Carlone, H., Cook, M., Wong, J., Sandoval, W. A., Barton, A. C., Tan, E., & Brickhouse, N. (2008, June). Seeing and supporting identity development in science education. In Proceedings of the 8th international conference on International conference for the learning sciences-Volume 3 (pp. 214-220). International Society of the Learning Sciences.
Although education is not my field, my work in digital identity has taught me the identity and identity formation are complex social and cultural practices.
I'd second the reference to G.H.Mead's work "The I and the Me", some of Modigliani's paintings are a great illustration of the concept of intrinsic and extrinsic identity too.
However, identity could be modelled as a triple: endo; meso; and exo-identity. Who you think you are, how you present to others, and how others perceive your identity.
Meanwhile Ettore Recchi's work on European identity formation presents two contrasting identity formation models: "Structuralism" and "Culturalism". Structuralist identity formation is bottom-up and characterised by association and interaction. Culturalist identity formation is top-down and characterised by exposure and persuasion.
I hope that helps, good luck.
Robert
Recchi, Ettore. 2012. ‘Transnational Practices and European Identity: Theoretical foundations, research developments and policy implications. Paper presented at the conference The Development of European Identity/Identities: Policy and Research Issues, European Commission, Brussels, 9 February 2012.
EC (2012), “The Development Of European Identity/Identities: Unfinished Business”