Description: The paper will review and critically examine the concept of "learning trajectory" in the literature on professional learning and communities of practice. These theoretical frameworks tend to focus on embedded and "tacit" formats of knowledge and are less attentive to the commitment of expert groups to a domain of knowledge and to the expansion of object-centered environments in modern working life (Knorr Cetina, 1999). Methodology: The discussion of conceptual issues will be supported by interview data and field observations of interactive designers and "boundary crossers" in traditional trades like engineers, nurses, teachers and accountants. By using the concept of "epistemic trajectories" in professional learning we emphasize its object-related aspects rather than the social and life-related (Nespor, 1994). A "decentered" understanding of the motivational bases for professional performance will be proposed. Conclusions: The framework provides a new way of guiding the development of research instruments that is sensitive to both time-space compression and distanciation of learning processes (documentary data, survey data, trajectory analysis and qualitative interviewing). The longitudinal research design will allow comparisons to be made between students in nursing, teaching, engineering, interactive design and accounting in their time of graduation and in their first years at work.