Perception

As we develop from infancy our brains digest and interpret impulses from our optic nerves. Experience (memory) creates our visual reality. Sometimes we get tricked, perceiving something one way when further examination reveals it to be quite different.

Three dimensional objects presented in two dimensions can be tricky to decipher. The image is of a mask, about three inches (7.6 cm) deep. The mask is concave. That is, the surrounding surface (brownish color) is closest to the observer. The tip of the nose is furthest away.