What was Fechner’s insight on October 22, 1850? How did Fechner measure sensations?
On 22 October 1850, Fechner had an insight about the quantitative relationship, between mind and body. He said that the sensation and the material stimulus can be measured. He measured sensation by the change in the stimulus.
A sensation can be measured if, the change in the stimulus can be measured. He stated that stimulus does not produce one to one increase in the intensity of the sensation. Instead it is a geometric increase for stimulus while arithmetic increase for sensation.
He said that amount of sensation can be measured if the change in stimulus is also measured. One could formulate a numerical equation, which related to the sensation and stimulus. Now after determining what to measure Fechner devised a way to measure.
Fechner proposed two methods to measure sensations. Absolute threshold is one of the methods, by which one can determine whether stimulus is present or absent, sensed or not sensed. One could also measure the intensity of the stimulus at which subjects report that the sensation first occurred.
This is a useful tool but it has a limitation. Only, the lowest value of the sensation can be determined. To rectify this error he proposed another concept of differential threshold of sensitivity. This is defined as the least amount of stimulus given, that gives a change in the sensation. It tells, by how much must a weight be increased or decreased before the subject will report a noticeable difference in sensation.