I am a professor in the Psychological Methods Group at the Psychology Department of the University of Amsterdam and director of its Social and Behavioural Data Science Centre. My research focuses on the conceptual analysis of psychometric concepts, the development of new psychometric techniques, and the formation of formalized psychological theory. My research on the use of complex systems and network models in the context of psychometrics and psychopathology research is concentrated in the Psychosystems Project. Research on formal theory construction is located at the Theory Methods Lab. I am an associate of the Institute for Advanced Study and an affiliate of the POLDER simulation center. This website collects my columns, scientific publications, and other work.