The Scientific Context
The Scientific Context
The emerging natural sciences of the eighteenth and nineteenth centuries became increasingly specialized as knowledge increased and as opportunities for specialized teaching and research came into being in the German universities (Ben-David, 1971).
The study of physiology emerged as a discipline separate from anatomy as the nineteenth century began. Studying intact physiological systems, in vivo or in vitro, accelerated the understanding of the functional characteristics of those systems and built on the knowledge gained from the study of anatomy via dissection.
The methods and subject matter of physiology, especially sensory physiology, helped to provide the scientific basis for psychology.Sensory Physiology Johannes Muller (1801–1858), the “Father of Physiology,” produced the classic systematic handbook 1833–1840) that set forth what was then known about human physiology and offered observations and hypotheses for further research. Among the formulations that Muller provided in the Handbook was the law of specific nerve energies, which stated that the mind is not directly aware of objects as such but can only be aware of the stimulation in the brain conveyed by sensory nerves.
The perceived qualities of stimulation depend upon the sense organ stimulated, the nerve that carries the excitation from the sense organ, and the part of the brain that receives the stimulation. Muller's pupil, Hermann von Helmholtz (1821–1894), extended the law of specific nerve energies by theorizing that qualities of stimuli within a sensory modality are encoded in the same way that they are encoded among modalities.
That is, distinguishing red from green, or a low pitch from a high one, depended upon specialized receptors in the eye or ear, distinct nerve connections within the visual or auditory system, and specific locations within the visual or auditory areas of the brain that receive the stimulation.
The testing of the theory depended upon an individual’s report of the sensory experience (“I see red”), the nature of the stimulus to which the individual responded (a specific wavelength of the energy spectrum), and knowledge of the physiological organization of the sensory systems.
Relating the experience to the stimulus was a matter of experimental research that could be carried out with intact human beings; detecting the activity of nerves and the location of the brain to which stimulation was transmitted was possible then only with in vitro preparations of animals.
Relating subjective, psychological experience to specific external stimulation was one step in suggesting how psychology might become a science. Psycho physics Experiments on the sense of touch were carried out by the physiologist E. H. Weber, who distinguished among the feelings of pressure, temperature, and the location of stimulation on the skin.
In conducting experiments in which he stimulated his own skin, Weber explored skin sensitivity and demonstrated that “on the tip of the forefinger and lips two fine compass points could be felt as two when they were less than one-twentieth of an inch apart, but if they were nearer they seemed to be one”.
Not only could touch sensitivity be measured at different points on the skin, but relative sensitivity at a single point could also be measured. Placing a standard weight at a given spot on the skin and then asking for a second weight to be judged “heavier” or “lighter” showed that the amount of weight that could be judged heavier or lighter than the standard varied as a proportion of the magnitude of the standard weight.
Thus, the minimal detectable difference between two weights was relative to the weights involved; for heavy weights, differences would have to be large, but smaller differences could be detected when the weights involved were light. G. T. Fechner (1801–1887), a physicist, saw in Weber’s results the possibility of relating mental events to physical events; subjective judgments about physical magnitudes could be compared to the actual physical magnitudes.
Fechner had believed since his student days “that the phenomena of mind and body run in parallel”. His solution to the problem of relating these two aspects of the world was to make “the relative increase of bodily energy the measure of the increase of the corresponding mental intensity”. Although Fechner conceived of the possibility independently of Weber’s results, he came to realize that his speculations about arithmetic and logarithmic relations between physical and subjective magnitudes were in fact demonstrated by Weber’s observations.
Weber’s results showed that sensory judgments of magnitude formed ratios that were sufficiently regular to assume the status of a law. Fechner designated as Weber’s law the mathematical equation that stated that the increase in perceived intensity of a stimulus (the “just noticeable difference”) was, as Weber had demonstrated, a constant proportion of the intensity of the stimulus to be increased.
The regularity in ratios across a wide range of intensities led Fechner to rewrite the law in terms of a logarithmic progression, with the strength of a sensation equal to the logarithm of the intensity of a stimulus multiplied by a constant established experimentally for the sensory system under study. “Weber’s law” now typically refers to the “simple statement that the just noticeable difference in a stimulus bears a constant ratio to the stimulus” while “Fechner’s law” typically refers to the logarithmic relationship that Fechner formulated.
Fechner called the new science that he established psycho-physics and developed laboratory procedures that became part of the laboratory experiments of the new psychology as well as of the physiological research on the special senses.
The measurements of the smallest detectable intensity (absolute threshold) and the smallest detectable difference in intensities between stimuli (difference threshold) for the different senses were pursued by the several methods that Fechner had devised for the purpose.
Resolving differences in results obtained for different methods, testing psycho physical laws over a wide range of stimulus intensities, and developing scales of psychological measurement offered significant research challenges for psychological laboratories well into the twentieth century.
The emerging natural sciences of the eighteenth and nineteenth centuries became increasingly specialized as knowledge increased and as opportunities for specialized teaching and research came into being in the German universities (Ben-David, 1971).
The study of physiology emerged as a discipline separate from anatomy as the nineteenth century began. Studying intact physiological systems, in vivo or in vitro, accelerated the understanding of the functional characteristics of those systems and built on the knowledge gained from the study of anatomy via dissection.
The methods and subject matter of physiology, especially sensory physiology, helped to provide the scientific basis for psychology.Sensory Physiology Johannes Muller (1801–1858), the “Father of Physiology,” produced the classic systematic handbook 1833–1840) that set forth what was then known about human physiology and offered observations and hypotheses for further research. Among the formulations that Muller provided in the Handbook was the law of specific nerve energies, which stated that the mind is not directly aware of objects as such but can only be aware of the stimulation in the brain conveyed by sensory nerves.
The perceived qualities of stimulation depend upon the sense organ stimulated, the nerve that carries the excitation from the sense organ, and the part of the brain that receives the stimulation. Muller's pupil, Hermann von Helmholtz (1821–1894), extended the law of specific nerve energies by theorizing that qualities of stimuli within a sensory modality are encoded in the same way that they are encoded among modalities.
That is, distinguishing red from green, or a low pitch from a high one, depended upon specialized receptors in the eye or ear, distinct nerve connections within the visual or auditory system, and specific locations within the visual or auditory areas of the brain that receive the stimulation.
The testing of the theory depended upon an individual’s report of the sensory experience (“I see red”), the nature of the stimulus to which the individual responded (a specific wavelength of the energy spectrum), and knowledge of the physiological organization of the sensory systems.
Relating the experience to the stimulus was a matter of experimental research that could be carried out with intact human beings; detecting the activity of nerves and the location of the brain to which stimulation was transmitted was possible then only with in vitro preparations of animals.
Relating subjective, psychological experience to specific external stimulation was one step in suggesting how psychology might become a science. Psycho physics Experiments on the sense of touch were carried out by the physiologist E. H. Weber, who distinguished among the feelings of pressure, temperature, and the location of stimulation on the skin.
In conducting experiments in which he stimulated his own skin, Weber explored skin sensitivity and demonstrated that “on the tip of the forefinger and lips two fine compass points could be felt as two when they were less than one-twentieth of an inch apart, but if they were nearer they seemed to be one”.
Not only could touch sensitivity be measured at different points on the skin, but relative sensitivity at a single point could also be measured. Placing a standard weight at a given spot on the skin and then asking for a second weight to be judged “heavier” or “lighter” showed that the amount of weight that could be judged heavier or lighter than the standard varied as a proportion of the magnitude of the standard weight.
Thus, the minimal detectable difference between two weights was relative to the weights involved; for heavy weights, differences would have to be large, but smaller differences could be detected when the weights involved were light. G. T. Fechner (1801–1887), a physicist, saw in Weber’s results the possibility of relating mental events to physical events; subjective judgments about physical magnitudes could be compared to the actual physical magnitudes.
Fechner had believed since his student days “that the phenomena of mind and body run in parallel”. His solution to the problem of relating these two aspects of the world was to make “the relative increase of bodily energy the measure of the increase of the corresponding mental intensity”. Although Fechner conceived of the possibility independently of Weber’s results, he came to realize that his speculations about arithmetic and logarithmic relations between physical and subjective magnitudes were in fact demonstrated by Weber’s observations.
Weber’s results showed that sensory judgments of magnitude formed ratios that were sufficiently regular to assume the status of a law. Fechner designated as Weber’s law the mathematical equation that stated that the increase in perceived intensity of a stimulus (the “just noticeable difference”) was, as Weber had demonstrated, a constant proportion of the intensity of the stimulus to be increased.
The regularity in ratios across a wide range of intensities led Fechner to rewrite the law in terms of a logarithmic progression, with the strength of a sensation equal to the logarithm of the intensity of a stimulus multiplied by a constant established experimentally for the sensory system under study. “Weber’s law” now typically refers to the “simple statement that the just noticeable difference in a stimulus bears a constant ratio to the stimulus” while “Fechner’s law” typically refers to the logarithmic relationship that Fechner formulated.
Fechner called the new science that he established psycho-physics and developed laboratory procedures that became part of the laboratory experiments of the new psychology as well as of the physiological research on the special senses.
The measurements of the smallest detectable intensity (absolute threshold) and the smallest detectable difference in intensities between stimuli (difference threshold) for the different senses were pursued by the several methods that Fechner had devised for the purpose.
Resolving differences in results obtained for different methods, testing psycho physical laws over a wide range of stimulus intensities, and developing scales of psychological measurement offered significant research challenges for psychological laboratories well into the twentieth century.
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