Max Wertheimer (1880–1943) is recognized as the father of Gestalt theory. His interest was first piqued when he noticed the illusion of motion while sitting on a train. Although the landscape outside the train was stationary, it seemed to be moving backwards as the train sped by. Most of us have had the same experience. To Wertheimer, however, this phenomenon offered a unique window into the workings of the mind. When he began his investigations at the University of Frankfurt in 1910, two slightly younger psychologists, Wolfgang Köhler (1887–1967), and Kurt Koffka (1886–1941) came to work with him. Together they studied the illusion of movement through various experiments. Their research into the phi effect, as Wertheimer named it, was the beginning of a life-long, shared commitment to Gestalt research and theory. By the mid-1930s, all three men had relocated to the United States, Koffka before Hitler’s rise to power, and Wertheimer and Köhler in direct response to it.