If all one knows is one's own culture, one has only met one person. Those who know no culture but their own tend to be narcissistic, simply because they've never known anyone else to have a relationship with. 

Much of what we understand as unique personality is simply the mask (persona) of culture. Psychology since Freud has placed great importance on childhood experience and particularly the role that parents play in shaping personality. Of course, parents do not fall from the skies and are themselves the products of culture.

-Laurence G. Boldt