Abstract Operant boxes enable the application of complex behavioural paradigms to support circuit neuroscience and drug discovery research. However. commercial operant box systems are expensive and often not optimised for combining behaviour with neurophysiology. Here we introduce a fully open-source Python-based operant-box system in a 5-choice design (pyOS-5) that enables assessment... https://www.chincoponydrillteam.com/product-category/burner-cap/