Recently we had an interesting discussion about a scientific explanation of shared dreaming: https://community.ld4all.com/t/shared-dreaming/9964
We didn’t really come to a conclusion, but we felt it has something to do with converging brainwaves. Kinda like when you throw two stones in a pond. After some time, the resulting waves of both rocks collide and you get interference: the waves can strengthen each other or they can cancel each other out. This way I think a shared dream might be a collision between two brainwaves which were accidently focussed on each other (same wave energy and such). This analogy would implicate that a shared dream can be recognized fairly easy, because of the interfering waves of the other dream. Both dreams could melt together to some sort of a mixture which then opens the gate to explore each other dreamscapes.