More is less: multidisciplinarity and the dynamics of scientific knowledge

This paper develops a simple model of academic research to analyze knowledge flows within a research system, when demand for multi-disciplinarity varies. Scientists are embedded in departments, linked to all others in the department, as well as to a small number of others outside the department. Pairs of scientists collaborate to produce 'papers'. They can collaborate successfully with their direct links provided the distances in knowledge space between partners are within specified upper and lower bounds. By creating new knowledge, co-authors converge in their knowledge endowments, and the distance between them can fall below the lower bound. This is mitigated in two ways: extra-departmental links; and an intermittent job market in which scientists can change departments. In a simulation model we find that increasing the extent of extra-departmental links, and increasing job market activity both improve aggregate knowledge production. These two modes of knowledge diffusion are, however, substitutes rather than complements: increasing both does not improve performance over increasing only one. In addition, we find that increasing demands for multi-disciplinarity (essentially increasing the lower bound on knowledge distance for effective collaboration) generally decreases knowledge production.