A recent study from Stanford’s Wu Tsai Neurosciences Institute has shed light on the interplay between two key brain chemicals, dopamine and serotonin, revealing their opposing roles in shaping our decisions and learning processes. Published in Nature, the research demonstrates for the first time that dopamine and serotonin operate as a “gas and brake” system, jointly influencing how we learn from rewards. The findings have broad implications, from understanding everyday decision-making to developing treatments for neurological and psychiatric conditions such as addiction, depression, and Parkinson’s disease.