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The Weber–Fechner law in musician’s focal dystonia retraining

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.

This is a pretty common question, which is often asked by many people who are going through this recovery process from musician’s focal dystonia, including some of my students.

Recently, rereading one of the splendid books by Feldenkrais, I came across this paragraph that answers, in part, this question:

“It must be fully realized from the start that the learning process is irregular and consists of steps, and that there will be downs as well as ups. This applies even to a matter as simple as learning a poem by heart.

A man may learn a poem one day, and remember almost nothing of it the next. A few days later, and without any further study, he may suddenly know it perfectly. Even if he puts the poem entirely out of his mind for several months, he will find that a brief rehearsal will bring it back completely. 

We must not become discouraged, therefore, if we find we have slipped back to the original condition at any time; these regressions will become rarer and return to the improved condition easier as the learning process continues.”

We must not forget that the fact of retraining our movements, in order to recover from focal dystonia, is still a relearning process. However, there are also other conditioning factors, such as the emotional factor, so that sometimes things turn out very well and others less well.

I would also like to emphasize the importance of considering the moments in which everything flows more easily, as a REGULAR situation and the other moments in which things do not go so well, as an EXCEPTIONAL situation and NOT THE REVERSE.

Thinking in this way, psychologically, has a very great positive impact in our mind and contributes to strengthening our confidence, determination and conviction that we are on the right track and are walking unfailingly towards our TOTAL recovery.