As anyone who has taken a camera and plunged into crowds on a busy street knows, the difference between a great photograph and one for the outtake bin can be a matter of mere slivers of a second. The decision making process happens faster than reason can account for. In fast moving situations, the pictures have to made so quickly that they are only understandable in retrospect.
The number of computational decisions that have to be made in the creation of any good photograph is staggering. If you place the picture making process in a fast moving and changing environment, it is even more impressive that it happens at all. Research indicates that the processes that handle these computations in the brain occur in the cerebellum. These guys are figuring out how it works.