Three different states; we know they are different; but why?

What is the fundamental difference between the three states?

Is it awareness?
Self awareness?
The ability to think?
The ability to choose?
The knowledge of your senses?
The ability to make goals?
The ability to remember past events?
The knowedge that there is a past, present and future?

I realise that, in reality, it's probably very complex. However, I'm looking for a very simple core behaviour or action that separates these three states. I am hoping that it is one simple action/behaviour that exists to a small degree in non-lucid dreams, to a greater degree in lucid dreams, and to a great degree in the waking state. That way, ideally, you'd be able to identify occurrences of that behaviour in your non-lucids, increase the frequency of that behaviour in dreams (and in real life to condition yourself) until your non-lucids become lucid.