Gjalt-Jorn operates at the intersection of open science, open infrastructure, behavior change science, psychology, and theory and methodology. He was involved in the development of several applications for qualitative research, quantitative research, evidence synthesis, and open science practices. He is interested in the epistemological, theoretical, methodological, and operational requirements for moving towards true interoperability for the social and behavioral sciences, as well as in the spectrum that runs from accurate modeling of complex data with open standards on the one end to simplified, user-friendly applications that support real-world impact on the other hand.