MÜLLER, GEORG ELIAS (1850-1934)

During his tenure at the University of Göttingen from 1881 to 1921, the German psychologist Georg Elias Müller helped to spearhead major advances in theory and research into perception, learning, and memory.

Early Life and Career

Georg Elias Müller was born on July 20, 1850, into a clerical family in Grimma, Saxony, Germany. As a schoolboy he showed a precocious interest in natural science, philosophy, poetry, and history. In 1868 he began to study philosophy and history at the University of Leipzig and moved to the University of Berlin in 1869. In Berlin he became acquainted with Rudolph Hermann Lotze's writings, which shifted his focus from history to science as the subject closest to his principal interest, philosophy. After interrupting his studies to fight in the Franco-Prussian war of 1870-1871, he moved to Göttingen in 1872 to study with Lotze. The following year he submitted his doctoral dissertation on sensory attention (Müller, 1873) and he completed his postdoctoral dissertation on psychophysics (Müller, 1878) in 1876. Five years later he succeeded Lotze as chair of philosophy in Göttingen, a position he held for forty years, until his mandatory retirement in 1921.

By then Müller's institute had become one of the most important centers for experimental psychology in all of Europe, attracting students from all over the world. He also opened his laboratory to women at a time when research opportunities for women were nearly nonexistent. Among his students were Alfred Binet, E. R. Jaensch, Adolf Jost, David Katz, Oswald Kroh, Oswald Külpe, Lillian J. Martin, Eleanor McGamble, Alfons Pilzecker, Géza Révész, Edgar Rubin, and Friedrich Schumann. Müller, who was often described as a somewhat gruff character, was feared by his students as a relentless critic and a stickler for scientific rigor, but he was also cherished as a skillful listener and as an unfaltering supporter of their work. His meticulous, diligent, and innovative experimental approach earned his laboratory the reputation as the premier center for experimental psychology in all of Europe. Müller's pioneering vision also led to the formation of the "Society for Experimental Psychology," which he headed from 1904 to 1927.

Main Work

Müller's main contributions to experimental psychology fall into three areas: psychophysics, visual perception, and memory.

Psychophysics

Working from the philosophical background of the mind-body problem, which energized his research all his life, Müller first directed his attention to psychophysics, the scientific discipline that spear-headed the establishment of psychology as an objective science. The Weber-Fechner law, which describes the relationship between physical and perceived stimulus intensity, had appeared in Gustav Fechner's groundbreaking work "Elements of Psychophysics" in 1860. While the idea of a lawful relationship between physical objects and perceived stimuli had been widely accepted, the experimental methods for obtaining measurements and the possibility of a mathematically precise treatment of subjective perceptions were the subject of extended scientific debate. Müller's postdoctoral dissertation, "On the Foundations of Psychophysics" (1878), and his paper on the method of right and wrong cases (later known as the method of constant stimuli) established Müller as an independent, critical thinker. His contributions were acknowledged in Fechner's "Revision of the Main Points of Psychophysics." His methods still are widely used in psychophysical experiments.

Visual Perception

Visual perception, especially color perception, occupied Müller in the late 1890s and led to his authoring four publications on this topic between 1896 and 1897. In these papers he argued that the three photochemical substances proposed by Ewald Hering as the basis of color vision were reversible by a chemical rather than a metabolic process. Moreover, he proposed that equal excitation by red/green, blue/yellow, and black/white resulted in the perception of "cortical gray" rather than the visual "silence" assumed by Hering. Müller returned to color perception after his retirement and remained with it until his final years, even at the expense of completing his autobiography. Instead, he summarized his observations and theories in two books: On Sensations of Color: Psychophysical Investigations (1930) and Brief Contributions to the Psychophysics of Color Sensations (1934).

Memory

Müller's work on memory is probably his best known. He inherited the topic from Hermann Ebbinghaus, whose monograph On Memory (1885) first demonstrated that even cognitive phenomena such as verbal memory could be successfully studied and quantified in the laboratory. When Ebbinghaus showed no further interest in memory research, Müller seized the opportunity. During the next thirty years Müller and his students made a number of seminal contributions. The most notable were "Experimental Contributions to the Investigation of Memory" (1894) and "Experimental Contributions to the Theory of Learning and Memory" (1900). Both articles describe sophisticated experimental methods for studying verbal memory, which were developed by Müller and his students Friedrich Schumann, Adolf Jost, and Alfons Pilzecker and became standard in experimental psychology for many decades.

Müller's first contribution was to recognize the importance of constructing lists of syllables that were equally difficulty to read and learn. To this end he tightened Ebbinghaus's rules for generating and selecting nonsense syllables. Müller's second contribution was to control the presentation of study material. Lists of syllables were mounted on a rotating cylinder, called a memory drum, and syllables were presented one at a time through a shutter behind which the memory drum was mounted. The subjects were instructed to respond by reading each syllable aloud with emphasis on every odd-numbered syllable, thus creating paired associates (pairs of emphasized and nonemphasized syllables, or trochees).

Müller and Schumann first adopted Ebbinghaus's method of determining how many trials were needed to memorize a list of twelve syllables (the method of complete mastery, or Erlernungsmethode). They then explored the conditions under which previously learned material facilitated the memorization of reorganized syllable lists (the method of savings, or Ersparnismethode). Using these methods, they determined that reading the pairs of syllables in trochaic style resulted in stronger associations between the syllables within the pair than between the adjacent syllables of two pairs. They also explored a number of conditions (e.g., retention delay) that either facilitated or weakened acquisition of the study material.

Müller and Pilzecker significantly improved on these early experiments by replacing the method of complete mastery with the method of right associates (Treffermethode), shifting the focus from acquisition to recall of learned material. In these experiments the number of learning trials for each list of syllable pairs was fixed. Then the subjects were cued with the first syllable of each pair and asked to recall the second syllable of each pair. This method, developed by Adolph Jost in Müller's laboratory, provided three ways to assess memory performance: correct answers, incorrect answers, and failures to recall. Moreover, the data could be supplemented by the subject's response times as measured by a novel apparatus. The shutter in front of the memory drum was now operated by an electromagnet. Opening the shutter exposed the cue syllable for each trial and triggered a chronometer. The subject's response was registered by a lip key or vibration-sensitive device that would stop the chronometer, close the shutter, and advance the memory drum to the next cue syllable. Armed with this methodology, Müller and Pilzecker began a series of experiments that quickly exceeded the scope of Ebbinghaus's original studies. After studying the effects of list repetition and retention interval on cued recall, they explored interference between associations. They first presented a pair of syllables (e.g., ser-lad) and in a later list used the same cue syllable (ser) in another association (e.g., ser-kum). Recall cued by ambiguous syllables was consistently lower than recall cued by unambiguous syllables.

These findings became fundamental to learning and memory research. Yet Müller's monograph with Pilzecker is probably best known for its novel proposal that learning does not induce instantaneous, permanent memories but that memory requires an interval of consolidation. He and Pilzecker arrived at that conclusion after a number of experiments on retroactive inhibition, a painstaking analysis of the types incorrect answers volunteers were prone to make, and a thoughtful consideration of a phenomenon they termed "perseveration" (i.e., the tendency of study material to inger in a subject's mind after learning). They wrote (Müller and Pilzecker, 1900, 196-197):

After all this, there is no alternative but to assume that, after a list of syllables has been read, certain physiological processes that serve to strengthen the associations induced during reading of that list continue with decreasing intensity for a period of time. These processes and their facilitating effects on these associations are being weakened to a greater or lesser extent if the experimental subject experiences further mental exhaustion immediately after reading a list. … It seems justified to suppose that the physiological processes mentioned her are the same that underlie perseverative tendencies. … Mental exertion in an experimental subject after reading a list of syllables has, first, the direct effect of weakening the perseverative tendencies of these syllables and, second, because the effect of these perseverative tendencies is to consolidate syllable associations, the additional effect of impairing these associations (retroactive interference).

Considering their observations on perseveration, Müller and Pilzecker proposed that consolidation occurred within about ten minutes. Yet their experiments did not systematically explore this time course. McDougall and Burnham quickly recognized the idea of memory consolidation because it provided a way to understand temporally graded retrograde amnesia that results from traumatic head injury. Later, Carl Duncan's experiments on ECS-induced retrograde amnesia in rats launched decades of research in many laboratories to study consolidation and its time course.

With the passing decades, awareness of Müller's importance to the field of experimental psychology, especially memory research, began to fade. But his groundbreaking experiments on memory still inspire productive research in cellular neurobiology and systems neuroscience.

An indefatigable scholar, Müller worked long after his retirement in 1921, producing important publications until his death, on December 23, 1934.

Bibliography

Boring, E. G. (1950). History of experimental psychology. New York: Appleton-Century-Crofts.

Burnham, W. H. (1903). Retroactive amnesia, illustrative cases and a tentative explanation. American Journal of Psychology 14, 382-396.

Duncan, C. P. (1949). The retroactive effect of electroshock on learning. Journal of Comparative Physiological Psychology 42, 32-44.

Ebbinghaus, H. (1885). Über das Gedächtnis, Untersuchungen zur experimentellen Psychologie [On memory, Investigations in experimental psychology]. Leipzig: Duncker and Humbolt.

Fechner, G. (1860). Elemente der Psychophysik [Elements of psychophysics], 2 vols. Leipzig: Breitkopf and Härtel.

—— (1882). Revision der Hauptpuncte der Psychophysik [Revision of the main points of psychophysics]. Leipzig: Breitkopf and Härtel.

Haupt, E. J. (1998). Origins of American psychology in the work of G. E. Müller, classical psychophysics and serial learning. In R. W. Rieber and K. Salzinger, eds., Psychology Theoretical-Historical perspectives, 2nd edition. Washington, DC: American Sociological Association.

Jost, A. (1897). Die Associationsfestigkeit in ihrer Abhängigkeit von der Verteilung der Wiederholungen [The strength of associations in relation to the distribution of repetitions]. Zeitschrift für Psychologie 14, 436-472.

Lechner, H. A., Squire, L. R., and Byrne, J. H. (1999). 100 years of consolidation—remembering Müller and Pilzecker. Learning and Memory 6, 77-87.

McDougall, W. (1901). Experimentelle Beitraege zur Lehre vom Gedaechntis, von G. E. Mueller und A. Pilzecker [Experimental contributions to the theory of memory by G. E. Mueller and A. Pilzecker]. Mind 10, 388-394.

Müller, G. E. (1873). Zur Theorie der sinnlichen Aufmerksamkeit [On the theory of sensory attention]. Ph.D. diss. Leipzig: Edelman.

—— (1878). Zur Grundlegung der Psychophysik [On the Foundations of Psychophysics], Vol. 4: Kritische Beiträge. Bibliothek für Wissenschaft und Literatur. 23 vols. Philosophische Abtheilung. Berlin: Greiben.

—— (1879). Über die Maasbestimmung des Ortsinnes der Haut mittels der Methode der richtigen und falschen Fälle [On the quantification of the location sense of the skin by way of the method of right and wrong cases]. Pflüger's Archiv für die gesamte Physiologie 19, 191-235.

—— (1930). Über die Farbenempfindungen, Psychophysische Untersuchungen. Band 1 und 2 [On Sensations of Color, Psychophysical Investigations]. Zeitschrift für Psychologie, Ergänzungsband 17 and 18. Leipzig: Barth.

—— (1934). Kleine Beiträge zur Psychophysik der Farbempfindungen [Brief Contributions to the Psychophysics of Color Sensations]. Leipzig: Barth.

Müller, G. E. and Pilzecker, A. (1900). Experimentelle Beiträge zur Lehre vom Gedächtnis [Experimental contributions to the theory of memory]. Zeitschrift für Psychologie, Ergänzungsband 1, 1-300.

Müller, G. E., and Schuman, F. (1894). Experimentelle Beiträge zur Lehre vom Gedächtnis [Experimental contributions to the investigation of memory]. Zeitschrift für Psychologie 6, 81-190, 257.

Sprung, L., and Sprung, H. (2000). Georg Elias Müller and the beginnings of modern psychology. In G. A. Kimble and M. Wertheimer, eds., Portraits of pioneers in psychology, Vol. 4. Mahwah, NJ: Erlbaum.

Hilde A. E.Lechner