Top-Down Visual Processing

I thought this bus advertisement for the Copenhagen Zoo was particularly "gripping". The snake itself startling, but what really makes this paint job excellent is how the bus actually appears to be crushed. Though the edges around the snake are black, and the colors around the "crushed" areas are distorted, the effect is quite convincing. This comes from our Top-down visual processing of the image. We expect a black area in this case to be a shadow (from an absence of material), and shades of color indicate to us the material has depth, and is deformed. This effect is especially strong when we only see it in a two-dimensional image.

From Bates Y&R, Copenhagen