This paper tests social identity theory with respect to individuals' self-identification behavior. We report results from a laboratory experiment in which subjects choose their group membership, which is interpreted as decision to identify with the respective group. Inducing a trade-off between monetary payoffs and different group identification choices we elicit the respective implicit valuations of identifying with different groups. The variation of these valuations is in line with the predictions from social identity theory: Subjects have a higher valuation for identifying with groups with a higher status and with groups to which they have a smaller social distance. Finally, we show that this behavior predicts individual out-group discrimination in allocation decisions, which has previously been shown to be associated with social identity. Overall our results provide strong support for the notion that individuals optimize behavior with respect to social identity.
