Quote Originally Posted by ChibiKeba
I'd like to think that a person's personality is based on many different factors and not just biology. On top of genetics and brain chemistry I think environment and experiences come into play. I know alot of people don't get into this aspect as much but I think the soul or the spiritual will power would have a heavy influence on personality type as well but as there's no way to really prove that I guess it's a moot point.
If you subscribe to Freud at all, babies have only an id, the ego/superego develops in order to repress the id (as the baby learns that the world does not revolve around them and their primal impulses and desires, etc. etc.).

So I guess environment has something to do with it, as far as that theory goes (maybe the point to which the id is repressed or the strength of their conscious functions, something like that).