CHAPTER 13

Chapter 13

FECHNER: PSYCHOPHYSICS

Psychology would emerge in the 1880's as an independent, scientific and academic discipline. It claimed philosophy and physiology as its progenitors, although it has been argued that psychology was born of phrenology out of wedlock with science. Whatever the origins, before psychology could take the essential step to stand on its own as an independent, scientific discipline, it had to demonstrate how the scientific method could be applied to its subject-matter. Both physiology and philosophy had demonstrated their own methods for studying what we have defined as psychological thought. Kant had said that psychology could not be a natural science because it could not be mathematical, it could not analyze its data and so could never be experimental. While Herbart had demonstrated the possibility of quantitative treatment of psychological concepts, psychology still lacked a clearly defined set of procedures such as those followed by physics and physiology that would allow it to be experimental. Without an experimental methodology, psychology would likely have remained only a subdivision of philosophy.

It is to G. T. Fechner that we owe much credit for laying the basis for the application of the experimental method to psychology. His establishment of psychophysics through his publication of Elements of Psychophysics in 1860 is a major landmark in the transition of psychology from a scattered set of subject-matters found in several disciplines to a relatively coherent discipline centered on the laboratory. There is some question as to the degree that Fechner intended such an outcome, however, since his interests were not particularly in system building or discipline building.

Engrossed in philosophical and mystical interests, Fechner devoted several periods of his long life to speculation and to the investigation of what seemed to him the most fundamental problem of life--psychophysics, or the quantitative investigation of the functional interrelations of body and mind.[1] In spite of the arid quality of his psychophysical studies, his writings reveal a burning enthusiasm for grappling with the very nature of man.

Life and Careers of Fechner

Gustav Theodor Fechner was born in 1801 in a small village in the Wendish country of southeastern Germany.[2] His father was a Lutheran preacher, who died when Gustav was five years old, but not before he had given his son a grounding in Latin. After attending the Gymnasium, Fechner in 1817 matriculated at the University of Leipzig, an association that was to last for seventy years. He took his degree in medicine in 1822, but he decided against going into practice.

Even early in his career there were some glimmerings of humanistic interests. Under the pseudonym of Dr. Mises, he employed the weapon of satire against views with which he disagreed. The first of these satirical pieces appeared in 1821, before his graduation; it was directed against the medical fad at that time of using iodine for just about any ailment and was called, Proof that Man is Made of Iodine. Occasional satirical pieces continued to come from his pen. Earlier in the century, there had been in Germany a resurgence of interest in materialism or mechanism. To Fechner, materialism was a theory devoid of truth, and several of his satires were devoted to attacking the view that the universe is inert matter--the "night view," as he called it--and to a defense of the position that the universe can be regarded from the point of view of consciousness--the "day view."

This antimechanist position was to be a fixed point in what otherwise appears to be a series of shifts of interest during Fechner's life. According to E.G. Boring, between 1817, when Fechner started medical school, and his death in 1887, Fechner was successively a physiologist, a physicist, an aestheticist and, throughout most of the later years, a philosopher.[3] Following his aim steadfastly through these careers, he founded psychophysics, which in turn supplied the methodological tools necessary for the founding of laboratory - oriented experimental psychology.

After graduation in medicine he began his second career by studying physics. In 1824, after a period without official appointment, he started to lecture on this subject and to conduct laboratory investigations in electricity. In 1833 he married and the following year, when only thirty-three years old, he became a professor of physics. His academic future seemed secure. During these years sheer economic necessity had led him into translating various French scientific works that served to add to his scientific knowledge; however, some of his means of increasing his income amounted to hack work, such as editing and writing a considerable share of an encyclopedia of household knowledge in eight volumes. He broke under the strain of work and became a "nervous invalid." In general, this could be characterized as a neurotic depression with pronounced hypochondriacal features.

In the winter of 1839-40, a painful eye disorder developed, and he resigned his chair in physics. Fechner had studied after-images by staring into the sun, which undoubtedly aggravated the condition, if it did not bring it on. Years of suffering followed. His eyes were so hypersensitive to light that he could not leave the house without bandaging them, and for the rest of his life he had to curtail his reading. Sometimes for weeks on end he could not eat at all; he eventually found that fruit, strongly spiced raw ham, and wine could be tolerated. He could not talk for long periods and he thought of suicide. Some slight improvement occurred late in 1843, but it was thought there was no chance of his regaining his health. In 1844, he received a small pension from the university, thus establishing officially his position as an invalid. However, hardly one of his remaining forty-four years went by without some serious contribution from his pen. There is no doubt that he really suffered, so it would be unfair to apply to him that grand phrase, "he enjoyed poor health."

His inability to use his eyes resulted in many hours spent in contemplation. This reinforced his speculative turn of mind, which came to the fore as soon as he was able to resume working. He now entered the third phase of his career and became a psychophysicist with philosophical leanings.

The reason for his inclusion among the great psychologists lies in his connection with psychophysics. Reserving details for later systematic and methodological discussion, it suffices to say that he became interested to the point of obsession in demonstrating that mind and body are aspects of a unity.[4] Since matter (body) is not to be denied any more than consciousness (mind), the two must be reconciled and made one. Fundamentally, to Fechner, the difference between mind and body, the dualism that some find, is nothing more than a difference in point of view concerning the psychophysical entity. The mind is related to the body as the inside of a circle is related to the outside. This makes his view a double-aspect theory, or a psychophysical monism -- mind and body are but two aspects of a fundamental unity. Since the two aspects are identical, the view is also referred to as the "identity hypothesis."

The solution, he tells us, came with dramatic suddenness on the morning of October 22, 1850.[5] In bed, "before getting up," he realized that the law of the connection between body and mind is to be found in a statement of the quantitative relations between mental sensation and bodily stimulus, not in simple proportion, but such that increases in the former correspond to proportional changes in the latter.

Ten years later, his Elemente der Psychophysik appeared. Here he discusses the functional relations of mind and body and reported investigations of his own and others on the various senses--sight, sound, and the cutaneous and muscular senses.

Some conception of Fechner's intent to measure psychological functions can be gained by turning to his next undertaking, the study of experimental esthetics, another field he founded. Fechner had a deep and long-standing interest in art. His first paper in this new career appeared in 1865 and dealt with the "golden section," the most aesthetically pleasing relation of length to breadth in an object. Here again, Fechner applied his exact method to a global goal. He rebelled against the attempt to develop an esthetics "from above down" by formulating abstract principles of beauty by which to judge the concrete object, in the manner of the Romanticists. Instead, he believed one must start with simple figures. In order to find the linear proportions an artist used, he patiently measured the dimensions of pictures, cards, books, snuff boxes, writing paper, windows--in fact, any object that was purported to have esthetic appeal. Thus he sought to develop an experimental esthetics "from below."

Fechner also became very much involved in a cause celebre of his day concerning the authenticity of two paintings of the Madonna, each attributed to Holbein. Although very similar, they differed in detail, and the authenticity of each was in dispute. Fechner inclined to the opinion that both were authentic. There was also a dispute over which was the more beautiful. Taking advantage of an exhibition in which both were exhibited together, he launched what may have been the first public opinion poll. He made arrangements for the public to be invited to record comments in a book placed alongside the paintings. Sparseness of returns with a disproportionate number from art critics, who had already formed opinions, made this particular venture a failure.

His major book on esthetics, Vorschule der Aesthetik,[6] appeared in 1876. Its appearance also served to close his participation in esthetics. Experimental psychology as represented by Wilhelm Wundt, now also at Leipzig, and the intense interest of many others, protagonists as well as antagonists, would not leave Fechner in peace to pursue his still strong philosophical interests. He was drawn back to a second career in psychophysics, which lasted until his death in 1887.

The Aim of Fechner

The careers through which Gustav Fechner moved did not reflect a change in fundamental interest. His guiding aim was a search for an answer to an all-consuming question--the nature of the relationship between the spiritual and material worlds. He sought a unified conception of body and soul that, while based on mystical speculation, also had a scientific basis.

In the spirit of Plotinus, his spiritual ancestor of seventeen centuries before, Fechner saw the world as a system of souls appearing to each other as bodies. His mystical strain was reflected in the very title of one of his works, Zend-Avesta, On the Things of Heaven and the Hereafter.[7] In this book, Fechner endowed all things with personal souls. The world is made up of external manifestations, bodies that are correlated with internal animate realities, souls. This is panpsychism, a theory of the world that endows plants as well as animals with some rudimentary kind of soul. Its relation to primitive animism is direct and obvious. But Fechner was no simple throwback to primitive views. He argued these and related problems with subtlety and enthusiasm.

Consonant with the two major influences that affected him, Fechner sought precise confirmation of these speculations. His was a nature that asked for a relation between poetical and speculative world-views, to be demonstrated by means of precise measurement. He made the mystical aspect his goal, to find the relationship between body and soul and the scientific aspect his method.[8] Psychophysics was one way to approach the relationship.

The starting-point for measurement of physical stimulus and mental sensation Fechner found in the research of E. H. Weber, who was also at Leipzig.

The Influence of Weber

Ernst Heinrich Weber (1795-1878) had been appointed Dozent in physiology at the University of Leipzig in 1817, the same year Fechner arrived as a medical student.[9] The next year he was appointed Professor of Anatomy, and later in his career was made Professor of Physiology. For many years Weber and Fechner moved in the same academic circles and lived in the same community.

As a physiologist, Weber was particularly interested in touch and in the muscle sense, hitherto relatively neglected fields of research.[10] He wished to find smallest discriminable difference between weights, the so-called just noticeable difference. Their task was simple. On each trial subjects lifted two weights, one a standard weight, the other a comparison weight. On each subsequent trial the comparison weight was increased in small gradations. The subjects reported when the comparison weight felt heavier. For a standard weight of, say, forty ounces, it would take a comparison weight of forty-one ounces to be discriminated as heavier. This would produce a just noticeable difference (JND) of one ounce. If the standard weight were eighty ounces, however, it would take not eighty-one ounces to be noticed as heavier as the JND would indicate but eighty-two, a JND of two ounces. Weber found that it was not the absolute difference in weight that led to the discrimination, but the ratio of the JND to the standard weight. In this case, the ratio was one-fortieth. So, if the standard weight were set to twenty ounces, one would expect a twenty and one-half ounce weight to be discriminated as heavier, a JND of half an ounce but still a ratio of 1/40. This was the case.

Weber found that the same phenomenon was found with passive weights, weights placed on the skin rather than being lifted as in the previous experiment. The increase required for a weight to be discriminated as different was not absolute but was in a ratio. This time it was one-thirtieth instead of one-fortieth. The ratio of the change required to be discriminated to the standard stimulus was found to differ from one sense-department to another, but remained constant within a given sensory situation. Weber also tested capacity to discriminate length of lines and marshalled evidence on differences in the pitch of tones. He again found constant ratios. These ratios were found to hold except for extremes. The ratio's broke down for very small standard stimuli or very intense.

Fechner reformulated Weber's ratio into the equation:

dR/R = K

in which dR is the just noticeable stimulus increment, K is a constant, and R is the standard stimulus magnitude. In other words, when divided by the magnitude of the standard stimulus, a stimulus increment required to give a just noticeable difference gives a constant value. As the standard increases, the stimulus required for a JND increases proportionately. This relationship is called Weber's law or Weber's fraction. This fraction and Weber's measurement of just noticeable differences, the JND, is arguably the first quantitatively determined measurement of a mental event.

Fechner's Psychophysics

Fechner construed Weber's results to mean that one could measure sensation as well as the sensory stimulus and state the relation between the two in the form of an equation.12 Fechner went on to devise more generalized formula which he also tried to give Weber's name. This more generalized final equation, given below, has since been called Fechner's law.

Fechner's law states the relationship between the growth of a physical stimulus and the psychological experience of its growth. The result of Fechner's manipulation of Weber's law was the equation S = K log R in which S is the perceived magnitude of the sensation, K is a constant, and R is the physical magnitude of the stimulus. Fechner's law infers a logarithmic relationship between the growth of physical and psychological magnitudes.

Sensation had been measured, and the identity hypothesis, his mind-body parallelism, so Fechner thought, had been demonstrated. He had found the proof for his identity hypothesis in a table of logarithms!

Fechner's work on discrimination was what psychophysicists called the difference threshold, which, along with the absolute threshold (the lowest stimulus magnitude that can be detected) and the terminal threshold (the highest level of a stimulus, such as frequency) that can be detected) are the three fundamental measures of classical psychophysics. In the course of his research, Fechner developed one and systematized two other of the three major methods of classical psychophysics. These three are the method of limits, the method of average error, and the method of constant stimuli. The method of average error that Fechner developed along with his brother-in-law is the most fundamental and will be used as an illustration. The subject himself adjusts a variable stimulus so as to fulfill the instructions given him--for example, to make one line appear equal to the length of a standard line. Before him he sees a length of line, the standard. Another line is to be adjusted by him to be as close to the standard in length as he can make it. No matter how closely he approximates the line, however, an error, large or small, will be made. Sometimes he makes the line too long, sometimes too short, but he always makes some error. After many trials, the average of his errors is found, the so-called average error.

After publication of the Elemente in 1860, interest was immediate, intense, and widespread. Many others, seeing the value of Fechner's work, proceeded to carry out similar experiments. Various controversies raged over one aspect or the other of Fechner's formulations, but the use of psychophysical methods would be fundamental to the creation of experimental psychology. Ironically, with all the excitement his findings engendered, little attention was paid to Fechner's goal for psychophysics, that is, his attempt to find the relationship between body and soul.

Fechner was not interested in what psychophysics became. Other researchers such as Wilhelm Wundt and the students of the Leipzig laboratory, as well as other, developed psychophysics to the study of changes in the physical world that could be lawfully related to changes in sensations, perceptions and judgments.

Sensory psychology was put on a quantitative basis with the introduction of Fechnerian psychophysics. Psychophysics gave a quantitative expression to measurement of the mind. No longer could it be argued that mind could not be measured, or that mathematics could not be applied to its research study. Quantitativism and the refinement of empiricism as expressed in a positive attitude toward experiment would hereafter be characteristic of the psychologists to come.

Summary

Fechner's psychophysics was his attempt to find a scientific relationship between body and soul. He failed to do that, but in the attempt, he devised the basic methodology that would allow mental events to be measured quantitatively. He was influenced by E. H. Weber, whose work on discriminability of weights led to the formulation of Weber's law. This law makes use of the just noticeable difference (JND), the least change in the physical stimulus that may be detected as difference. This was perhaps the first experimentally determined, quantitative measure of a mental event. Fechner extended the idea of Weber's law into a formula concerning the relationship between the increase of a stimulus magnitude and the growth of the experience of that magnitude. That logarithmic relationship would be called Fechner's law.

Fechner's work led directly to the methodology and psychophysical theory that would allow Wilhelm Wundt and other experimental psychologists to apply the experimental method to the study of experience.

References