Why do academic scientists engage in interdisciplinary research?

We introduce a measure of interdisciplinarity as the diversity of academic research production across scientific domains. Our dataset concerns more than 900 permanent researchers employed by a large French university which is ranked first among French universities in terms of impact. As expected we find that the traditional academic career incentives do not stimulate interdisciplinary research, while having connections with industry does. The context of work in the laboratory (size, colleagues' status, age and affiliations) strongly affects the propensity to undertake interdisciplinary research.