One of the most important parts important part of psychology is functional analysis between physical stimuli and effector or open (internal) responses, which has led to the establishment of psychophysical laws. The study of publicly observable stimuli and responses has allowed us to understand sensorimotor conditioning. But one may also be interested in knowing how external stimuli produce internal responses, which would be subjective experiences only accessible through introspective processesthis is the case of sensations.
Fechner, starting from Weber’s Law, attempted to measure sensory experience not by reference to physical measurements but through the djp of the differential threshold. Thus, through the accumulation of djp, the psychic continuum could be measured and related to the physical continuum, which is why he postulated the equality of the djp to be able to use them as a standard of measurement.
He set out to develop his law of:
- a principle: Weber’s law;
- a postulate: the equality of justly perceptible differences.
The statement of the law is: “the intensity of the sensation is proportional to the logarithm of the intensity of the stimulus.”
The mathematical formulation of his law is:
S = K logeE + C = Fechner’s law
With this formulation, Fechner defends that when the intensity of the stimulus grows according to a geometric progression, the sensation grows according to an arithmetic progression.
Three qualifications must be made to your law:
- It measures sensoriality indirectly since it allows a measurement of the sensation only by referring to the accumulation of djp to the physical magnitudes of the stimulus (for this reason, these scales are called cumulative or confusion, that is, they do not express units of measurement of subjectivity).
- Their measurements correspond to an interval scale and not to a ratio scale, so the transformation operations that can be carried out with the law are limited.
- The equality of the “djp” has finally been rejected by modern psychophysics, since they are proportional to the magnitude of the stimuli.
Modern psychophysics establishes two criticisms:
- the last point above
- The law only holds for intermediate values, as was the case with Weber’s law.
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