Psychophysics is a term coined by Fechner to describe the interdisciplinary study of how humans perceive physical magnitudes.

The Weber–Fechner laws relate to human perception, more specifically the relation between the actual change in a physical stimulus and the perceived change. This includes stimuli to all senses: vision, hearing, taste, touch, and smell, but we should also include our “sixth sense”, PROPRIOCEPTION. So I’m going to focus on this particular sense and how these laws can help us to sharpen proprioception.

The Weber–Fechner law states that there is a constant proportion between a pre-existent stimulus and the minimum increase of that stimulus to produce a perceptible increase of sensation. That’s why it is called “Just noticeable difference”

Weber found that the just noticeable difference (JND) between two weights was approximately proportional to the weights.

I give you an example: Suppose that you are holding a weight of 100 g with your hand. Perhaps you can not perceive the difference from another weight of 105 g, but you can distinguish it from that of 110 g. So the JND (or differential threshold) is 10 g. If the mass is doubled, the differential threshold also doubles to 20 g, so that 220 g can be distinguished from 200 g. In this example, a weight (any weight) seems to have to increase by 10 % for someone to be able to reliably detect the increase.

This means that as higher the magnitude or intensity of stimulus, as higher the necessary increase to perceive the difference of sensation; or, by the contrary, as long as the pre-existent stimulus decreases, the necessary change to perceive the difference decreases as well.

Based on this, Feldenkrais came to the conclusion that the fact of reducing the muscle effort improves the sharpness of kinesthetic sensations and allows individual having a more accurate perception of what he or she is doing and becoming more aware of their movements.

I have transferred this concept to focal dystonia retraining getting excellent outcomes.