Couple of handy references for you:

Hogg, M.A., & Terry, D.I. (2000). Social identity and self-categorization processes in organizational contexts. Academy of Management Review, 25(1), 121-140.

Hogg, M.A., & Reid, S.A. (2006). Social Identity, Self-Categorization, and the Communication of Group Norms. Communication Theory, 16(1), 7-30.

Haslam, S.A., Powell, C., & Turner, J. (2000). Social Identity, Self-categorization, and Work Motivation: Rethinking the Contribution of the Group to Positive and Sustainable Organisational Outcomes. Applied Psychology, 49(3), 319-339.

Mandy, A., Milton, C., & Mandy, P. (2004). Professional stereotyping and interprofessional education. Learning in Health and Social Care, 3(3), 154-170.

Read this: http://www.psychologie.uni-frankfurt.de/51624871/Hornsey-2008.pdf

It is a question that is up to the area of knowledge of psychology, but I can say that an important element in understanding the behavior of a person is the formation of character through the practice of virtues.

Social Identity Theory introduces a way of explaining intergroup behaviours, particularly the discrimination of in-group members (‘us’) against out-group members (‘them’). Self-Categorisation Theory focuses on individuals who tend to categorise themselves into certain psychological groups in a given context in which a series of values and interpretations are shared.

Here are some good readings:

Turner, J. C. & Reynolds, K. J. (2010). The Story of Social Identity. In: Rediscovering Social Identity: Key Readings, Postmes, T. & Branscombe, N. R. (eds.), pp. 13-32. Psychological Press, New York.

Turner, J. C. (1987). A Self-Categorization Theory. In: Rediscovering the Social Group: A Self-Categorization Theory, Turner, J. C., Hogg, M. A., Oakes, P. J., Reicher, S. D. & Wetherell, M., S. (eds.), pp. 42-67. Blackwell, Oxford, UK.

Hogg, M. A. & Terry, D. J. (2000). Social Identity and Self-Categorization Processes in Organizational Contexts. Academy of Management Review, 25, 121-140.

Ashforth, B. E. & Mael, F. (1989). Social Identity Theory and the Organization. Academy of Management Review, 14, 20-39.

Social identity theory encompasses the concept of how social identityof an individual facilitates him or her to categorize people or groups as in-group or out-group through social categorization process. this is to remember that initially personal identity and social identity of a person remain dinstinct but when social categorization process starts the social identity constitutes a part of self -identity which basically categorise groups through social comparison and attraction-similarity paradigm as in groups and outgroups.

Yes - I am late. But since I don´t really consider the above "satifactory enough" and "to the core point", let me add my two cents:

SIT: Is all about "us versus them" (we versus they); including “mechanisms” to increase or stabilize the own status of the in-group --- or to leave it (for a better in-group); hence, "motivational" processes.

SCT: At different times, we perceive ourselves as unique individuals (self-concept) or as members of groups within different levels of abstraction (ingroup-outgroup; superordinate groups). It is this change in self-categorization that determines the individuals’ perceptions, attitudes and behavior. In addition the SCT goes deeper into the cognitive (rather than motivational as within the SIT) processes.

The SCT predicts a generall accentuation of in-group similiarities and out-group differences.

(In addition, the "Turner-" and "Hogg"-references as stated above are, indeed, the right sources!)