Dominic Abrams is Professor of Social Psychology and Director of the Centre for the Study of Group Processes at the University of Kent at Canterbury. His research expertise includes social identity and intergroup relations (e.g., the contact hypothesis, nationalism, collective protest, contemporary aspects of prejudice), deviance (particularly the subjective group dynamics model) and social identity in organizational contexts. He is the President of the Society for the Psychological Study of Social Issues, co-editor of Group Processes and Intergroup Relations, and co-editor of The Social Psychology of Inclusion and Exclusion (2005) with M.A. Hogg and J. M. Marques.Melanie Killen is Professor of Human Development and Quantitative Methodology, Professor of Psychology (Affiliate), and the Associate Director for the Center for Children, Relationships, and Culture at the University of Maryland.  Her research expertise includes the development of social inclusion and exclusion, moral reasoning, intergroup attitudes, prejudice, and bias in peer groups, peer interactions and social relationships in childhood and adolescence. She is Associate Editor of the journal Child Development, co-author of Children and Social Exclusion: Morality, Prejudice and Group Identity (2011) with Adam Rutland, and Editor of the Handbook on Moral Development (2006, 2014) with Judith Smetana.

• INTRODUCTION  Social Exclusion of Children: Developmental Origins of PrejudiceDominic Abrams and Melanie Killen 1   SECTION I: PSYCHOLOGICAL FOUNDATIONS OF INCLUSION AND EXCLUSION  Peer Group Rejection in Childhood: Effects of Rejection Ambiguity, Rejection Sensitivity, and Social Acumen Drew Nesdale, Melanie J. Zimmer-Gembeck, and Natalie Roxburgh 11 When Do Children Dislike Ingroup Members?: Resource Allocation from Individual and Group Perspectives Kelly Lynn Mulvey, Aline Hitti, Adam Rutland, Dominic Abrams, and Melanie Killen 28  Does Moral and Social Conventional Reasoning Predict British Young People’s Judgments About the Rights of Asylum Seeker Youth?  Martin D. Ruck and Harriet R. Tenenbaum 46 Do Adolescents’ Evaluations of Exclusion Differ Based on Gender Expression and Sexual Orientation? Justin E. Heinze and Stacey S. Horn 62   SECTION II: REVEALING AND CHALLENGING EXCLUSION NORMS  Of Affect and Ambiguity: The Emergence of Preference for Arbitrary IngroupsYarrow Dunham and Jason Emory 80  How Young Children Evaluate People With and Without Disabilities Lauren K. Huckstadt and Kristin Shutts 98  Can Fostering Children’s Ability to Challenge Sexism Improve Critical Analysis, Internalization, and Enactment of Inclusive, Egalitarian Peer Relationships? Erin Pahlke, Rebecca S. Bigler, and Carol Lynn Martin 113  Ethnic Classroom Composition and Peer Victimization: The Moderating Role of Classroom Attitudes Jochem Thijs, Maykel Verkuyten, and Malin Grundel 132 How Peer Norms of Inclusion and Exclusion Predict Children’s Interest in Cross-Ethnic Friendships Linda R. Tropp, Thomas C. O’Brien, and Katya Migacheva 149 What Makes a Young Assertive Bystander? The Effect of Intergroup Contact, Empathy, Cultural Openness, and In-Group Bias on Assertive Bystander Intervention IntentionsNicola Abbott and Lindsey Cameron 165   SECTION III: COMMENTARY  Intergroup Social Exclusion in Childhood: Forms, Norms, Context, and Social IdentityMark Bennett 181