An institution’s ability to shape behavior is affected by other institutions that are also active – and the legacy of institutions that preceded it. What North described as an “institutional matrix” is a research domain of nearly untapped potential, but it requires new methodological approaches. In this chapter the author suggests one approach to modeling the connection between institutions, Games +, which considers multiple games simultaneously. Connections between games take shape as behavioral spillovers, the way that people employ familiar behaviors as an initial approach to a novel situation. Using a Games + approach is a tool to provide insight into two fields of institutional research: the relationship between culture and institutional performance, and robust institutional design.