Humans possess remarkable cognitive faculties, characterized by abstract thinking, particularly advanced capability expressional ability and a talent for solving complex problems, exceeding other animals in these abilities. These abilities, alongside many others, are the basis on which human civilization arose in our world. The source of our unique intellectual abilities is primarily the human brain.
The brain receives messages and signals for sensory organs in our body, transmits signals and controls all of the body’s systems. Its importance is also illustrated by the fact that though its mass accounts for a mere two percent of our body mass, the brain consumes about one-fifth of the energy our body produces. Thus, it is no wonder that the human brain draws great interest and we mention it repeatedly in debates regarding consciousness, memory and morality. The extensive research in the field allows us to better understand how the human brain works and how it is linked to our thinking and expressing abilities. More often than others, these insights force us to leave behind us some “common truths” about the brain, which up until recently were considered obvious.
First claim: we use only ten percent of our brain
It is not entirely known where the false belief that humans only use ten percent of their brains came from, but it is pretty clear why we find it so appealing. Think of the immense potential of talents and abilities that might be hidden within those ninety percent that are supposedly left unused. This concept might give us hope that maybe it is a blockade, which we will overcome in the future using “brain liberating” techniques, or later in our evolutionary journey. Who knows what new and exciting realms we will be able to extend human mental abilities to?
It is possible that the source of this claim is the common conception that nerve cells account for only ten percent of cells in our brain, though it is growing clear that the source of this ratio is also wrong. Another possibility is that it is related to the fact that at any given moment certain areas in the brain are more active than others. A theory from 1890 might also serve as a source for this notion. At the time, psychologists from Harvard University studied a child that was gifted with extremely high intelligence, and from his example they deduced that humans have very high mental potential and that we use only a fraction of it. It is easy to imagine how this theory grew and developed over the years, and transitioned from using our potential to using our brain itself.
Whatever the cause may be, recent functional Magnetic Resonance Imaging (fMRI) studies clearly demonstrate that both during rest and while performing focused tasks, humans use more than ten percent of their brain simultaneously, and that all parts of the brain are active to a certain degree, according to their role. Areas that are important for facial recognition, for example, will be overactive when we see people, or photos of people, while under different conditions their activity will be reduced.
Many tasks that occupy us on a daily basis require synchronized activity in multiple areas of the brain simultaneously. This means that when the activity in one area is increased, other areas that are linked to it in the same neural network will also increase their activity, which will later decrease in a synchronized manner. This dynamic activity pattern enables the transfer of information between different areas in the brain. There are also events when many parts of the brain are activated at high intensity all at once, with no synchronization. This is an example of the occurrence during epilepsy-induced seizures, when many nerve cells are activated in an uncontrolled manner, which is expressed in convulsions and loss of muscle control.
Second claim: creative people have “right brain” and logical people have “left brain”
Our brain is composed of two halves, called hemispheres, and it is custom to link analytical thinking to the left hemisphere and artistic and creative thinking to the right hemisphere. This distinction is not completely detached from reality, as indeed there are differences between the two hemispheres, but it is highly imprecise.
The human brain has areas that specialize in a certain role or enable a certain ability. For example, in the 19th century French physician, Paul Pierre Broca found that an area in the left side of the brain, which is currently named after him, fills a vital role in language formation. It was discovered that people whose Baroca area has been injured suffer from aphasia: severe impairment in the ability to speak, which in this case is expressed in difficulty in conjuring words and composing sentences with proper grammar. Damage to a near area in the left side of the brain, called Wernicke area, is the cause of a different type of aphasia. A few months ago this condition received publicity when it was revealed that the actor Bruce Willis suffers from it.
Nevertheless, understanding and forming language are highly complex activities that are not limited to Wernicke and Broca areas. Many parts of the brain take part in linguistic processing processes, and damage to any of them could result in impairments in speech, writing or comprehending language. Though a significant part of linguistic processing does take place in the left side of the brain, it involves both hemispheres to a certain degree.
The right side of the brain also has roles that are its expertise. For example, the prefrontal cortex is essential for deciphering emotions in facial expressions. The right dorsal anterior cingulate cortex was linked with the cerebral processing of music. The right side of the brain does not act on its own in these functions either, and it appears that both sides of the brain are necessary to invoke a proper human response.
These differences and others like them brought on the belief that in people with artistic tendencies, the right side of the brain is dominant, while people who have an analytic nature make more use of the left side of their brain. In a 2013 study, researchers attempted to directly examine the claim that there are people that one side of their brain is stronger than the other. To this purpose, they used an fMRI to scan the brains of over one thousand subjects, between the ages of 7-29 and examined their activity during rest. The findings did not present any evidence for the existence of a tendency for right nor left brain activity. While there are brain functions that are more related to a certain hemisphere, it is not enough to conclude that people have a dominant side to their brain.
Third Claim: larger brain is indicative of higher intelligence
It would seem logical to think that there is a relation between the size of the brain and the complexity of the intellect. The larger a brain is, the more nerve cells are present within it, which produces a more convoluted network of connections between them. This will probably result in increased intelligence, right?
In nature, there are many examples that disprove the existence of a simple link between brain size and intelligence. For example, the brains of elephants and whales are significantly larger than the human brain, and yet humans exhibit mental skills that far surpass them.
Another factor could be more significant than the sheer size of the brain. Studies have found a partial link between intelligence and the number and density of nerve cells in the brain, and also to the level of connectivity between the brain cells - meaning to what degree are the nerve cells connected and how much information can pass between them. So it is possible that brain size is somewhat indicative of intelligence, but you cannot conclude that it is determined by it.
It appears that many more factors take part in determining intelligence beyond brain size, and some remain unknown to us. This could be nicely illustrated by the fact that the brains of people who were considered especially smart are no larger than the average brain. For example, the brain of physicist Albert Einstein was relatively small and weighed only 1,230 grams, compared to the average male brain mass of 1,376 grams. Generally speaking, there is no solid evidence that links the difference in intelligence between people and physical qualities, like the size of their brain or body.
Fourth claim: drinking alcohol kills brain cells
Though there is no doubt that excessive alcohol consumption harms brain functions, it appears that the main and immediate damage is not in the integrity of brain cells, but in their function and the network of links between them. These links between nerve cells are called synapses, and they are the basis for communication between brain cells and the high calculation abilities of the brain. Exposure to high quantities of alcohol enhances the effect of the neural conductor GABA, for example, which delays the transfer of messages between nerve cells. In the long run, the cells that sense the enhanced GABA effect will decrease their sensitivity to it, and result in experience of stress and irritation.
And yet, excessive alcohol consumption might result in irreversible brain damage and a reduction in the volume of certain brain areas. So it appears that alcohol does lead eventually to the death of nerve cells, though indirectly and not at once. The cells die as a secondary effect of the damage done by prolonged alcohol consumption, like increased production of free radicals and induction of inflammatory response. Additionally, alcohol has a stronger effect on brains that have not completed their development, which is why it is so dangerous for children.
Moreover, excessive alcohol consumption might result in Wernicke–Korsakoff syndrome, which impairs memory and the ability to learn new information. The syndrome is indeed caused by direct cell damage, though not in the brain but in the intestines - it impairs the intestines’ ability to absorb vitamin B1 (Thiamine) which enters the body through the digestive system. The vitamin is essential for brain function, and its deficiency might result in irreversible disruption to many important processes.
Fifth claim: serotonin is the “happiness hormone,” its deficiency causes depression
Humans are naturally inclined to catalog complex phenomena and provide simple explanations for them. Imprecise and overreaching interpretations of limited research findings might encourage people to attribute one substance with the full responsibility of complex human behavior. This is how the molecule oxytocin, which is active in the brain, received the name “love hormone”. Similarly, the neural conductor serotonin, which is related to brain functions in many areas in the central nervous system, which was once known as the “happiness hormone”
The connection between serotonin and happiness was forged due to the random discovery of this popular family of antidepressants, which also includes Prozak, and the realization that they increase the levels of serotonin in the nervous junctions in the brain. From this stemmed the notion that if serotonin is effective in alleviating depression, it means that it provides an overall improvement of the state of mind.
Today we understand that our state of mind is related to many factors and complex and dynamic processes. Thus, even if serotonin is directly related to it, in no way does it solely dictate our feeling, but functions as a component in a vast, multilayered system. We will possibly discover more valuable details regarding the roles that serotonin fills in the human brain and find more useful ways to use it. However, the hypothesis that increasing serotonin levels alone will suffice to improve a person’s state of mind has been rebutted in many studies.
Sixth claim: after puberty the brain stops developing
In the first years of a child’s life, her or his brain rapidly grows and develops. During this period we see a significant increase in brain volume and the extent of links between nerve cells. Nevertheless, during our entire lives, unwanted links between nerve cells degenerate and other links form in their place, according to the body’s activity and the input it receives from the environment. Over the years there is a significant reduction in the brain's growth and development rate, but this does not mean that it fixates at a static state and stops changing.
Our brain continues to consolidate and form new connections between nerve cells during our entire lives, even many years after we have stopped growing. New synapses are formed when we learn a new skill and have new experiences and they allow us to continue to develop all the time as thinking and learning organisms. Even at an older age constant processes of transformation continue to occur. And if that is not enough, in contrast to the popular belief the formation of new nerve cells is still possible at an advanced age, for example, in areas that are related to forming new memories.
The brain and I
Since the dawn of history, our brains have given us humans a significant advantage and enabled us to become the dominant species on earth, bend nature to our needs and settle almost everywhere on the globe. These accomplishments require immense complexity and it will take many more years of research until we are able to decipher the mysteries of the organ that defines us more than any.
It is also important to understand that the brain does not operate in a vacuum, but instead is an inseparable part of the entire fabric of our body’s systems. Thus, there is no doubt that we will encounter many more weird claims regarding the human brain. Eventually, many of them would be rebutted. A few, as sometimes happen, will be confirmed. In the meantime science will continue to fulfill its designated role: finding the truth.
- Content distributed by the Davidson Institute of Science Education