This article analyses how applied psychology redefined societies' views on abilities and disabilities during the early twentieth century. It studies the making of this new knowledge as two interrelated processes: first, the experimental laboratory developments of scientific knowledge, and second, the translation of quantitative techniques for measuring intelligence and aptitudes into real‐life situations for political reasons. The two unified processes ‘scientification’ and ‘politicisation’ point to how abilities and aptitudes were redefined due to scientific and political authorities and interests. This article aims to give a critical overview of the international innovations of applied psychology analysed as ‘social technologies’, and how these technologies transformed the Norwegian educational and vocational systems. The main empirical sources are seminal professional and political texts.