Members within a group must not just be more similar with each-other than different from other groups (comparative fit).  They must also have the similarities and differences that are consistent with our beliefs and theories about the particular group (the perceived social meaning of the social category)

Normative fit of self-categorization

A collection of stimuli is more likely to be categorized as a group if the perceived average difference among them (intragroup difference) is less than the perceived average difference between them and the remaining reference stimuli (intergroup difference).

Comparative Fit of Self-Categories (Metacontrast)

The fit of the self-category is based on two aspects (Turner et al. 1987):
- 1) The comparative fit (metacontrast)
- 2) The normative fit

University of Michigan - Ann Arbor

The variation of how people self-categorize is a rule rather than exception. Variation is dependent on two factors (Oakes 1987):
-  1) the "readiness" of the individual to adopt the categorization (relative accessibility)
- 2) the "fit" of the categorization and the "stimulus reality" being represented

Fit/Readiness Hypothesis of self-categorization

Turner, J. C., Oakes, P. J., Haslam, S. A., & McGarty, C. (1994). Self and collective: Cognition and social context. Personality and social psychology bulletin, 20(5), 454-463.

 Self and collective: Cognition and social context (Turner 1994)

Fit of self-categories

Refers to how a person's past experiences, and current expectations, motives values, goals and needs are influential in deciding how the perceiver "selects" and "uses" particular self-categories based on how central, relevant and advantageous they may be at present (Gurin and Markus 1988).

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