What Differentiates Lucid From Non Lucid Dreaming?

Some people do define dreams as a kind of a, a subspecies of hallucinations. And even in humans, we know that there are very different greas of lucidity. But it is a really interesting thought experiment to consider how one might go about that. One other possibility for going about that would be to look for the activation of executive centres in the brain in the middle of dreaming.