Nikolai Haahjem Eftedal is a psychological researcher from Norway. He earned his PhD in psychology from the University of Oslo, using behavioral-genetics approaches to understand the etiology and structure of socio-political attitudes. He is affiliated with the Promenta Research Centre, also at the University of Oslo, where he studies the causes of family resemblance in socio-economic and psychiatric outcomes. He specializes in registry data and the concurrent modelling of correlations from large sets of categories of relatives. His email is n.h.eftedal@psykologi.uio.no.