Wolfgang Köhler (1887-1967) was a co-founder of Gestalt psychology whose research on problem solving in chimpanzees challenged the behaviorist view that all learning occurs through gradual trial and error. His work on the Spanish island of Tenerife during World War I, documented in The Mentality of Apes (1917), provided compelling evidence for insight learning — the sudden reorganization of a problem that leads to a solution.
Insight Experiments
Köhler placed chimpanzees in situations where they needed to obtain out-of-reach food by using tools or combining objects in novel ways. In the classic experiments, Sultan (the most gifted chimpanzee) stacked boxes to reach bananas hung from the ceiling, and fitted two short sticks together to create a tool long enough to reach food outside the cage. Critically, the solutions appeared suddenly rather than gradually, often after a period of apparent contemplation, and once achieved, could be immediately repeated — characteristics inconsistent with trial-and-error learning but consistent with insight.
Köhler's insight research challenged Thorndike's view that problem solving is always gradual association formation. Modern research has confirmed that insight is a genuine cognitive phenomenon involving sudden representational restructuring, with distinct neural signatures (increased gamma activity preceding the "aha" moment). Köhler also made important contributions to perceptual organization, isomorphism (the theory that brain processes mirror the structure of perceptual experience), and the scientific integrity of psychology — he was one of few German academics to publicly oppose Nazi interference in university governance.