I would say that we dont need to prove the viability of shared dreams that the process of how and why is already out there the studies are just across different disciplines and in thousands of studies. I have been in the research stage for a documentary film on this very subject. the reason is genetic natural selection, the how is through bioelectromagnetic fields that we emit and hundreds of studies show this already. nrem states are generally for your daily grind while rem states are usually fear based and are designed for survival which depending on the type and severity will mark you genetically to be handed down to help the species survive. I personally believe the basis of animals in dreams is how we are helping each other to propel all of our species genetically though there is no study i have ever read regarding that.