I totally agree with you on the notion that we believe what we think we are.
Identification with certain character traits is a very strong force within us. Even to the point that one believes he is this or that type - maintaining a self image - but does not appear in this way to his social group.

I am always a sceptic when it comes to psychological related studies. There is a risk in taking them for granted but as we all know we can highly influence the outcome of a study by the method itself even though you use double blinds. I am talking about the very use of questions and how interviewees manipulate their answers on a subconscious level. The answer often is influenced by the desire of a person, not so much by the real facts.

Overall, I think that studies nevertheless are telling about tendencies and are not wrong but they also are not totally correct.
Because I do think that way I was researching other methods of questioning and measurements. I found one particular method, further developed by Peter Kruse, who found the origin of this method in the work of George A. Kelly, an American psychologist named "Repertory Grid".

The repertory grid is an interviewing technique which uses nonparametric factor analysis to determine an idiographic measure of personality

In the course of questioning the interviewee loses track of his own answers and the measurement of this technique takes in what he answers on a more intuitive and undetermined level.

I think I will probably make another article about it.

My own position mirrors what you said here. I think there is no "versus" in between of nurture and nature. And I think this discussion is actually disturbing and also blocking that people become more relaxed. As it creates a gap between people and they either tend to the notion of biological or sociological forces influencing us humans.

What I like the best about your article is that accepting and integrating what one finds as a quality of ones own (introvert or extrovert) in a positive way instead of wanting to eliminate a quality and change on a whole.

I wouldn't go that far as to say that it's factual that one is born with or develops certain character traits in childhood then loses them through adolescence and then gains them back in older age. This in itself could already be a believe system. ... Funnily though, one could say if a society on a whole does maintain a believe system this is reality (even if it's not).

What I observed is that when I concentrate on the details and I watch people I know really good than there patterns of behaving indeed do change quite significant depending on how relaxed they feel within a group or with a talking partner. A friend of mine who is usually introvert and sees herself as such can become a maniac and a really outgoing person when she is in a good mood, when she drinks alcohol and in particular, when she is surrounded by people who she rates less confident compared to herself.

People, for example, who usually overtake the lead in a group or have a tendency in doing so, drop this attitude when another person comes along who has an even stronger ability in leading a group. For example, I am strong in classes and people start to rely on me. There, I am extrovert and confident. But take me to a forrest and a hike, I stop being a leader and "obey" to the one who is in charge, becoming more quiet in observing how to behave.

When people are not flexible and never drop their attitudes than I relate this to the notion and deep conviction that they might not develop the idea that this could even be possible or that they really do not care at all about personal development. These are only some reasons but altogether I think that changing does take place in a lifetime.

We could argue though about core traits or the very "essence" of ones personality. But as always I never would carve things in granite ;-)

Thanks for giving me some nutrition to chew on!