Chiao.
3 Dimensions vision
The Professor told us that if put your two eyes n different spot of a picture which was designed in the special way. If we relax our eyes and do not make them focus on the specific spot, we could see the hidden shape in the picture. That is, the more efforts you want to focus on the picture, the little chance you can see the hidden shape.
I have once read a book written by a Japanese author, Sadaharu Fujino, who use the 3 Dimensions way to relax our eyes on order to heal the nearsighted. While the reader should see the hidden shape of the picture to level up to the next page.