The concept of the Triune Brain was developed by neuroscientist Paul D. MacLean in the 1960s. It describes the brain as having three distinct layers that evolved over time: the reptilian brain, the limbic system, and the neocortex. Each layer is associated with different functions, from basic survival instincts to complex reasoning and emotional processing. The reptilian brain controls fundamental survival functions like heart rate and breathing. The limbic system is involved in emotions and memory, while the neocortex is responsible for higher-order thinking, problem-solving, and language. This model helps explain how different brain regions contribute to behavior and decision-making.