Rules of Perceptual Organization (closure, continuity, similarity)

Closure

Our brains fill in empty gaps in order to complete a whole object. This usually helps us to construct reality, but sometimes it only confuses us.

These four objects, although unrelated, looks like they form the corners of a rectangle.

Continuity

Our brains take discontinued patterns and make us perceive them as smooth and continuous.

Our brains see these lines as a squiggly line and two or three straight lines when in reality it's two half circles, a quarter circle, and three straight lines. 

Similarity

Our brains group objects with similar features together.

Our brains group together the similar objects so we perceive the triangles as a pattern on a five sided die and the rectangles as a diamond shape.