Gustav Theodor Fechner

German psychologist

• Born: April 19, 1801
• Birthplace: Gross-Särchen, Lusatia (now in Germany)
• Died: November 18, 1887
• Place of death: Leipzig, Germany

Fechner is widely regarded as both the founder of psychophysics—the science of the mind-body relation—and a pioneer in experimental psychology. His most important contributions are a number of quantitative methods for measuring absolute and differential thresholds that are still employed by psychologists to study sensitivity to stimulation.

Early Life

Gustav Theodor Fechner (FEHK-nehr) was the second of five children of Samuel Traugott Fechner and Johanna Dorothea Fischer Fechner. His father was a progressive Lutheran preacher who is said to have astounded the local villagers by mounting a lightning rod on the church tower and by adopting the unorthodox practice of preaching without a wig. Although he died when Gustav was only five years old, already the young Fechner was infused with his father’s fierce intellectual independence and his passion for the human spirit.

Fechner attended the gymnasium at Soran, near Dresden, and was matriculated in medicine at the University of Leipzig in 1817. He was not a model student, opting to read on his own rather than attend lectures. During this period, Fechner became disenchanted with establishment views: He professed atheism and was never able to complete the doctorate that would have entitled him to practice medicine. His studies were not a waste of time, however, because he began composing satires on medicine and the materialism that flourished in Germany during this period. Some fourteen satirical works were published by Fechner under the pseudonym “Dr. Mises” between 1821 and 1876.

In 1824, Fechner began to lecture on physics and mathematics at the University of Leipzig without any remuneration. Translating scientific treatises from French into German (about a dozen volumes in six years), although onerous work, helped him to make a living. He managed to publish numerous scientific papers during this period, and a particularly important paper on quantitative measurements of direct currents finally secured for him an appointment with a substantial salary as professor of physics in 1834.

This period marked the happiest time in Fechner’s life. The year before his appointment, he had married Clara Volkmann, the sister of a colleague at the university. The security of a permanent position and marital bliss did nothing to dampen his enthusiasm for hard work; an enviable social life was simply incorporated into his already cramped schedule. Evenings at the local symphony conducted by Felix Mendelssohn were regular events to which, on occasion, the Fechners were accompanied by Robert and Clara Schumann, his niece by marriage.

Fechner’s idyllic life was shattered in 1839 by an illness that forced him to resign his position at the university. At first, he experienced partial blindness caused by gazing at the sun through colored glasses as part of a series of experiments on colors and afterimages; depression, severe headaches, and loss of appetite soon followed. For three years, Fechner sheltered himself in a darkened room, and his promising career seemed to be over. One day, however, he wandered into his garden and removed the bandages that had adorned his eyes since the onset of his illness. He reported that his vision not only was restored but also was more powerful than before because he could now experience the souls of flowers. After the initial trauma of restored eyesight faded, Fechner recovered with a revitalized religious consciousness. It was this newfound awareness of the importance of the human spirit that marked the beginning of Fechner’s mature period.

Life’s Work

The focal point of Fechner’s work was a deep-seated antipathy toward materialism, or the view that nothing exists except for matter and its modifications. His first volley against materialism was the enigmatic Nanna: Oder, Über das Seelenleben der Pflanzen (1848; Nanna, or the soul life of plants), which advanced the notion that even plants have a mental life. Three years later, his Zend-Avesta: Oder, Über die Dinge des Himmels und des Jenseits (1851; Zend-Avesta: On the Things of Heaven and the Hereafter , 1882) proclaimed a new gospel based on the notion that the entire material universe is consciously animated and alive in every particular. The phenomenal world explored by physics, Fechner asserted, is merely the form in which inner experiences appear to one another. Because consciousness and the physical world are coeternal aspects of the same reality, materialism (or what Fechner referred to as the “night view”) must be repudiated because it examines the universe in only one of its aspects.

More pertinent, Fechner submitted that his alternative “day view” dissolves the traditional problem of the mind-body relation. There is no need to worry about how the physical is converted into the mental, because mind and body are not distinct kinds of things. All that one needs is to display the functional relationship between consciousness and its physical manifestations. Because it was uncontested that physical qualities could be measured, Fechner discerned that he would have to specify a means for measuring mental properties if the scientific establishment was to be convinced that his alternative program represented a legitimate contender to materialism.

The German physiologist Ernst Heinrich Weber had submitted in 1846 that a difference between two stimuli (or an addition to or subtraction from one or the other stimulus) is always perceived as equal if its ratio to the stimulus remains the same, regardless of how the absolute size changes. If a change of one unit from five can be detected, Weber’s result specifies that so can a change of ten from fifty, of one hundred from five hundred, and the like. On the morning of October 22, 1850, Fechner discovered what he regarded as the fundamental relation between the mental and the physical world. Where Weber’s result was restricted to external stimulation, Fechner posited a general mathematical relationship between stimulus and sensation, such that for every increase in stimulation there is a corresponding increase in sensation. This functional relationship is now known as the Weber-Fechner law. It asserts that the psychological sensation produced by a stimulus is proportional to the logarithm of the external stimulation.

Although Fechner’s law represents a development of Weber’s work, he did not rely on Weber’s substantive result. Indeed, it was Fechner who realized that his psychophysical principle corresponded to Weber’s result and gave it the name Weber’s law. Perhaps he was overly generous. Weber’s result conflicts with low-stimulus intensities. By incorporating the activity of the subject’s sensory system into the equation, Fechner was able to overcome this difficulty.

Fechner’s law is a genuine psychophysical law in the sense that it relates mental phenomena to external stimulation. Comparing it with Sir Isaac Newton’s law of gravitation, Fechner laid out his ambitious program for a science of the functional relations of mind and body in his classic work, Elemente der Psychophysik (1860; Elements of Psychophysics , 1966). Along with his method for measuring the relationship between psychological and physical phenomena, Fechner refined three methods—the method of barely noticeable differences, the method of right and wrong cases, and the method of average error—for measuring thresholds, or the point at which a stimulus (or a stimulus difference) becomes noticeable or disappears. These techniques for measuring sense discrimination are still prominent in psychological research. Fechner also established the mathematical expressions of these methods and contributed to the literature a series of classical experiments on human sensitivity to external stimulation.

Fechner’s program for a psychophysics attracted few converts. Vocal opponents, such as William James, the eminent American philosopher and psychologist, objected that mental properties are not quantifiable. Fechner sought to measure sensations by measuring their stimuli, but he furnished no independent evidence for the presupposition that it is sensations that are measured. This objection was significant granted that there was good reason to suppose that sensations cannot be measured. Sensations are not additive; a larger sensation is not simply a sum of smaller sensations. Anything that is not additive, Fechner’s opponents declared, cannot be measured. What he had measured, rather, was observer response to stimulation; Fechner had produced an account of sensitivity and so had confused the sensation with the excitation of the subject.

These and related objections led to the downfall of psychophysics. Although Fechner’s ideas were examined by Hermann von Helmholtz, Ernst Mach, and other scientists who were interested in related subjects, Fechner’s attempt to place the mental on a par with the physical was dismissed as pure whimsy. The failure of Fechner’s program, however, does not diminish his importance as a philosopher. Fechner’s methods for measuring sensitivity were assimilated into the basis of empirical psychology. Because Fechner’s methods presume that chance is a characteristic of physical systems, Fechner achieved a measure of victory over materialism. If he was right, mental phenomena could not be straightforwardly reduced to matter and its modifications.

Although Fechner continued to contribute to the literature on psychophysics, he turned to other matters late in his life. An interest in aesthetics proved to be a rather natural development of his interest in stimulation and his long-standing affection for the arts. The culmination of his work on the study of beauty was Vorschule der Aesthetik (1876; introduction to aesthetics), which argued that aesthetics is the study of the objects that produce aesthetic experiences. This work proved to be seminal in the history of experimental aesthetics.

Significance

Gustav Theodor Fechner was a man of great erudition—not only was he a physicist and a philosopher but he also was the author of a detailed theological theory, a poet, and a satirist. What united his diverse pursuits was a struggle to reconcile the empirical rigor of the exact sciences with a spiritual conception of the universe. Although Fechner’s attempt to place consciousness on a par with the physical was rejected by the scientific community, his vision helped to lay the foundations for the emerging science of empirical psychology.

Fechner’s greatest contributions, the functional proportion between sensation and stimulus and his numerous techniques for measuring psychological response to stimulation, do not compare favorably with the concept of universal gravitation. Fechner’s philosophy of nature as consciously animated and alive in every particular was rejected by the scientific community, and so his contributions did not revolutionize science. However, without his techniques for measuring psychological variables, the science of empirical psychology would not have reached maturity.

Bibliography

Boring, Edwin G. A History of Experimental Psychology. 2d ed. New York: Appleton-Century-Crofts, 1950. A comprehensive account of the emergence of experimental psychology. Although Boring credits Fechner with laying the foundations for empirical psychology, he contends that it was merely an unexpected by-product of Fechner’s philosophical interests.

Fechner, Gustav Theodor. Elements of Psychophysics. Translated with a foreword by Helmut E. Adler. New York: Holt, Rinehart and Winston, 1966. The author’s introduction provides an overview of the problem concerning the mind-body relation and an outline of his program for a science of psychophysics. The translator’s foreword places Fechner’s contributions in their nineteenth century historical context.

Heidelberger, Michael. Nature from Within: Gustav Theodor Fechner and His Psychophysical Worldview. Translated by Cynthia Klohr. Pittsburgh: University of Pittsburgh Press, 2004. A biography that includes a detailed examination of Fechner’s writings. Heidelberger views Fechner’s work from three perspectives: history, philosophy, and what Fechner called his “day view” approach of studying across fields.

James, William. The Principles of Psychology. New York: Henry Holt, 1890. Reprint. New York: Dover, 1950. Contains a faithful presentation of Fechner’s contributions and a searching critique of his philosophical outlook. Perhaps the best indicator of why psychophysics fell into disfavor.

Savage, C. Wade. The Measurement of Sensation: A Critique of Perceptual Psychophysics. Berkeley: University of California Press, 1970. A thorough discussion of the central philosophical issues in the measurement of sensation. The excellent bibliography is a useful guide to the wealth of literature on this topic.

Snodgrass, Joan Gay. “Psychophysics.” In Experimental Sensory Psychology, edited by Bertram Scharf. Glenview, Ill.: Scott, Foresman, 1975. A concise introduction to the history of psychophysical theory and its methods. For the technically minded reader, the analysis of the relationship between Weber’s result and Fechner’s psychophysical law helps to illustrate Fechner’s contributions to the measurement of sensation.