This article is from the Dissociation FAQ, by Discord (firstname.lastname@example.org) with numerous contributions by others.
When several alters are out at once, they may talk at the same time,
causing incredibly garbled sentences to emerge. Or they may listen at
the same time, causing, for example, each of two alters to catch every
other word in a sentence. When this happens, neither of them will
understand what was said.
Additionally, switches may cause disorientation, even within multiples
that are co-conscious to some degree.
For multiple systems that are particularly integrated/co-conscious, it may
be difficult to have a sense of self at times. It is possible to not be
sure who was "doing", and who was just watching. This seems to be
exacerbated with greater similarity between alters.
People who are dissociative but not multiple probably find themselves
with similar feelings to those who are somewhat integrated/co-conscious.