40 Years of Multiple Social Categorization: A Tool for Social Inclusivity

We review a 40-year corpus of research that we collectively name “Multiple Categorisation Theory” (MCT). From early illustrations using the minimal group paradigm, through a focus on how people cognitively represent social diversity, to recent models of outgroup “re-humanisation”, this work has revealed much about how we think about inclusivity, exclusion, and intergroup differences. We review research that assessed ways to reduce intergroup bias by attenuating the reliance on simple categorisation via “crossed categorisation”. We describe how this research evolved from a focus on intergroup differences to incorporate self-categorisation, through processes of decategorisation and increased social identity complexity. Finally, we consider contemporary models that reveal the generalised benefits of multiple categorisation in promoting outgroup “re-humanisation” through “cognitive liberalisation”. We conclude by highlighting the theoretical and practical implications of this research programme.