Gestalt psychology is a school of psychology which began in the early part of the twentieth century as a reaction against the behavioural psychology of Pavlov and Watson and insisted that psychological phenomena should be treated as Gestalten which could not be equated with the elements that made them up. The first Gestalt psychologists Kafka, Kohler and Wertheimer, arrived at their ideas after studies of perception; they were struck by the way the brain organized dots of light into visual patterns or musical notes into melodies. Kohler later branched out into studies of insight learning in apes and later Gestaltists like Goldstein and Lewin have extended Gestalt ideas into areas of personality and social psychology. Gestalt thinking on perception is now largely accepted by psychologists, and its approach is very much in tune with the cognitive revolution, though some people would argue that there are areas of human behaviour which can still best be understood by an analysis of the elements involved.