Did We Only Use 10% of our Brain?

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Did We only Use 10% of our Brain?

It is often said that humans only use 10% (sometimes 20%) of their brain. Where did this myth come from? Some say it came from Einstein, who responded once during an interview that he only used 10% of his brain. Early research on the brain may have supported this myth.

In the 1930s, Karl Lashley explored the brain using electric shocks. As many areas of the brain did not react to these shocks, Lashley concluded that these areas had no function. This is how the term “silent cortex” came into circulation. This theory is now judged to be incorrect. Dubious interpretations of the brain’s functioning have also fuelled this myth.





Today, thanks to imaging techniques, the brain can be precisely described in functional areas. Each sense corresponds to one or several primary functional areas: a primary visual area, which receives information perceived by the eye; a primary auditory area, which receives information perceived by the ear, etc.

Several regions are linked to the production and comprehension of language. They are sometimes described separately by physiologists, and the public which remembers these partial descriptions may gain the impression that the brain functions area by area. This would be consistent with the image that, at any one moment, only a small region of the brain is active but this is not what occurs.

"Understanding the Brain", The Birth of a Learning Science, 2007, page 113

In The Man There Are NOT Critical Periods To Learning

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Are There Critical Periods to Learning? (2)
In Learning: The Birds Have Critical Periods, The Man Has Sensitive Periods

The concept of "Critical Period" dates back to experiments conducted in the 1970s by the ethologist Konrad Lorenz which are relatively well-known by the general public.

He observed that fedglings on hatching became permanently attached to the prominent mobile object of the environment, usually their mother, which attachment Lorenz named as “Imprinting”. By taking the place of the mother, Lorenz managed to become attached to fledglings which followed him everywhere. The period that allows this attachment is very short (right after hatching); once in place, it was impossible to change the attachment object and the fledglings permanently followed the substitute instead of their mother. The term “Critical Period” is appropriate for such a case as an event (or its absence) during a specific period brings about an irreversible situation.



The acquisition of skills results from training and the strengthening of certain connections, but also from pruning certain others. There is a distinction that needs to be drawn between two types of synaptogenesis – the one that occurs naturally early in life and the other resulting from exposure to complex environments throughout the lifespan. Researchers refer to the first as “Experience-Expectant Learning” and to the second as “Experience-Dependent Learning”.

Grammar is learned faster and easier up to approximately age 16, while the capacity to enrich vocabulary actually improves throughout the lifespan (Neville, 2000).

Grammar gives an example of sensitive-period learning and is experience-expectant: for learning to be done without excessive difficulty, it must ideally take place in a given lapse of time (the sensitive period). Experience-Expectant Learning is thus optimal during certain periods of life.

Learning that does not depend on a sensitive period, such as the acquisition of vocabulary, is “Experience-Dependent”: when the learning best takes place is not constrained by age or time and this type of learning can even improve as the years go by.

Are there “Critical Periods” as unique phases during which certain types of learning can only successfully take place? Can certain skills or even knowledge only be acquired during relatively short “windows of opportunity” which then close once-and-for-all at a precise stage of brain development?

"Understanding the Brain", The Birth of a Learning Science, 2007, page 113

When Certain Matters Must be Learnt?

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Are There Critical Periods to Learning? (1)

When Certain Matters Must be Taught and Learnt?

The influence of the intense synaptogenesis early in life on the adult brain is not yet known, but it is known that adults are less capable of learning certain things. Anyone who starts to learn a foreign language later in life, for example, will in all likelihood always have a “foreign accent”; the virtuosity of a late learner of an instrument will in all probability never equal that of a child practised with the same musical instruction from the age of 5.

Does this mean that there are periods of life when certain tasks can no longer be learned? Or are tasks merely learned more slowly or differently at different times?

For a long time it was believed that the brain loses neurons with age, but the measures opened by new technologies have challenged this certainty. Terry and his colleagues showed that the total number of neurons in each area of the cerebral cortex is not age-dependent but only the number of “large” neurons. Nerve cells shrink, resulting in a growing number of small neurons but the aggregate number of all neurons remains the same.

Certain parts of the brain, like the hippocampus, have recently been found actually to generate new neurons throughout the lifespan. The hippocampus is, among other things, involved in spatial memory and navigation processes (Burgess and O’Keefe, 1996).

Research comparing London taxi drivers with random other citizens suggests a strong relationship between the relative size and activation of the hippocampus, on the one hand, and a good capacity for navigation, on the other; there is a positive correlation between the enlargement of the auditory cortex and the development of musical talent, as there is growth of motor areas of the brain following intense training of finger movements. In the latter case, changes in the neuron network configuration linked to the learning could be measured using brain imaging from the fifth day of training, i.e. after an extremely brief period of learning.

The processes that remodel the brain – neuron synaptogenesis, pruning, development, and modification – are grouped together under the same term: “Brain Plasticity”. Numerous studies have shown that the brain remained plastic throughout the lifespan, in terms of numbers of both neurons and synapses.

"Understanding the Brain", The Birth of a Learning Science, 2007, page 112

Everything Important Is Decided By The Age of Three?

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There Is No Time to Lose!
1st Neuromyths: "Everything Important About The Brain Is Decided By The Age of Three"

If you enter the keywords “birth to three” into a search engine on your computer, you get an impressive number of websites explaining that your child’s first three years are crucial for his/her future development and that practically everything is decided at this age. You will also find numerous commercial products prepared to stimulate your young child’s intelligence, before reaching this all-important threshold age.



Some physiological phenomena that take place during brain development can, indeed, lead to beliefs that the critical learning stages occur between birth and age three. But it can be easily exaggerated and distorted. It takes on mythical status when it is overused by certain policy makers, educators, toy manufacturers, and parents, who overwhelm their children with gymnastics for newborns and stimulating music in tape recorders and CD players attached above the baby’s bed. What are the physiological phenomena that research has uncovered which are relevant to this belief?




The basic component of information processing in the brain is the nerve cell or neuron. A human brain contains about 100 billion neurons.



Each one can be connected with thousands of others, which allows nerve information to circulate intensively and in several directions at a time. Through the connections between neurons (synapses), nerve impulses travel from one cell to another and support skill development and learning capacity. Learning is the creation of new synapses, or the strengthening or weakening of existing synapses.

Compared to an adult, the number of synapses in newborns is low. After two months of growth, the synaptic density of the brain increases exponentially and exceeds that of an adult (with a peak at ten months). There is then a steady decline until age 10, when the “adult number” of synapses is reached. A relative stabilisation then occurs. The process by which synapses are produced en masse is called synaptogenesis. The process by which synapses decline is referred to as pruning. It is a natural mechanism, necessary for growth and development.



For a long time, science believed that the maximum number of neurons was fixed at birth; unlike most other cells, neurons were not thought to regenerate and each individual would then lose neurons regularly. In the same way, following a lesion of the brain, destroyed nerve cells would not be replaced. For the past twenty years, findings have changed this view by revealing hitherto unsuspected phenomena: new neurons appear at any point in a person’s life (neurogenesis) and, in some cases at least, the number of neurons does not fluctuate throughout the lifetime.



That said, synaptogenesis is intense in the very early years of life of a human being. If learning were to be determined by the creation of new synapses – an idea with some intuitive appeal – it is a short step to deduce that it is in the early years of a child when (s)he is most capable of learning. Another version, more current in Europe, is the view that very young children must be constantly stimulated in their first two to three years in order to strengthen their learning capacities for subsequent life. In fact, these claims go well beyond the actual scientific evidence.




An experiment conducted twenty years ago may, however, have fuelled such a myth. Laboratory studies with rodents showed that synaptic density could increase when the subjects were placed in a complex environment, defined in this case as a cage with other rodents and various objects to explore. When these rats were subsequently tested on a maze learning test, they performed better and faster than other rats belonging to a control group and living in “poor” or “isolated” environments (Diamond, 2001). The conclusion was that rats living in “enriched” environments had increased synaptic density and were thus better able to perform the learning task.



The elements were in place to create a myth: a great experiment, rather easy to understand even if difficult to perform, and findings that project the expected outcome.



The experiment, however, took place in the laboratory in highly artificial conditions.It was conducted on rodents. Non-specialists twisted experimental data on rats, obtained with unquestionable scientific precision, and combined it with current ideas concerning human development to conclude that educational intervention, to be more effective, should be co-ordinated with synaptogenesis.

Alternatively, they suggested that, “enriched environments” save synapses from pruning during infancy, or even create new synapses, and thereby contribute to greater intelligence and higher learning capacity. This is a case of using facts established in a valid study to extrapolate conclusions that go well beyond the original evidence.


The limits and lessons in this case are rather clear. There is little human neuroscientific data on the predictive relationship between synaptic density early in life and improved learning capacity. Similarly, little is available regarding the predictive relationship between the synaptic densities of children and adults. There is no direct neuroscientific evidence, for either animals or humans, linking adult synaptic density to greater learning capacity. All of this does not mean that the plasticity of the brain, and synaptogenesis in particular, might not bear some relation to learning but, on the strength of available evidence, the assumptions made in identifying such a determining role for birth-to-three development cannot be sustained.




For further reading, the reader should consult John Bruer’s "The Myth of the First Three Years" (2000). He was the first systematically to contest this myth, which he presented as “rooted in our cultural beliefs about children and childhood, our fascination with the mind-brain, and our perennial need to find reassuring answers to troubling questions”.

Bruer goes back to the 18th century to find its origin: it was already believed that a mother’s education was the most powerful force to map out the life and fate of a child; successful children were those who had interacted “well” with their family. He eliminates one by one the myths based on faulty interpretations of early synaptogenesis.

"Understanding the Brain", The Birth of a Learning Science, 2007, pages 111 - 112

What is a “neuromyth”?

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What is a “Neuromyth”?

Science advances through trial and error. Theories are constructed on the basis of observation which other phenomena come to confirm, modify, or refute: another theory, complementary or contradictory to the previous one, is then created, and so the process continues.

This bumpy advance of science is unavoidable but it has its drawbacks. One is that hypotheses which have been invalidated nevertheless leave traces and if these have captured a wider imagination, “myths” take root. These beliefs may have been demolished by science but they prove to be stubbornly persistent and passed on through various media into the public mind.



Neuroscience is inevitably caught up in this phenomenon. Some expressions in the English language confirm this: “number sense”, for example, derives from the research of a German anatomist and physiologist, Franz Joseph Gall (1758-1828). By examining the heads of convicted living criminals and dissecting the brains of deceased ones, Gall established phrenology theory: a particular talent would produce an outgrowth on the brain which pushes on the bone and distorts the skull. By feeling the head, Gall boasted that he could identify the criminal from the honest man, a “maths” person from a “literary” one.

Phrenology has long been superseded, indeed discredited. To be sure, certain areas of the brain are specialised more than others with certain functions. But, contrary to the regions that Gall thought he had identified, it is instead a question of functional specialties (such as image formation, word production, tactile sensibility, etc.) and not of moral characteristics like kindness, combativeness, etc.(1)



Science itself is not solely responsible for the emergence of such myths. It is often difficult to understand all the subtleties of a study’s findings, still more its protocols and methodological details. Nevertheless, human nature is often content with – even takes delight in – quick, simple, and unequivocal explanations. This inevitably leads to faulty interpretations, questionable extrapolations, and, more generally, the genesis of false ideas.

In the next posts, we examines one by one the main myths belonging to brain science, with particular attention given to those most relevant to learning methods. For each myth, a historical look will explain how the idea took hold and then the current state of scientific research on the subject will be reviewed. Ironically perhaps, some myths have actually been beneficial to education in that they provided “justification” for it to diversify. But, mostly they bring unfortunate consequences and must therefore be dispelled.

"Understanding the Brain", The Birth of a Learning Science, 2007, page 110

See Dispelling “Neuromyths” in this blog.