<P> The imageless thought debate is often said to have been instrumental in undermining the legitimacy of all introspective methods in experimental psychology and, ultimately, in bringing about the behaviorist revolution in American psychology . It was not without its own delayed legacy, however . Herbert A. Simon (1981) cites the work of one Würzburg psychologist in particular, Otto Selz (1881--1943), for having inspired him to develop his famous problem - solving computer algorithms (such as Logic Theorist and General Problem Solver) and his "thinking out loud" method for protocol analysis . In addition, Karl Popper studied psychology under Bühler and Selz, and appears to have brought some of their influence, unattributed, to his philosophy of science . </P> <P> Whereas the Würzburgers debated with Wundt mainly on matters of method, another German movement, centered in Berlin, took issue with the widespread assumption that the aim of psychology should be to break consciousness down into putative basic elements . Instead, they argued that the psychological "whole" has priority and that the "parts" are defined by the structure of the whole, rather than vice versa . Thus, the school was named Gestalt, a German term meaning approximately "form" or "configuration ." It was led by Max Wertheimer (1880--1943), Wolfgang Köhler (1887--1967), and Kurt Koffka (1886--1941). Wertheimer had been a student of Austrian philosopher, Christian von Ehrenfels (1859--1932), who claimed that in addition to the sensory elements of a perceived object, there is an extra element which, though in some sense derived from the organization of the standard sensory elements, is also to be regarded as being an element in its own right . He called this extra element Gestalt - qualität or "form - quality ." For instance, when one hears a melody, one hears the notes plus something in addition to them which binds them together into a tune--the Gestalt - qualität . It is the presence of this Gestalt - qualität which, according to Von Ehrenfels, allows a tune to be transposed to a new key, using completely different notes, but still retain its identity . Wertheimer took the more radical line that "what is given me by the melody does not arise...as a secondary process from the sum of the pieces as such . Instead, what takes place in each single part already depends upon what the whole is", (1925 / 1938). In other words, one hears the melody first and only then may perceptually divide it up into notes . Similarly in vision, one sees the form of the circle first--it is given "im - mediately" (i.e. its apprehension is not mediated by a process of part - summation). Only after this primary apprehension might one notice that it is made up of lines or dots or stars . </P> <P> Gestalt - Theorie was officially initiated in 1912 in an article by Wertheimer on the phi - phenomenon; a perceptual illusion in which two stationary but alternately flashing lights appear to be a single light moving from one location to another . Contrary to popular opinion, his primary target was not behaviorism, as it was not yet a force in psychology . The aim of his criticism was, rather, the atomistic psychologies of Hermann von Helmholtz (1821--1894), Wilhelm Wundt (1832--1920), and other European psychologists of the time . </P> <P> The two men who served as Wertheimer's subjects in the phi experiment were Köhler and Koffka . Köhler was an expert in physical acoustics, having studied under physicist Max Planck (1858--1947), but had taken his degree in psychology under Carl Stumpf (1848--1936). Koffka was also a student of Stumpf's, having studied movement phenomena and psychological aspects of rhythm . In 1917 Köhler (1917 / 1925) published the results of four years of research on learning in chimpanzees . Köhler showed, contrary to the claims of most other learning theorists, that animals can learn by "sudden insight" into the "structure" of a problem, over and above the associative and incremental manner of learning that Ivan Pavlov (1849--1936) and Edward Lee Thorndike (1874--1949) had demonstrated with dogs and cats, respectively . </P>

Who is considered to be one of the primary figures of early psychology