A baby moves her finger across a spilled milk and looks with an interest at a mark that her gesture leaves behind. A toddler holding a felt penwith a firm grip hits a sheet of paper covering it with a rain of dots. A preschooler attentively adds lines to an oval explaining that his dog has just run away. A third-grader completes a collage made of tiny pieces of orange paper to celebrate Halloween. Her companion adds another Little Kitty drawing to the margins of the notebook. A teenager, with his hands and face splashed with mud adds finishing touches to a vase swirling on a potters wheel while his classmate carefully sketches a still life compiled in the back of the art room. A college student frustrated with the low speed of his computer transforms a scanned photograph he took with the help of Photoshop. An artist leans over a large canvas in a spacious studio. Her friend stands in a doorway of a gallery contemplating her latest work. What accounts for changes in pictorial behavior that may lead from a play with spilled milk to an art exhibition?