This volume contains some of the materials presented at the international workshop on ``The Cognitive Foundations of Group Attitudes and Social Interaction'' that took place in Toulouse on 31st May- 1st June 2012. The workshop was one of the major events of the European Network on Social Intelligence (SINTELNET) whose aim was to help build a shared perspective at the intersection of artificial intelligence, the social sciences and humanities, to identify challenges and opportunities for cross-disciplinary collaboration, and to provide guidelines for research and policy-making and to kindle partnerships among participants. The workshop was intended to bring together philosophers, social scientists (economists and psychologists), logicians and computer scientists to discuss about the cognitive foundations of group attitudes and social interaction. It dealt with questions such as: \textbullet What are the relationships between individual attitudes such as beliefs, goals and intentions and group attitudes such as common belief, collective acceptance, joint intentions, group preferences and collective emotions? Can group attitudes be defined from the corresponding individual attitudes, and if so, how? What does it mean that a given group of agents has a collective emotion (e.g. collective guilt or shame, panic)? \textbullet What are the cognitive bases of group identity and group identification (i.e. the fact that an agent identifies himself as members of a given group)? Is group identification reducible to the sharing of ideals and values with the other members of the group? How does group identification influence decision in strategic situations (e.g. team reasoning, I-mode vs. We-mode)? \textbullet What is the role of social emotions such as guilt, shame and envy in social interaction? What are the relationships between social emotions and individual attitudes such as beliefs, goals, intentions, values and ideals? How do these emotions influence decisions in strategic situations? \textbullet What are the relationships between trust and individual attitudes such as beliefs, goals and intentions? Does trust have an affective component? If so, what are the relationships between trust and emotions such as hope and fear, joy and sadness? \textbullet Is game theory sufficient to explain and to model social interaction? Are there concepts that are relevant for explaining and modelling social interaction that are missing in game theory? For example, while the notion of intention has been extensively studied in philosophy of mind and AI, it is not included in the conceptual framework of game theory. Is it important to explain social interaction? If so, how game theory should be extended in order to incorporate this notion. The present volume contains ten chapters. They offer a broad perspective on different issues and concepts that are situated at the intersection between different disciplines such as cognitive sciences and social psychology, legal theory, logic and artificial intelligence. This includes the concepts of trust and help, the problem of mental representation, the relationship between individual beliefs and group beliefs, the cognitive structure of social emotions and the cognitive bases of norm compliance. We hope that the material contained in this volume will be useful for improving understanding of the way social concepts and phenomena can be analysed and explained by grounding them on a cognitive foundation.