The Myth of the Reptilian Brain: Why Is the Triune Brain Model Scientifically Wrong?

The reptilian brain idea, long common in general psychology, is now considered by neuroscience to be an inaccurate picture of brain evolution.

Zomit: The idea of ​​the reptilian brain, which was popular in general psychology for many years, is today considered a false picture of brain development in terms of neuroscience.

The idea of the "reptile brain" has been repeated for years in general psychology books, self-help courses, and even management training. According to this view, there is a primitive and instinctive part deep in our brain that is responsible for behaviors such as fear, aggression, sexual desire and sudden reactions, and the more rational part of the brain must restrain it. This explanation is simple and attractive, but today's neuroscience does not consider it an accurate picture of the structure and development of the brain.

The roots of this idea go back to the model that Paul D. McLean, an American neuroscientist, proposed in 1959. He considered the human brain to be a set of three evolutionary parts that are gradually superimposed on each other. This view was later known as the "triple brain model".

According to McLean's model, the oldest part of the brain was the "reptilian brain," which was inherited from our common ancestor with reptiles and controls basic behaviors related to survival, foraging, and reproduction.

The next layer in this model was the "mammalian brain", which included the limbic system and was considered the center of emotions. MacLean hypothesized that this part allowed for behaviors such as child care, play, and simple forms of social communication in mammals.

The triple brain model, which divides the human brain into reptilian, mammalian and rational parts, is not considered scientifically valid today.

In the outermost part, there was the cerebral cortex, which was called the "neo-mammalian brain" in McLean's model. This part was attributed to abilities such as language, reasoning, and logical decision-making, and was supposed to control the primitive impulses and emotional reactions of the two older parts.

In such a picture, human behavior was the result of competition between three systems. Impulsive decisions, anger, or preference for immediate reward over long-term gain could be seen as the result of the "reptile brain" taking over.

The problem is that today's evidence does not support such a three-layered structure. The evolution of the brain did not happen in such a way that first a "reptilian brain" was made, then the emotional part of mammals was added on top of it, and finally humans got a new logical layer. Different parts of the brain have undergone simultaneous changes over millions of years, developed different evolutionary branches, and have complex relationships with each other.

Some of the evidence that was once used to support McLean's model was later questioned. For example, structures once thought to be specific to the "mammalian brain" are also found in some reptiles.

On the other hand, features that were previously attributed to the "neo-mammalian brain" and so-called advanced animals are also present in many other species. Different animals can solve problems, learn from experience and emotion, make decisions about the future, and communicate with each other in complex ways.

Guy Lechshiner, a neurologist at Guy's and St Thomas' Hospital in London, says that it is well accepted that different parts of the brain have different functions; But the evolutionary and physiological evidence does not support the idea that the human brain is composed of several independent layers. According to him, some basic functions of the brain are very old in the history of evolution, but it is not possible to identify three separate systems that control instincts, emotions, and logic.

Lisa Feldman Burt, professor of psychology at Northeastern University, is also one of the researchers who opposes the concept of "reptile brain". In his view, the brain is not a battlefield between instinct, emotion and logic.

The brain acts more like an integrated and dynamic system whose different parts are constantly communicating with each other. One of the main tasks of this system is to predict the needs of the body and manage resources such as energy so that the body can maintain its internal conditions and survive.

Simply put, a "primitive" part of the brain usually cannot be said to take over from the "logical" part when making a decision or reacting emotionally. Emotion, memory, perception, body posture and previous experiences can all play a role in the formation of behavior at the same time.

Despite its scientific weaknesses, the triad brain model is still taught in some introductory psychology books. Researchers have warned that continuing to use this model could create a false impression of evolution.

One of the problems is that such a model presents humans as the final stage or "peak" of evolution; It is as if other species are more dominated by instinct and humans are separated from them due to having a new logical part in the brain.

Today's neuroscience considers the brain as an integrated and interconnected system in which emotion, memory, body posture and reasoning interact.

But evolution does not have a linear and predetermined path that leads organisms from simple to complex and finally to humans. Different species have evolved along separate paths, and many of the abilities once thought to be unique to humans are found in forms in other animals. For example, delaying reward, that is, giving up an immediate benefit in order to achieve a better result in the future, is not a completely exclusive human behavior.

The question remains as to why the concept of the "reptilian brain" remains popular despite the rejection of much of its scientific basis.

One of the reasons is probably its simplicity. Dividing the human mind into instinct, emotion and logic is a framework that is easily understood and remembered. The model also offers a simple explanation for complex behavior: if we make a bad decision or get angry, it can be attributed to the "primary part" of the brain.

But the real brain does not have such clear boundaries. Today's knowledge shows that the brain is not a collection of independent and competing layers, but a highly interconnected network. The parts that are involved in emotional processes can also be involved in decision-making and memory, and the areas related to reasoning do not work separately from body posture and emotions.

As a result, the term "reptile brain" may still be used as a metaphor in everyday conversation, but it should not be considered a precise scientific explanation of brain structure or human behavior.