The cognitive science of religion has made a persuasive case for the view that a number of different psychological systems are involved in the construction and transmission of notions of extranatural agency such as deities and spirits. Until now this work has been based largely on findings in experimental psychology, illustrated mainly with hypothetical or anecdotal examples. In The Mind Possessed, Emma Cohen considers how the psychological systems undergirding spirit concepts are activated in real-world settings. Spirit possession practices have long had a magnetizing effect on academic researchers but there have been few, if any, satisfactory theoretical treatments of spirit possession that attempt to account for its emergence and spread globally. Drawing on ethnographic data collected during eighteen months of fieldwork in Belem, northern Brazil, Cohen combines fine-grained descriptions and analyses of mediumistic activities in an Afro-Brazilian cult house with a scientifically-grounded explanation for the emergence and spread of ideas about spirits, possession and healing. Cohen shows why spirit possession and its associated activities are inherently attention-grabbing. Making a radical departure from traditional anthropological, medicalist, and sociological analyses, she argues that a cognitive approach offers more precise and testable hypotheses concerning the spread and appeal of spirit concepts and possession activities. This timely book presents new lines of enquiry for the cognitive science of religion (a rapidly growing field of interdisciplinary scholarship) and challenges the theoretical frameworks within which spirit possession practices have traditionally been understood.