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 social behavior. The reptilian brain controls fundamental life functions such as heart rate and breathing, while the limbic system is involved in emotions and memory. The neocortex is responsible for higher-order thinking, problem-solving, and language. This model helps to understand how different brain regions contribute to human behavior and cognition.