Nature or nurture

I think anyone that has a baby will tell you that it is astonishing how quickly they seem to learn things.  Lately I have been watching Sprog and been thinking a lot about nature versus nurture.  I am sure in the end it must be a balance of the two but I can't help to think that a lot of things must be, at least on a basic level, by instinct.  

I do try to expose him to new stimuli by involving him in my activities as much as possible.  He is never left behind: he is with me wherever I go and whatever I do and I try to show him as much of what I am doing as possible.  However, he cannot possibly understand why things are being done or what is being done yet.  In the first instance it must just be the urge to copy what he sees.  He has learnt, for example, that I like playing a game with him where I put our feet together, underside of my feet to his, and I nudge his legs in different directions.  He responds by trying to exert pressure himself and trying to push my feet in different directions.  One day he took the initiative to do it when one of my feet were close enough to his while he was sitting in his rocker.  This is good but something else happened the another day some time after this incident. I held my hand in front of his face and wiggled my fingers while he was lying on the changing mat.  The response from him was to put his palm against mine and try to play 'footsie' with our hands.  To check if that was just an accident, I put my other hand up and he tried to play with his other hand as well.  Seeing as I have never done that with him before, this must be something that has come completely from him.  

Another related game he now plays is to kick my hand if I place it near his feet; if he gets the sole of his feet on the palm of my hand, he will play footsie with it.  Whatever height I place my hand at, he will try to put his foot on it and start to play.  How much intellect does a 2.5 month old have?  Did he work it out himself or is this instinct?