The basic psychophysical law is associated with the name of Gustav Theodor Fechner (1801-1887), a German physicist, psychologist and philosopher, the founder of psychophysics. In his work "Elements of Psychophysics" (1860), he puts forward the idea that science needs a new field of knowledge that studies the patterns of correlation between physical and mental phenomena. This idea subsequently had a great influence on the development of experiment in psychology. Research in the field of sensations allowed Fechner to substantiate his well-known psychophysical Weber-Fechner law.
The foundations of the law are associated with the experiments of Ernst Heinrich Weber (1795-1878), a German anatomist, physiologist, founder of scientific psychology, along with such scientists as W. Wundt, G. Ebbinghaus and others. Weber owns the idea of measurement in psychological science.
First studies
The beginning that determined the Weber-Fechner law,E. Weber's research began in the field of visual and auditory sensations, as well as in the field of skin sensitivity (touch). In particular, Weber owns experiments with the body's temperature sensitivity.
So, for example, the effect of the so-called temperature adaptation was discovered. When one hand is first placed in cool water and the other in hot water, then warm water for the first hand will seem warmer than for the second, unadapted.
Types of skin sensations according to Weber
In 1834, Weber formulates his ideas about skin sensations ("On Touch"). The scientist identifies three types of these sensations:
- feeling pressure (touch);
- feeling temperature;
- sensation of localization (spatial location of the stimulus).
Weber owns the development of the esthesiometer (Weber's compass). Using this device, it was possible to estimate a sufficient distance to distinguish between two simultaneous touches to the surface of the skin of the subject. The researcher found that the value of this distance is not constant, its value for different parts of the skin is different. Thus, Weber defines the so-called circles of sensation. The idea that human skin has different sensitivities also influenced the Weber-Fechner law.
Formulation
The basis that determined the psychophysical law was Weber's research in the field of the correlation of sensations and stimuli (1834). It was found thatin order for a new stimulus to be perceived as different from the previous one, it must differ from the original stimulus by a certain amount. This value is a constant proportion of the original stimulus. Thus, the following formula was derived:
DJ / J=K, where J is the original stimulus, DJ is the difference between the new stimulus and the original stimulus, and K is a constant depending on the type of receptor being exposed. For example, to distinguish light stimuli, the proportion is 1/100, for sound stimuli - 1/10, and to distinguish weight - 1/30.
![Weber Fechner's law formulation [1]](https://i.vogueindustry.com/images/055/image-162946-4-j.webp "Weber Fechner's law formulation [1]")
Subsequently, on the basis of these experiments, G. Fechner determines the basic formula of the psychophysical law: the magnitude of the change in sensation is proportional to the magnitude of the logarithm of the stimulus. Thus, the relationship between the intensity of sensation and the strength of the stimulus, to which the Weber-Fechner law is directed, is expressed as follows: the magnitude of the intensity of sensations changes in an arithmetic progression, while the magnitude of the intensity of the corresponding stimuli changes in a geometric progression.
Limited law
Despite the objectivity of research, the psychophysical law of Weber - Fechner has a certain conventionality. It was found that subtle sensations are not constants. So, for example, it cannot be argued that a barely perceptible difference in sensations when exposed to loads of 100 g and 110 g is similar to a barely noticeable sensation when exposed toloads in 1000 g and 1100 g. Accordingly, the Weber-Fechner law is characterized by a relative value, first of all, for stimuli of medium intensity. In turn, within these limits, the law has serious practical significance.
