Social experience is how we learn about ourselves. We never truly know how we would react to something until we have experience it. It is amazing to witness the variability in our actions when we are faced with difficulty. By experiencing life we discover who we are and who we want to be.
Human personality is very complex and there are many factors that contribute to the formation of personality. I think saying that social experience is the key to human personality is a bit too specific. Personality has to do with many things.
Human personality is formed through genetics, social experience, personal experience, beliefs, etc. I would say that social experience plays a role in that our experiences throughout our life time shapes us. For example, if we were raised by parents who were very negative all of the time then chances are we may become this way as adults. This is a part of learned behavior. This is just one aspect of personality though. There are many other things to consider.
In any question such as this, trying to find "the key" is problematic. Such a complex issue such as the formation of human personality involves many elements that converge and interact with one another, sometimes simultaneously. In the end, trying to distinguish the role of different elements might prove to be more worthwhile than trying to find "the key" entity. I would say that social interaction is one of the compelling elements that helps to form human identity. The culture to which we belong, the people with which we associate, as well as interactions we forge help to formulate who we are and how we perceive reality.
Personality development depends a lot on social mixing and exposure. The more a person participates in life out-of-doors, the more experienced he/she would be. Growth always requires more space, and the limited family space must open itself into larger social space. A person confined to his/her domestic space is bound to be self-centred; interacting with the endless varieties of life, an individual becomes a social, or rather, a human being.
Society is a muti-dimensional reality. Experiences of that reality truly hold the key to the growth and maturity of a person. A log of wood gets seasoned by being in the sun and the rains for months together; that's exactly what happens to a human personality.
Personality refers to the totality of the ways in which an individuals behaves in terms of acting and reacting with others. It is usually described in terms of traits exhibited by the person. There is no common list of personality traits agreed by all experts. However the list generally includes such as extroverted versus introverted, sensing versus intuitive, thinking versus feeling, perceiving versus judging.
The personality may be dependent to some extent to hereditary factors. But the biggest influence on formation of personality is the environment within which the individual lives and the nature of his or her experience within this environment. Within the environment the greatest influence is that of the culture.
The culture within which a person is raised establishes the norms, attitudes and values that are passed on from one generation to next. Also the individual experience of the individual within the culture also impacts the personality. The kind of situation faced by the situations faced by the individual in early life, determines the kind of responses the individual finds more appropriate and which the individual uses ans practices more gaining greater skill in particular type of behavior. For example, the development of traits like being extroverted or introverted is very much influenced by early experience of the individual with behaving in these different ways. One who has experienced success and satisfaction in early life by extroverted behavior is more likely to use this type of behavior, and in the process become more skilled in the process.
Social experience makes one aware of the facts and incidents taking places around him. It transforms him from such a person who is narrow-minded with a limited vision into an open-minded human. It opens a new window before him. He gets the opportunity to come in contact of various types of people; this diversity helps his personality nourish. Moreover, through social experiences, he gets better chance to work for humanity purpose, for instance, he gets more scopes to work as a social worker, and to render service for the betterment of the society being a part of an organization or being individual. The man who has never undergone any social experience, can never be a profound human being. In fact, social works are a part of the culture.
That is how, social experience is key to human personality.