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 laws of the relationship between physical and mental phenomena. This idea subsequently had a great influence on the development of the experiment in psychology. Research conducted in the field of sensations allowed Fechner to substantiate his well-known psychophysical law Weber - Fechner.
The foundations of the law are connected 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 has the idea of measurement in psychological science.
First research
The beginning that determined the law of Weber - Fechner was the research of E. Weber 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 temperature sensitivity of the organism.
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 after that warm water for the first hand will seem warmer than for the second, unadapted.
Types of skin sensations according to Weber
In 1834, Weber formulated his ideas regarding skin sensations ("About touch"). The scientist identifies three types of these sensations:
- feeling of pressure (touch);
- sensation of temperature;
- a sense of localization (spatial arrangement of the stimulus).
Weber owns the development of an esthesiometer (Weber compasses). Using this device, it was possible to evaluate a sufficient distance to distinguish between two simultaneous touches on 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.
Wording
The basis that determined the psychophysical law was Weber's research in the field of correlation of sensations and stimuli (1834). It was found that in order for a new stimulus to be perceived as different from the previous one, it must have a certain amount of difference from the initial stimulus. This value is a constant proportion of the original stimulus. Thus, the following formula was derived:
DJ / J = K,
where J is the initial stimulus, DJ is the difference between the new stimulus and the initial one, and K is a constant depending on the type of receptor exposed. For example, a ratio of 1/100 is needed to distinguish light stimuli, 1/10 for sound stimuli, and 1/30 to distinguish weight.
Subsequently, based on the data of 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 in the following: the magnitude of the intensity of sensations changes in arithmetic progression, while the magnitude of the intensity of the corresponding stimulations changes in geometric progression.
Limited law
Despite the objectivity of research, the Weber-Fechner psychophysical law has a certain conventionality. It was found that subtle sensations are not constant values. 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 to loads of 1000 g and 1100 g. Accordingly, the Weber – Fechner law is characterized by a relative value, first of all, for irritants of medium intensity. In turn, within these limits, the law has serious practical significance.