Gestalt occurs when we only have partial information and we tend to fill in missing info. For instance, many optical illusions illustrate the concept of GESTALT. Stereotypes are also a type of GESTALT which are normal for us to use, but can become negative when we rely only on the generalization instead of facts.
Is it a rabbit or a duck? How many legs?
Where does it all connect? How many squares do you see?
MC Escher was also well known for his mathematical Tessellations which played with people's perception...
Where do the pillars settle? Tessellations
Black geese or white geese? M.C. Escher Self-Porttrait