Yes, Thomas, I think I should not have chosen the word 'correlative' because it does not contain the exact meaning I search for.  I would say a relationship does exist between this ability to attend and physiology- yet as the violin does not create the music, however it fundamentally conditions it, I think the body (nervous system) has the same relationship to the capacity of attention.  I can, and should, say more about this, but have no time at this right now. Yes, correlative is wrong word here.  Gunthar