By the first world war forced into staying on Tenerife, he performed a series of experiments on a German research station there with great apes, particularly chimpanzees.  He observed under more than that sometimes the animal understands the structure of a problem and then also acts to that understanding. After the war he returned to the Berlin University. There he processed the results obtained and insights in a series of lectures, in which he the book The mentality of apes (1948) based (originally: Intelligenzprüfungen an Menschenaffen). Its most important conclusion was that it is very important to have insight and understanding to solve problems.
Known for his introduction of the idea of ' sudden insight '. He suggested that the solution of a problem more often is the result of a sudden flash of insight, rather than a learning process of trial and error.
Köhler also developed the idea of isomorphism (doctrine of the similar form). He wanted to demonstrate that ' gestaltvelden ', which in physical processes in chemistry, electricity and biology play a role, analog of form to gestaltvelden that affect brain processes. A book on the subject of his hand appeared In 1920. Max Wertheimer had this idea already mooted in 1912 in an article about movement. The isomorphism emerged as a physiological counterpart of the ancient concept of the S-R (stimulus-response) links of the nerve cells. Köhler fought for the idea that a process does not expire through coincidentally linked connections (sinnlose Und-verbindungen) and associations in behavior and brain, but that the quality of a whole is greater than the sum of its parts, in fact, that the quality of all the characteristics of the parts (Gestaltqualität) determines.How some functions depends on the place and role in the whole. The course of the entire field process is from within, from that interplay of function and freedom, organized. Analysis would be from understanding the whole need to obtain insight in the function of the share, rather than the other way around, as the behaviorists advocated. Köhler brought forward that order does not have to be a forced situation by machines, but may arise from the mutual dynamics and distribution of orderly forces. He knew to convince many of his ideas through the use of appealing examples from everyday life.
But many others were violently attacked his gestaltdenkbeelden. The gestaltgedachten not with the mechanical, machine-like man tracked down-and worldview, such as that to some extent was adopted by thestructuralism, functionalism, Behaviorism and associationism. Further views on understanding and troubleshooting Köhlers went against the views of William James and John Watson about ' ingrained ' networks of automatic reflexes.
From the isomorphism Köhler in the 1940s and 1950s developed ideas on what he called ' figural aftereffects ', unrealistic perceptions or illusions of observations.
In the meantime he worked steadily to the elaboration of the gestaltprinciples. In 1929 released the book Gestalt psychology.
In the run-up to the second world war, Köhler openly stand against the national socialism. In 1934, he emigrated to the United States and he had to flee. There he received an appointment as lecturer on Harvard, but moved in 1935 to Swarthmore College, that for years he remained faithful. Here he wrote and published more about gestalt psychology. That resulted in two systematic studies: The Place of Value in a World of Facts(1938) and Dynamics in Psychology (1940).
After his retirement he settled in New England, and held office at Dartmouth College. He now had time to go into invitations for speaking engagements and guest lectureships in Europe. Köhler was known as a combative, disciplined and perfectionistic scientist.