Ken Giuffre, MD from John's Hopkins ~ quora.com/profile/Ken-Giuffre
I'm sorry but it's not psychic control or anything like that. The tremor in Parkinson's characteristically decreases its intensity and even disappears when the affected shaking extremity is called upon to make a purposeful movement. This is even one way your neurologist typically differentiates it from other types of tremors that get worse with purposeful movement, so-called 'intention tremors' as with alcohol intoxication. This is why a suspicious police officer on a DUI traffic stop will also perform that same maneuver wherein they have you touch your nose with your index finger, then reach for and touch it to their finger, back and forth as they reposition it to various points in front of your face. The Parkinson's tremor will decrease when you reach for their finger while the 'intention tremor' of inebriation and other causes like stroke will get worse as you reach and try to touch. That said, creating some purposeful internal awareness or construct will lessen or stop a Parkinson's tremor, but only as long as you are paying attention to it. For instance, one trick I do when the tremor in my right hand acts up is to reach my thumb across my palm to meet the pinky on the same hand. As long as I hold my hand in this 'purposeful' position, my tremor decreases significantly, that is, until I get distracted and forget. I hope this explanation has helped clear up your question.