Gestalt psychology began in Germany in the early 20th century and focused on the idea of "learning by insight". Key founders included Wertheimer, Kohler, and Koffka. Kohler conducted experiments with chimpanzees that demonstrated insight learning. In one experiment, a chimpanzee used boxes to reach a banana hung out of reach, and in another used sticks of different lengths combined to reach a banana outside its cage. The experiments showed that learning could occur through sudden insights into solving problems rather than just trial and error. Teachers should present material in a way that allows students to gain insights into relationships and concepts as a whole rather than focusing only on separate parts.