John Charles Turner (September 7, 1947 – July 24, 2011) was a British social psychologist who, along with colleagues, developed the self-categorization theory.
Amongst other things the theory states that the self is not a foundational aspect of cognition, but rather that the self is an outcome of cognitive processes and an interaction between the person and the social context.
Self-categorization theory was developed as a companion theory to the social identity theory, and the two theories taken together are known as the social identity approach.