The limbic system or paleomammalian brain, seat of our basic emotions and motivational circuitry and what Freud called the libido.
If one follows the evolution of the brain in higher organisms, it begins with the reptillian brain, which sits above the spinal cord and regulates basic functions like respiration and heartbeat.
Above that, one finds the paleomammalian brain, which is similar in all mammals, from mice to men. This is the area of the brain that learns from emotional experience, that means that a cat that sits on a hot stove won’t do so again.
Above and around that, one finds the neocortex, which fist evolved to process and interpret our sense impressions, identifying the class of objects known as stoves. It became the seat of our intellects, and it is what I am using to write and think about this, just as it is what you are using to read and think about it.
But our basic motivations are still determined by the limbic system, with its needs, pleasure, and pain. While the neocortex, which does our thinking and is the seat of our higher consciousness, likes to think that it’s in charge, it has only a limited ability to reprogram the paleomammalian brain — as anyone who has ever tried to stop smoking or lose weight knows.
The needs of the paleomammalian brain are so central to our survival that they ordinarily take precedence.
Consider a pattern of behavior. Typically, we receive a sensory input. That is analyzed and classified by the neocortex, which takes into account our prior experience with that class of objects and then develops a strategy to maximize pleasure and minimize pain — what Freud called the pleasure principle.
In short, it is finding a behavioral strategy to serve the needs of the motivational circuitry in the limbic system.
Behavioral strategies that have been known to produce negative emotional results, such as sitting on a hot stove, are suppressed, while those that have known to succeed, like avoiding the stove and curling up in a beam of sunlight instead, are reinforced and become our default behaviors.
That is the origin of repression, the phenomenon Freud first observed whereby the neocortex suppresses a behavior and makes it unconscious. Even trying to think about a repressed behavior makes us anxious — what Freud called the reaction formation.
This is where the neocortex begins to depart from rationality. It evolved as a tool for behavior, rather than objective analysis. It will therefore repress thoughts that cause pain to the organism, even if those thoughts are true. It will even create fantasies that mislead us, because they serve the limbic system by making us feel good. If we look in the mirror and decide that we don’t look our age, we are probably fooling ourselves because it makes us feel good, thus serving the imperatives of our motivational circuitry.
Man is a social animal, almost (though not quite) a eusocial species like bees and ants. Groups of people work cooperatively, like a single metaorganism. We have therefore evolved to internalize both the cognitions and emotions of the group, and of other members within the group. We are less individual than we think.
With the evolution of speech, humans have also taken culture, the learned behavior of a group of animals (not just humans) that is passed from one animal to another, to a high level of importance and development. We learn from one another, and are affected emotionally by the needs of the joint metaorganism. The process by which this affects our limbic system is called suggestion, and it is the mechanism that is used in hypnosis, as well as the enabling mechanism of art, which is itself a way of communicating the emotional/behavioral memes described above.
Because of this, we obtain beliefs from our parents and one another. Just as the desired behaviors in Section 2 can be irrational, so can belief. It is taken on faith, so to speak, and protected by the same defenses that protect behaviors based on experience.
Those are the main sources of human irrationality. Whether it’s believing that we are younger than we are, or believing that our society’s moral code is the one correct one, practical behavior takes precedence over objective analysis. To be objective, we must be more dedicated to the scientific truth than we are to our emotional needs. Few of us are able to do that; the so-called rational types, NT in the nomenclature of the Meyers-Briggs personality assessment, make up only 12–14% of the population. It seems to be in part a genetic characteristic, one that has gained importance as our society has become more knowledgeable and scientific. But even for NT’s, it involves work and a willingness to put the truth before what feels good.
One must challenge the very structure of one’s mind to achieve it, and few desire to do that, or even know that it is possible.