Existentialists believe that we all arrive on earth as a blank slate, essentially, and we become by existing. Therefore, all attributes are extrinsic. I bought into this idea, for the most part, after learning about it in my philosophy courses at school and considering the impact of it in my own life. I made sense of it in the context of my personal religious beliefs as well, although I didn't take it to be necessarily true (as a philosophy student I question everything and take very little to be unquestionably/necessarily true).
Since having Squeaker I believe that I have even more reason to question the necessary truthfulness of this philosophical concept. She seems to have attributes, both characteristics of personality and of physical capabilities, that I neither taught her nor think that she picked up from observing others around her. For instance, why is it that Squeaker naturally started to push herself up onto her knees without seeing anyone else do that? Are people born with the tendency or capability to do this and simply end up doing it without outside help? Squeaker also seems to find some things humorous without the help of us laughing at it first or trying to make it funny. Is this just part of some kind of wired personality? Perhaps I am taking for granted the human mind (and body), as well as what it is capable of, even at an early age and during the susceptible time of life that is infancy.
It is possible that babies push themselves up to their knees because they see how their parents move and this is the first capable step they can make towards doing that. It could still be a learned step towards gaining an independent perspective, becoming mobile on one's own. Maybe the desire to emulate one's parents is innate then and the very act of trying to be independent is something we are all born with? Squeaker might observe the world and the reaction she has learned from us is the act of laughing or smiling, whether she actually finds something humorous is questionable. However, crying and sucking are things that we surely do not teach our children, are they then innate skills? They could simply be explained by existentialists as being initial reactions, coping mechanisms that are learned and reinforced within the womb and the moments after birth. Babies learn to suck and obtain nutrients or comfort this way within the womb. Crying might just be a knee-jerk reaction to a shocking experience, then it turns out to be the only way they can learn to communicate with us in those first months of life.
It is quite possible that I am simply arguing for both sides to the same coin and both innate and extrinsic features form the base for our attributes. Perhaps we cannot have one without the other. None of the things I have said here are yet well-researched or examples of how I would truly argue this out in a published work, they are simply meanderings of my mind and observations.
I am interested in your thoughts and perspectives on this subject though. Do we learn to be ourselves, is there a certain "me-ness" and "you-ness" that each of us is born with or is it both? Do we all naturally know how to become independent creatures, taking steps to do that with or without parental guidance, or are we all learning to be independent by observing others? We'll probably never know for sure, and that is the beauty of philosophy.