I wish the researchers well- it is a complex question.

I have lots of questions about dreaming. There is one I have never heard mentioned: There are frequent times when I am not aware that I have drifted off very briefly- actually just a few breaths' worth. I come back, suddenly aware that I must have dreamt a thought or conversation, because it never happened.

In the article it mentions that they/we now know that dreaming does not occur ONLY in REM sleep- that instant of sleep I mentioned should have told them that long since.