The three-brain theory is a theory proposed by Paul McLean, an American neuroscientist, in 1970.
The three-brain theory divides the human brain into three types: one is the instinctive brain, which is about 6-700 million years old, when reptiles reacted instinctively to survival problems due to their own physical reasons. For example, when you encounter danger, you run, when you encounter food, when you encounter food, you chase when you meet your favorite object, which is the most basic brain that ancient creatures evolved to satisfy survival, also known as the reptilian brain, etc.
The second type of brain is the emotional brain, which dates back about 200 million to 300 million years, when marine animals slowly evolved into reptiles, and they slowly marched to land. While reptiles themselves are physically unable to adapt to changes in their environment, mammals emerge with thermostatic systems that are better able to adapt to their environment and evolve emotions. With emotions, animals can choose to survive in a favorable and comfortable environment. This is also the current situation of most of our lives, like emotional feelings, although they are very fat, but others will be happy when they say that they are in good shape, sometimes we know that we are not very good in some aspects, but others still make us happy with a compliment against their will.
The third type is the rational brain, which appeared about millions of years ago. It's the brain we think is the most powerful, and it's located in the frontal lobe, in the cerebral cortex. The rational brain is not what we think can easily respond to our various events, because the powerful existence of the instinctive brain and the emotional brain, they will firmly control us, they think that we are still in the wild era, use instinct to protect our safe survival, use happy emotions to make ourselves happy, let the intelligent rational brain explain the reason, who made you so smart?
Someone has made a rough comparison, if the instinctive brain is 100 years old, the emotional brain is 55 years old, and the rational brain is a baby less than a year old, so you can understand why instinct and emotions always prevail.
The instinctive brain matures at about 2 years of age, the emotional brain matures at about 12 years of age, and the rational brain matures around 22 years old.
Although the three-brain theory is not recognized in the scientific and medical circles now, it still has reference value for psychology, allowing us to better understand people's behavior and cognition in different periods.