Wolfgang Köhler (1887–1967) was one of Wertheimer’s closest associates. From 1913 to 1920, Köhler was director of the Anthropoid Research Station on the island of Tenerife, which is in the Canary Islands off the coast of Northwest Africa. He had intended to stay in Tenerife for only a short while. With the outbreak of World War I, however, he was unable to leave for several years. While in Tenerife, Köhler conducted an important series of studies on chimpanzees’ problem-solving behavior. He set up rooms where bunches of bananas were placed just out of the chimpanzees’ reach and then watched how they solved the problem of reaching the bananas.

Although not all chimpanzees were able to successfully solve the problem—evidently chimpanzees, like human beings, vary in their intelligence—those that did so exhibited similar behavior. For one, they would often try to reach the bananas simply by jumping or reaching for them. Upon failing to grasp the bananas, they would often show frustration, screaming, or kicking the walls of the room. Eventually, after surveying the entire room, they would suddenly derive a solution involving the use of nearby objects as tools. One chimp might drag a box under the bananas and then climb on top of it to reach them. Some chimps stacked multiple boxes to attain their goal. Another might put two sticks together to create a stick long enough to reach the food.