I have learned many things this last year.
1. The host is simply another alter.
2. The host alter might, change and you or they never notice. At least for me, it's as if the hosts are all sharing one part of the brain. Lately we have had a new host almost daily - which we can do because there are hundreds of us. The Observing EP in charge of this sort of thing likes to experiment. When I was a young child, many hosts could remember being inside when they were host, others could not. So far in our experiment we have not found anyone that can come out and be the host, now that I am an adult, and remember the inside world. The memory of the inside world comes back to an alter as soon as that alter is no longer the host.
3. Some alters inside can see an hear many of the alters, but others can only see and hear a few. This was the case even in the earliest days of childhood. The alters that were often the host were all in a subgroup. If an alter from another subgroup (I have many subgroups) was host, then often the alters in the subgroup, that were usually the hosts, had total amnesia of the event.
As for scientific data to back this up --- I have not looked yet, because I am still experimenting.
Thoughts?