Title: MANSA: LEARNING FAST AND SLOW IN MULTI-AGENT SYSTEMS WITH A GLOBAL SWITCHING AGENT. Abstract: In multi-agent systems, independent learners (IL) often show remarkable performance and easily scale with the number of agents. Yet, training IL can sometimes be inefficient particularly in states that require coordinated exploration. Using observations of other agents’ actions through centralised learning (CL) enables agents to quickly learn how to coordinate their behaviour but employing CL at all states is prohibitively expensive in many real-world applications. Besides, applying CL often needs strong representational constraints (such as individual-global-max condition) that can lead to poor performance if violated. In this paper, we introduce a novel IL framework named MANSA that selectively employs CL only at states that require coordination. Central to MANSA is the additional reinforcement learning (RL) agent that uses switching controls to quickly learn when and where to activate CL so as to boost the performance of IL while using only IL everywhere else. Our theory proves that MANSA’s switching control mechanism, which can seamlessly adopt any existing multi-agent RL (MARL) algorithms, preserves MARL convergence properties in cooperative settings. Importantly, we prove that MANSA can improve performance and maximise performance given a limited budget of CL calls. We show empirically in Level-based Foraging and SMAC settings that MANSA achieves fast, superior training performance through its minimal selective use of CL. 