humans have many different states of awareness and perception:
awake, focused, day dreaming, “lost in thoughts”, sleepy, sleep, dream, LD (Lucid dreams), OBE (Out of Body Experience), RV (Remote Viewing)…
Some of these states have been studied and are fairly well known: observed under laboratory conditions, specific brain patterns, heart rates, metabolism, obviously repeatable (awake, sleep, dream),…
Some are more difficult to reproduce and do not seem to be as universal such as Lucid Dreaming which have been studied and demonstrated as an existing mode of awareness.
The first verified communication between a dreamer (REM sleep) and an outside observer was established by Keith Hearn at Hull University, England in 1975. Later Stephen Laberge (Stanford University then The Lucidity Institute) developed LD inducing techniques such as the MILD (Mnemonic Induction of Lucid Dreams). You can do a web search for this or/and get Laberge’s original book: Exploring The world of Lucid Dreaming.
The issue is that many people do have (or do not remember?) some of these states (LD, OBE,…), others have few or/and tenuous memories of them.
For these states to be studied and proven real, one of the first step is to be able to generate them and repeat them at will or close to it. This is where the problem is: they might not happen for weeks then suddenly happen when you expect them the least. I never met anyone who can produce them on command. (Maybe there are people who can? And if they do(?), they might not be interested in demonstrating anything to anyone?)
Of course the fact that anyone (me included) claims we had an OBE, does not mean OBEs are real. It only means that we had some experience where our brain was convinced that we were existing, awake, aware and outside of our physical body. The fact we are convinced of the reality of these states does not mean they are real. It simply means our brain believed it while it was happening. The fortunate thing is that because you believe something does not mean it is real: you can be deceived, your brain can make it up, you can be delusional,… only by repeating this state under strict laboratory experiments could you demonstrate they are real. And this has not been done.
For more info and to see why I think they are real, see one of my previous post here:
Dan Frayssinet’s answer to Does Astral projection play a role in the brain or is it an out of body experience where you have your soul but leave your body behind?
This answer originally appeared on this Quora question on Astral Projection.