Hello Rita,
you are right about the fact that a psychiatrist or any other therapist deals with people who have covered already a good deal of their lifetime. What really is in a baby is mere guessing. After about 4 or 5 years a child is more or less "finished" and is equipped with his/her views about life etc. Lifestyle, as IP people call it. So we only witness the outcome of 4 or 5 years influence of the invironment in its broadest sense, AND all the conclusions a young child has drawn about all this environmental encounters. We hardly can communicate well with a child of 2 or 3 years of age about his/her interpretations about life. That is mere guessing, and sure, often are these guesses absolutely right.
Concerning the growth of a feeling of inferiority, I guess ( ) that it depends also on environmental interaction with all the evaluations concerning these interactions that are sent out to the young child. One point of IP is that it is the youngster that in the end has the last word, so to speak, or to put it differently, decides about the value of the interactions. Yet, here too, we might find outcomes that are obvious, that are in the line of "common sense", that are to be expected. Feelings of inferiority as such should not be seen as a personal disaster, as in fact they propel us to make discoveries and to produce things that make life easier for us and for the whole of mankind.
Paul