Research on collective emotion spans social sciences, psychology and philosophy. There are detailed case studies and diverse theories of collective emotion. However, experimental evidence regarding the universal characteristics, antecedents and consequences of collective emotion remains sparse. Moreover, current research mainly relies on emotion self-reports, accounting for the subjective experience of collective emotion and ignoring their cognitive and physiological bases. In response to these challenges, we argue for experimental research on collective emotion. We start with an overview of theoretical frameworks to (...) identify a set of three characteristics of collective emotion. Based on research in cognitive and affective sciences, we then examine the corresponding candidate mechanisms. Finally, we highlight outstanding questions, review experimental evidence, and suggest ideas for future experimental research. (shrink)