Abstract
This Article studies the change in behavior over time for the professional actors in the international investment arbitration system. Using the results from a large-scale computational analysis, I find indications that the actors have increased their use of citations and their use of terms that originate outside of the litigated treaties. In light of these findings, I argue that the actors are increasingly challenging the insulated structural outset of international investment law with a more systemic approach to legal reasoning. Subsequently, I explore if theories from the realm of cognitive science may provide explanations for why the actors are changing their behavior and what consequences such cognitive mechanisms may have on the systems development.