What are "Displaced Impulses?"
These are impulses that end up in the wrong part of body when a player is struggling with a passage technically and work contrary to the natural movements of the body. A classic example is someone bobbing their head when playing a difficult passage. Of course it can be any part of the body, but always prevents the natural motion needed to play a passage.
It often is easy to fix and can make things easier immediately. Follow these points and it should do the trick.
1. You must first notice that you are displacing an impulse. So sit in front of mirror and play a challenging passage and try to notice if you are unconsciously moving or tensing in the head, arms, shoulders, hands, face, jaw, legs, back and so on.
2. Once you notice these movements, play the passage in front of a mirror and consciously feel the motions being initiated in the fingers and avoid any extraneous movement. It should feel easier.
3. If you aren't able to stop the "displaced motions" then play the passage standing upuntil you are able to feel the movements initiated in the fingers and there are no extraneous motions.
That's it. Remember you are not trying to play like a statue. It is fine to have other bodily movements as long as they are responsive to your musical feelings. In other words if you feel the impulses initiated in the fingers and are simply following your musical voice, then any responsive movements are fine and won't interfere technically.
Once you have mastered feeling everything in the fingers and are following your musical impulses, the body will naturally do the correct movements.
Dounis apparently jumped on any student who was displacing impulses. So obviously this was an important point for Dounis and an unconscious pattern for many players.