The article "Group-Level Self-Definition and Self-Investment: A Hierarchical (Multi-Component) Model of In-Group Identification" by Leach, van Zomeren, Zebel, Vliek, Pennekamp, Doosje, Ouwerkerk, and Spears, published in the *Journal of Personality and Social Psychology* in 2008, explores the psychological and social significance of individuals' identification with in-groups. The authors identify five specific components of in-group identification: individual self-stereotyping, in-group homogeneity, satisfaction, solidarity, and centrality. These components are organized into two broader dimensions: group-level self-definition (individual self-stereotyping and in-group homogeneity) and self-investment (solidarity, satisfaction, and centrality). The study uses confirmatory factor analysis to validate the proposed model across three different group identities (Dutch, European, and University of Amsterdam) and examines the construct validity of the five components through correlations with established measures of in-group identification. Additionally, the study demonstrates the predictive and discriminant validity of the components by examining their impact on individuals' orientation to and emotions about real intergroup relations. The findings support the value of a hierarchical, multicomponent model of in-group identification, providing a more nuanced understanding of how individuals perceive and invest in their in-groups.The article "Group-Level Self-Definition and Self-Investment: A Hierarchical (Multi-Component) Model of In-Group Identification" by Leach, van Zomeren, Zebel, Vliek, Pennekamp, Doosje, Ouwerkerk, and Spears, published in the *Journal of Personality and Social Psychology* in 2008, explores the psychological and social significance of individuals' identification with in-groups. The authors identify five specific components of in-group identification: individual self-stereotyping, in-group homogeneity, satisfaction, solidarity, and centrality. These components are organized into two broader dimensions: group-level self-definition (individual self-stereotyping and in-group homogeneity) and self-investment (solidarity, satisfaction, and centrality). The study uses confirmatory factor analysis to validate the proposed model across three different group identities (Dutch, European, and University of Amsterdam) and examines the construct validity of the five components through correlations with established measures of in-group identification. Additionally, the study demonstrates the predictive and discriminant validity of the components by examining their impact on individuals' orientation to and emotions about real intergroup relations. The findings support the value of a hierarchical, multicomponent model of in-group identification, providing a more nuanced understanding of how individuals perceive and invest in their in-groups.