Ernst Weber

8 Key excerpts on "Ernst Weber"

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  A History of Modern Psychology

  • C. James Goodwin(Author)
  • 2022(Publication Date)
  • Wiley

    (Publisher)

  Science demands objective measurement, and threshold research fit the bill. Second, Weber showed that there was not a one-to-one relationship between changes in the physical world and the psychological experience of those changes. Increasing a weight by 3 grams does not always produce the same experience; sometimes differences are perceived (if S = 30), sometimes not (if S = 60). Consequently, understanding how the mind organizes its experiences requires knowing more than just the physical dimensions of the stimuli we are exposed to; it also requires an attempt to determine how the mind interprets those physical stimuli. Third, Weber’s law showed that mental and physical events could be related mathematically. That insight would be developed more fully by another Leipzig scientist. Gustav Fechner (1801–1889) Weber’s goal as a physiologist was to understand the tactile and muscle senses, and to do so he used methods that would eventually be known as psychophysical. His younger Leipzig colleague Gustav Fechner had an even more ambitious goal, however. Fechner was obsessed with the idea of resolving the ageless mind–body problem in a way that would defeat materialism, which he considered nothing short of evil, and he thought that psychophysics was the way to do it. A case can be made for calling Fechner the first experimental psychologist, even though he was trained as a physician, made his repu- tation as a physicist and, when he was in the midst of his pioneering research in psychophysics, thought of himself as a philosopher. Fechner was born in a Lutheran parsonage in southern Germany in 1801; he was a precocious child, familiar with Latin by age 5, for example. At 16 he entered the University of Leipzig to study medicine, and his education included a dose of physiology with Weber. Though Fechner earned an MD in 1822, he never practiced medicine.

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  Essentials of Sensation and Perception

  • George Mather(Author)
  • 2014(Publication Date)
  • Routledge

    (Publisher)

  Starting from the initial detection of a very weak stimulus (a tiny weight, a dim light), he reasoned that if you were to count up just noticeable differences in stimulus intensity you would actually be counting up equal sensory intervals along a subjective, psychological scale of perceived magnitude. So a small increment to a light weight (or a dim light, or a quiet sound) would produce the same increase in perceived weightiness (or brightness or loudness) as a large increment to a very heavy weight (or a bright light, or a loud sound). This insight became known as Fechner’s Law, and it had a fundamental impact on psychology and physiology. It offered the beginnings of an answer to an age-old philosophical problem, the relation between mind and body, the mental (psychical) world and the physical world. Fechner had discovered a simple mathematical link between the laws of the mind and the laws of physics; a psychophysical law. He went on to work out and formalize a set of psychophysical methods for measuring JNDs. Variants of these methods are still in use today to measure both JNDs and other more complex psychophysical phenomena, and they still yield insights about sensory function that could not be obtained by any other means. Key Term Fechner’s Law. A principle describing the relationship between sensation magnitude and stimulus magnitude. Key Concept Psychophysical threshold In Elemente der Psychophysik, published in 1860, Fechner described several experimental methods to measure the relation between sensory stimuli and perceptual responses, and these methods have been refined over the years to improve their reliability. As an example, consider a simple ‘yes/no’ psychophysical method to measure the relation between stimulus intensity and detection. The participant is presented with a stimulus, and asked to respond ‘yes’ or ‘no’ to indicate whether they can detect it or not

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  An Historical Introduction To Modern Psychology

  • Gardner Murphy, Murphy, Gardner(Authors)
  • 2013(Publication Date)
  • Routledge

    (Publisher)

  2 who was working in the field of acoustics, had hit upon the fact that if a wire of a certain length and tension was struck, and its pitch compared with that of a similar but slightly longer wire, a constant difference in the length of the wires was necessary to make possible a correct pitch-discrimination. He worked with 240 vibrations per second as a standard, and found how much higher the pitch of the second tone had to be in order to enable the subject to distinguish it from the standard. Weber seized upon this observation as another instance of his law. But, as Delezenne had used only one standard, Weber was mistaken in utilizing this conclusion in support of his own. From the results of all the experiments noted, Weber believed that his general principle was founded on facts from the skin, muscle, eye, and ear.

  2 Recueil des travaux de la société des sciences de Lille (1826).

  It would be hard to over-emphasize Weber's importance in the genesis of an experimental psychology. His interest in physiological experimentation served to turn the attention of physiologists to the legitimacy and importance of approaching in the laboratory certain genuinely psychological problems which had throughout history been neglected. Not only did he set problems which occupied men of the ability of Helmholtz, Fechner, and Lotze, but he himself attacked a great many of these problems, and pointed the way to their systematic study.

  An illustration will show the extent to which he could transform the problems of the physicist and the physiologist. An experiment had been carried out in France (by Bouguer) a generation before Weber's time, in which the sensitiveness of the eye to light was measured by varying the relative positions of candles and pinholes through which light reached a screen beyond. In order to make a faint shadow dis tinguishable from a shadowed area adjacent to it, it was found that the illumination of the two must differ by one sixty-fourth. The problem led to no principle of any par ticular consequence. Yet it was in embryo the problem of "just noticeable differences." It was just such a problem as in the hands of a Weber might have become a corner-stone of epoch-making research.

  It is no accident that work like Weber's came when and where it did. German intellectual history for a century had paved the way; the influence of Haller still lived, enriched by the brilliant French discoveries of the late eighteenth century, which had been adopted with new energy by the German universities in the early years of the nineteenth century. Important as it may be to plant wisely the seed of an experimental project, the soil is no less important. When Hamilton, a few years later, undertook to study experimentally some problems in attention, nothing of significance resulted in British psychology; associationism and the Scottish school were alike uninterested. The crucial point was that in Germany experimental physiology was solidly established with quantitative methods and with a wide outlook. These many investigations conducted by Weber, such as the problem of the "just noticeable differences", were throughout envisaged in quantitative terms; and the last of these was experimental in the more restricted modern sense, several different factors being varied in order to isolate the significance of each. Weber ventured, moreover, to bring together an array of results under a common law, a universal principle. Important as this law was to become as a hypothesis for voluminous research, Weber's greatest significance lies rather in his conception of an experimental approach to psychological questions, and in the stimulation of research through which ultimately a vast variety of problems other than his have been inductively studied.

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  Hergenhahn's An Introduction to the History of Psychology

  • Tracy Henley(Author)
  • 2018(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  As the name suggests, psychophysics is the study of the relationship between physical and psycho-logical events. Fechner’s first step in studying this relationship was to state mathematically what Weber had found and to label the expression Weber’s law: D R R 5 k, where R = Reiz (the German word for “stimu-lus”). In Weber’s research, this was the standard stimulus. ∆R = The minimum change in R that could be detected; that is, the minimum change in physical stimulation necessary to cause a person to experience a jnd. k = A constant. As we have seen, Weber found this constant to be 1/40 of R for lifted weights. Weber’s law concerns the amount that a phys-ical stimulus must change before it results in the awareness of a difference or in a change of sensation ( S ). Through a series of mathematical calculations, Fechner arrived at his famous formula, which he believed showed the relationship between the men-tal and the physical (the mind and the body): S = k log R This formula mathematically states Fechner’s earlier insight. That is, for sensations to rise arith-metically (the left side of the equation), the magni-tude of the physical stimulus must rise geometrically (the right side of the equation). This means that as a stimulus gets larger, the magnitude of the change must become greater and greater if the change is to be detected. For example, if the stimulus ( R ) is 40 grams, a difference of only 1 gram can be detected; whereas if the stimulus is 200 grams, it takes a dif-ference of 5 grams to cause a jnd. In everyday terms, this means that sensations are always relative to the level of background stimulation. If a room is dark, for example, turning on a dim light will be imme-diately noticed, as would a whisper in a quiet room. If a room is already illuminated, however, the addi-tion of a dim light would go unnoticed, as would a whisper in a noisy room. However, Fechner did not believe his formula applied only to the evaluation of simple stimuli.

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  Sensation and Judgment

  Complementarity Theory of Psychophysics

  • John C. Baird(Author)
  • 2014(Publication Date)
  • Psychology Press

    (Publisher)

  After reviewing the empirical evidence on local psychophysics, an explanation of stimulus discrimination consistent with the traditional Fechnerian view, but built on the assumptions of the Sensory Aggregate Model, is proposed. The source of internal variability is ascribed to the firing rates of neurons comprising the ensemble of excitation associated with each stimulus. The standard deviation of this firing rate distribution is the sensory correlate of the JND obtained psychophysically.

  WEBER’S LAW

  The oldest way to determine perceptual sensitivity is to ask what minimum stimulus change is necessary for a subject to notice a difference. Using the approach introduced by Weber (1846) and Fechner (1860/1966), it was proposed in the last century that the JND is a linear function of the intensity at which it is determined. Weber’s law describes this empirical relation, where ΔS is the JND, S is the standard, and k is the Weber fraction.

  The value of k reflects the discriminability of closely spaced stimuli: the higher k, the lower the sensitivity. Table 4.1 lists typical Weber fractions for a variety of stimulus attributes. The values range from 0.02 for electric shock to 0.24 for odor. (These values are taken from empirical studies cited in Baird, 1970a, and Baird & Noma, 1978).

  TABLE 4.1Representative Weber Fractions (after Baird & Noma, 1978)

  Attribute	Weber FractionΔS/S
  Finger span	0.02
  Saturation (red)	0.02
  Electrical (skin)	0.03
  Position of point (visual)	0.03
  Length of lines (visual)	0.04
  Area (visual)	0.06
  Heaviness	0.07
  Brightness	0.08
  Loudness (1000 Hz, energy units)	0.10
  Taste (salt)	0.14
  Taste (sweet)	0.17
  Skin vibration (100 Hz–1100 Hz)	0.20
  Smell	0.24

  Figure 4.1

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  History of Modern Psychology

  A Global Perspective

  • C. James Goodwin(Author)
  • 2023(Publication Date)
  • Wiley

    (Publisher)

  Idea strength can change, however, through such factors as fatigue or distraction. Thus, the fact that I mentioned the upcoming weekend twice in the last paragraph, combined with the possibility that you have been reading for a while and are tiring of it, thoughts of the weekend might strengthen, and your apperceptive mass might shift from Herbart to the prospect of a nice cold beer. For the purposes of this chapter, Herbart’s importance is that he began to think about psychology as a discipline that was separate from philosophy and that did not necessarily require an understanding of physiology. Boring (1950) eloquently summed up Herbart’s influence this way: “What Herbart gave to psychology was status. He took it out of both philosophy and physiology and sent it forth with a mission of its own” (p. 252). 1 One effect of this mission was the creation of techniques to examine the thresholds Herbart described, those separating events above and below the apperceptive mass. Ernst Weber (1795–1878) Weber spent most of his academic career at the University of Leipzig, first as a student and then as a professor of anatomy and physiology from 1821 until his retirement in 1871. In the 1820s physiologists were beginning to learn a great deal about vision and hearing, but little was known of the other senses. Weber set out to correct the imbalance by becoming the leading authority on the tactile senses (Dorn, 1972). He made two major contributions: mapping the relative sensitivity of various locations on the skin, and demonstrating a mathematical relationship between the psychological and the physical that would establish psychophysics and later be known as Weber’s law. Two-Point Thresholds To examine tactile sensitivity, Weber used a technique in which he touched the skin’s surface with a simple device resembling a two-point drawing compass.

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  A History of Modern Psychology

  • Per Saugstad(Author)
  • 2018(Publication Date)
  • Cambridge University Press

    (Publisher)

  He found that the increase needed to produce an impres- sion of change is approximately proportional to the physical value of the stimulus. Later researchers have referred to this finding as Weber’s law. Gustav Theodor Fechner (1802–1887) Gustav Theodor Fechner was trained as a medical doctor at the University of Leipzig, where Weber was a teacher. Initially interested in physics, Fechner conducted studies of electricity that gained him a physics professorship. After some years, illness forced him to resign from his position, but after a decade in which he had not been able to do research, he returned with a very original project. In addition to being a well-trained scientist, accustomed to the use of measurements and quantitative treatment of data, Fechner was a philosopher who, in the manner of the earlier generation of Romantics, was convinced that mind and nature are one. It occurred to him that he could prove there is an identity between mind and nature by demonstrating that changes in sensory processes (which he saw as the mental aspect) correspond to the physical stimulation producing the sensory impression. He thus developed the concepts of differential threshold and absolute threshold. By differential threshold he meant the increase in physical stimulation needed to produce a change in the corresponding sensory impression; by absolute threshold he meant the smallest physical stimulation that could be detected. To accurately determine these thresholds, Fechner developed specific methods called psychophysical methods. The methods, which we need not describe here, aimed to arrive at reliable estimates by presenting the stimuli in prescribed ways and treating the responses in a quantitative manner. Fechner conducted his experiments with great thoroughness and was able to present a number of reliable threshold values.

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  Human Factors Engineering and Ergonomics

  A Systems Approach, Second Edition

  • Stephen J. Guastello(Author)
  • 2013(Publication Date)
  • CRC Press

    (Publisher)

  The notion of response probability was introduced a bit later in time when it became apparent that abso-lute thresholds were not so absolute; this issue is addressed by signal detection theory. Difference thresholds in the classical paradigm were obtained in a similar fashion, except that the human participants would be presented with a standard stimulus and a second stimulus. The minimum value of the second stimulus that would produce a response from the subject saying that the two stimuli are different is taken as the JND. Fundamental Laws Classical psychophysics produced two important laws. According to Weber’s law, the ratio of the change in intensity to initial intensity is a constant: Δ I / I = C or Δ I = CI (3.1) or alternatively, that change in perceived intensity is proportional to the initial intensity, where Δ I = JND, and I = initial intensity. C is constant for all values of a particular type of stimulus, such as loudness of a tone, brightness of a conventional lightbulb, and so forth. Not surprisingly, Weber’s work began with the perception of weights. It was not until elec-tric power became available, along with equipment to plug into it, that it was possible to deliver controlled stimuli of many other varieties. Fechner’s law was derived from Weber’s law. According to Fechner’s law, psychological signal strength is a logarithmic function of physical signal strength: Ψ s = k log( I ), (3.2) where Ψ s is the psychological magnitude, k is a constant, and I is physical magnitude. Once again, k is specific to the type of stimulus (d’Amato, 1973). A close variant of Equation 3.2 specifies that the sensation of a stimulus is relative to the absolute threshold, I ′ for the stimulus: Ψ s = k log( I / I ′ ). (3.3) Signal decreasing Signal increasing Signal strength Response probability FIGURE 3.1 Charting absolute thresholds in a classical psychophysics experiment.

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