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The model of the 3 brains: reptilian, limbic and neocortex

The model of the 3 brains: reptilian, limbic and neocortex

May 6, 2021

The human brain is the most complex system known. That means that, if you want to understand its operation, you need to find patterns and regularities in its operation and structure; In other words, we must try to formulate useful and simple explanations about this set of organs.

The triune brain of Paul MacLean , which is sometimes known as the theory of the 3 brains, has been very popular for years for grouping several regions of the brain in different sets that, as proposed by this neuroscientist, perform different tasks. The differentiated structures would be, according to MacLean, the reptilian complex, the limbic system and the neocortex.


Understanding the idea of ​​triune brain

The idea of ​​the triple brain of Paul MacLean is based on the idea that there are 3 different brain systems in the human brain , with its own logics of operation, and that each of them has been appearing in our evolutionary line in a sequential way, one on the other. This means, among other things, that these three brains would be relatively independent and that they would relate to each other following a hierarchy, depending on their age and the importance of their functions for our survival.

The reptilian complex, for example, being the first to appear would be the structure that performs the most basic and most important functions to survive in the here and now, while the neocortex, being the most recent appearance structure in the evolutionary line that leads to Homo sapiens, would be responsible for the most refined and complex functions.


The logic that follows this conception of the human brain is very reminiscent of a way of understanding evolution as a process in which the new is accumulating on the old , so that these two parties maintain a relative independence from each other, although they affect each other. It also reminds us of the idea that the emotional and the rational are part of two diametrically opposed psychological dimensions, and that where there is one, the other does not fit.

The parts of the brain according to Paul MacLean

Now that we have reviewed above the ideas on which the triune brain model is based, let's look at its parts separately:

1. The reptilian brain

For Paul MacLean, the concept of a reptilian complex served to define the lower zone of the forebrain , where are the so-called basal ganglia, and also areas of the brainstem and cerebellum responsible for maintaining the functions necessary for immediate survival. According to MacLean, these areas were related to the stereotyped and predictable behaviors that, according to him, define vertebrate animals that are not very evolved, such as reptiles.


This structure would be limited to making simple and impulsive behaviors appear, similar to rituals that are always repeated in the same way, depending on the physiological states of the organism: fear, hunger, anger, etc. It can be understood as a part of the nervous system that limits itself to executing genetically programmed codes when the right conditions are met.

2. The limbic brain

The limbic system, which according to MacLean appeared with the most primitive mammals and based on the reptilian complex, was presented as a structure responsible for the appearance of emotions associated with each of the experiences that are lived .

Its usefulness has to do with learning. If a behavior produces pleasant emotions, we tend to repeat it or try to change our environment so that it occurs again, while if it produces pain we will remember that experience and avoid having to experience it again. Thus, this component would play a fundamental role in processes such as classical conditioning or operant conditioning.

3. The neocortex

For MacLean, the neocortex was the most recent evolutionary milestone in the development of our brain . In this very complex structure lay the ability to learn all the nuances of reality and to draw the most complicated and original plans and strategies. If the reptilian complex was based on the repetition of processes entirely by the biology itself, the neocortex was permeable to all kinds of subtleties coming from the environment and the analysis of our own acts.

For this neuroscientist, the neocortex could be considered the seat of rationality in our nervous system , since it allows us the appearance of systematic and logical thinking, which exists independently of the emotions and behaviors programmed by our genetics.

The model of the three brains and marketing

The idea that we have a reptilian, a limbic and a rational brain has long seduced many people dedicated to the world of advertising, market research and marketing. The triúnico model allows to consider separately three areas of the psychological life of the people that is very easy to learn and internalize: a rational instance, another emotional and impulsive one.

This has meant that in recent decades the interest of advertising campaigns has focused on appealing to the reptilian and limbic brain, but not to the rational: the reason is that, considering that these two are more deeply rooted in our evolutionary history, they are easier to predict and, at the same time, produce more powerful purchase needs, given their importance and their hierarchical position as more important parts of the brain than the neocortex. Ads and marketing campaigns have gone from thinking of the customer as an agent who needs to be informed about the characteristics of the product to rationally decide according to their interests to try to touch the sensitive fiber of people to sell them a feeling associated with the product, more than the product itself.

And the truth is that this change of approach is considered a great success; unlike what happened in the 60s, today it is very common to seduce potential buyers without talking about the characteristics of the product or its price: simply evoking emotions or telling stories easily associated with a lifestyle that we want to make ours. To ignore the logic of functioning of the rational brain and to put the target in the emotions and the basic desires is proving so profitable that even products as expensive as perfumes or cars are promoted in that way.

MacLean's theory in the neurosciences, today

However, beyond what happens in the world of business, in neuroscience and evolutionary biology it is considered that the model of the three brains is out of phase , among other things, because it understands the development of the brain as a process of construction by "pieces" that have been mounted on each other and that execute certain tasks by themselves. Nowadays, the opposite is believed: that in brain functioning it does not matter so much the function performed by the parts of the brain on their own as the way in which they connect with each other to work together and in real time.

In addition, as far as we know, evolution is not making new components integrate over old ones, as they are, without altering them. Every time a mutation causes a trait to become generalized, alters the functioning of the body as a whole and the way in which the parts that had evolved before work, is not limited to "expanding" capabilities. That is why the idea that brain organs "in charge of the rational" are coupled with the previous ones has not been well accepted.

In addition, the functions supposedly carried out by each of the three brains define well the characteristic behavior of the groups of animals that, according to him, represent the moment of evolution in which these structures appeared. On the other hand, nowadays we know that the basal ganglia (which would be part of the reptilian brain) do not have to do with the execution of genetically programmed actions, but are associated with the realization of voluntary movements that after being very practiced, they have become automatic, such as riding a bicycle.


3 Brain Systems That Control Your Behavior: Reptilian, Limbic, Neo Cortex | Robert Sapolsky (May 2021).


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