I use IM signals quite a lot with my clients, whether via hand levitation, finger movement, nodding or other signal. It's usually quite easy to tell the difference between conscious and unconscious movements - the conscious movements tend to be quicker, and smoother (as Roger said), and altogether more deliberate. The unconscious movements are much slower, happen in tiny, sometimes jerky steps. This makes sense, I think. Each muscle which is involved in the movement is receiving its signal in turn and responding before the next one comes in. In conscious movement, the flow of signals is steadier. Although, come to think of it, I'm sitting here typing and I certainly wouldn't say that the movement my fingers are making is at all conscious - in fact, if i stop to think about it, I start making typos! So there is a distinction between a movement which is unconscious because it is so well learned that it can operate in the background, and an unconscious movement which is NOT learned, and is being directed from the unconscious (whater THAT is!).
I love Erickson and Rossi both - inspiring stuff!