This article examines the introduction of social sciences, particularly psychology, to the emerging arena of technical assistance and training in the establishment of Swedish aid in the 60s and 70s. Departing from the assumption of Swedish aid workers as situated at the intersection between conflicting ideals, such as philanthropic, miliary, anti-imperialist, business and statal discourses, the purpose is to further unfold what ideological tensions were at play in early literature written for AWs, experts and volunteers. With inspiration from the concept of ‘psy disciplines’, three argumentative textbooks written by scholars and practitioners in 1965–1973 are studied. The research questions ask: What kind of discourses were brought to the local Swedish context of technical assistance and development training when advocating for psy expertise in this new vocation? How are they merging with other ideological tensions within development assistance? How can we understand them in their historical context and in the light of research on development training? The results show a linkage between psy theories and the recruitment practices of the American Peace Corps, travelling to and merging with the Swedish context in specific ways.