As first I want to say that these are only my personal thoughts and many of you probably won't agree, so please don't be harsh on me. ;)

I personally think that when soul is placed to new physical body to start new incarnation, in that moment soul should connect with body fully, that means should starting identify as that physical creature that soul will be for this specific incarnation, soul shouldn't be aware of being soul while have physical form, it's for soul to fully experience that incarnation and don't remember what was before etc. But sometimes that connection isn't full, I don't know why, maybe because humans are too far from nature since soo long ago, I don't know if such problems are existing for other physical creatures, if they can identify as something else instead of that specific creature which body they have, so I can't tell... But I think, while connection with human body isn't full, soul, as shouldn't be aware of being soul, automatically and unconsciously is choosing another identity, sometimes it's creature from their previous incarnation, sometimes something that specific soul likes and is important to it, that feels connection with, and in some cases there are created multiple identities when soul unconsciously choosing many creatures and things that feels connection with, but every of those identities are part of that specific soul, so every identity is very important and is connected with that soul's personality. And in I think really rare cases, soul is still aware of being soul, even if is in physical incarnation, I think it's rare, because I've met only one other soul besides me, so...