<P> Oswald Külpe is the main founder of the Würzburg School in Germany . He was a pupil of Wilhelm Wundt for about twelve years . Unlike Wundt, Külpe believed experiments were possible to test higher mental processes . In 1883 he wrote Grundriss der Psychologie, which had strictly scientific facts and no mention of thought . The lack of thought in his book is odd because the Würzburg School put a lot of emphasis on mental set and imageless thought . </P> <P> The work of the Würzburg School was a milestone in the development of experimental psychology . The School was founded by a group of psychologists led by Oswald Külpe, and it provided an alternative to the structuralism of Edward Titchener and Wilhelm Wundt . Those in the School focussed mainly on mental operations such as mental set (Einstellung) and imageless thought . Mental set affects perception and problem solving without the awareness of the individual; it can be triggered by instructions or by experience . Similarly, according to Külpe, imageless thought consists of pure mental acts that do not involve mental images . An example of mental set was provided by William Bryan, an American student working in Külpe's laboratory . Bryan presented subjects with cards that had nonsense syllables written on them in various colors . The subjects were told to attend to the syllables, and in consequence they did not remember the colors of the nonsense syllables . Such results made people question the validity of introspection as a research tool, and let to a decline of voluntarism and structuralism . The work of the Würzburg School later influenced many Gestalt psychologists, including Max Wertheimer . </P> <P> Experimental psychology was introduced into the United States by George Trumbull Ladd, who founded Yale University's psychological laboratory in 1879 . In 1887, Ladd published Elements of Physiological Psychology, the first American textbook that extensively discussed experimental psychology . Between Ladd's founding of the Yale Laboratory and his textbook, the center of experimental psychology in the US shifted to Johns Hopkins University, where George Hall and Charles Sanders Peirce were extending and qualifying Wundt's work . </P> <P> With his student Joseph Jastrow, Charles S. Peirce randomly assigned volunteers to a blinded, repeated - measures design to evaluate their ability to discriminate weights . Peirce's experiment inspired other researchers in psychology and education, which developed a research tradition of randomized experiments in laboratories and specialized textbooks in the 1800s . The Peirce--Jastrow experiments were conducted as part of Peirce's pragmatic program to understand human perception; other studies considered perception of light, etc . While Peirce was making advances in experimental psychology and psychophysics, he was also developing a theory of statistical inference, which was published in "Illustrations of the Logic of Science" (1877--78) and "A Theory of Probable Inference" (1883); both publications that emphasized the importance of randomization - based inference in statistics . To Peirce and to experimental psychology belongs the honor of having invented randomized experiments, decades before the innovations of Jerzy Neyman and Ronald Fisher in agriculture . </P>

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