The Visiting Research Professorship focuses on the theme of “effort and social inequality”. Effort is a crucial factor in normative accounts of distributive justice as well as in scientific theories of unequal life chances. But it is also notoriously difficult to measure effort, leaving existing empirical research lacking and public discourse on issues such as meritocracy imperfectly informed. The professorship will scrutinize both the determinants and consequences of cognitive effort, building on the work of the WZB Research Group “Effort and Social Inequality” (2018-2024). The research group has harbored the German part of the ERC project EFFORT, which has collected novel laboratory data of a large sample of fifth-grade students in Berlin and Madrid. The Visiting Research Professorship shall further leverage this potent and novel data set alongside complementary data sources to open the black box of effort. The goal is to advance our understanding of effort’s antecedents and consequences, including a cross-country comparison between Germany and Spain. Rooted in social stratification scholarship, this research program features an interdisciplinary component, drawing on insights from cognitive and personality psychology as well as behavioral and applied economics.