In recent years, one can observe an increasing interest in dynamic models in the personality psychology research. Opposed to the traditional paradigm—in which personality is recognized as a set of several permanent dispositions called traits—dynamic approaches treat it as a complex system based on feedback loops between individual and the environment. The growing attention to dynamic models entails the need for appropriate modelling tools. In this conceptual paper we address this demand by proposing a new approach called personality-in-the-loop, which combines state-of-the-art psychological models with the human-in-the-loop approach used in the design of intelligent systems. This new approach has a potential to open new research directions including the development of new experimental frameworks for research in personality psychology, based on simulations and methods used in the design of intelligent systems. It will also enable the development of new dynamic models of personality in silico. Finally, the proposed approach extends the field of intelligent systems design with new possibilities for processing personality-related data in these systems.