It’s impossible to tickle yourself – try! This is probably due to a cognitive phenomenon, called “efference copy” or “corollary discharge”. Initially, it covers the fact that, when performing an action, our nervous system sends messages to the senses influenced by it and makes them respond in a different way than usual. For example, this is one of the reasons why we do not experience the world turning when we turn our heads. The phenomenon also applies to the auditory system: Neural activity in the areas responsible for hearing is diminished when a sound occurs because of our own activity, as opposed to when it comes from other sources.
If it were truly impossible to sense the full effect of your own actions, it would be extremely bad news for musicians: then we would only be able to fully comprehend our sound quality or be able to evaluate the aesthetic content of our playing by listening to recordings of ourselves. Fortunately, it’s not impossible to listen “clearly” to yourself while playing – it’s just quite difficult. Speaking for myself, I have with this project become better at switching my focus to being “listening” instead of just “acting”, for example by deliberately closing my eyes or looking away from the music and the piano.
One of the hard steps to take as a performing musician is to be in an aesthetically experiencing mode while performing the music, but on rare occasions we actually succeed in being emotionally moved by our own musical performance (although it is not something we usually talk about much).
When I see myself practising, it is striking how much good phrasing, good sound-control, free movements in the body depend on being able to alternate between being “listening” and “acting”. Playing much more with closed eyes, as mentioned earlier, facilitates both these aspects. (See About being in several places at the same time). Visual feedback is not optimal either to “feel” or “listen” because the visual system focuses on the location of fingers, on the outer shape of the movements and on the notes. (In parentheses, however, it may be beneficial to focus visually on elements close to the acoustic tone production, for example, to look at the movements of the dampers inside the piano. It facilitates focus on the end result, namely the hammer’s attack on the string and the resulting sound).
The result is often a holistic sensation: I imagine / move / experience as a connected phenomenon, and it is also by this experience that the good and artistically communicating performance presents itself. If I find it difficult to find this feeling, it is beneficial for me to be aware of both my inner sensation of muscular relaxation and on the aesthetic result – the sound and the phrasing (See About muscular tension and movements).
It is also a powerful educational tool if the students can learn to be better at directing their attention towards listening. When they focus on “tickling themselves”, they often develop much faster than simply repeating motoric practice methods. But it requires a very specific awareness of how to change attention. The good news is that this awareness may certainly be trained, and I hope that my project can help present new directions here. (See About recording yourself).
Moreover, there is another interesting thing about the cognitive phenomenon that sensations that depend on our own actions have a special status: Presumably the responsibility for this effect is in the (posterior) parietal cortex and if this region has hyperactivity, either due to illness or external electrical stimulation, one will get problems with self-identification or even have out-of-body experiences. This can be explained by the fact that we no longer experience the consequences of our actions as coming from ourselves. So the very connection between intention, execution and sensation of our actions is obviously central to us.
 Marc Jeannerod: Motor Cognition: What actions tell the self. Oxford University Press 2006, 19
 Marc Jeannerod: Motor Cognition: What actions tell the self. Oxford University Press 2006, 83