You only use 10% of your brain (and other common scientific myths debunked)

Many popular thoughts and beliefs are circulated throughout our society, such as, "You only use 10% of your brain." But how true are these common statements? The answer is, "Not true at all." Today I'm going to take you through three examples of prevalent scientific myths and walk you through the science of why these are indeed myths and not evidence based facts!

1.) You only use 10% of your brain. One of the most common phrases I hear is the old, "You only use 10% of your brain."  Where did this myth begin? There's actually not a definitive answer to the origin of this myth, though some seem to believe it started because of a misinterpretation of a quote by philosopher and psychologist, William James who wrote, "We are making use of only a small part of our possible mental and physical resources." No matter the origin, this misconception is one that has withstood the test of time and continues to be stated as fact. But what does science have to say about how much of our brain we use?


Let's think for a minute about just a few of the activities you are doing right now. Right now you're reading this blog. This engages many different regions of your brain including the visual cortex and Broca's area, which is a region of the frontal cortex important for language comprehension. You're also breathing without even thinking about it, which is regulated by neurons in regions of the hindbrain called the pons and medulla. You'll hopefully remember a little bit of what you're reading and memory formation occurs in the region of the brain called the hippocampus. Maybe what you're reading triggers you to remember something you learned a long time ago. This process involves both the hippocampus and the cortex, which is where older memories are believed to be stored. These are only a few of the activities you're doing and we've now seen six regions of the brain that are active all at once. You're probably also hearing different sounds wherever you happen to be. I hear dogs barking outside and music playing from my computer. Hearing involves the activity of the auditory cortex. Naming only these few regions is an over-simplification of the very complex processes taking place throughout your brain at this very moment. 

It's commonly thought that brain activity translates to the cells of the brain that are "firing" or sending action potentials (the electrical signal sent from one cell to another). However, activity of the brain could also include the cells that are receiving electrical and chemical signals! There is an extraordinary amount of activity taking place in the brain just in a single moment such as this one. If you add up all the moments of the day then the brain is amazingly active. Even when it seems we are doing nothing there are always processes taking place supporting our breathing, unconscious movements, thoughts, and sensory experiences.

2.) Vaccines cause autism. Perhaps the most difficult myth for medical practitioners to disseminate is the myth that vaccines cause autism, followed by a powerful and dangerous anti-vaxxer movement. Where did the idea that vaccines lead to autism come from? Unfortunately, this myth arose when a gastroenterologist by the name of Andrew Wakefield, published a paper in the journal Lancet titled, "Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children." To understand the gravity of the claims in this publication, as well as the grave conflict of interest of Wakefield, I'm going to explain a little bit about research integrity. Scientists undergo extensive training in what is called Responsible Conduct of Research, or RCR for short. This training discusses topics like controlled experimental design, ways of removing bias (conducting double blinded experiments, for example), data fabrication (making up data), falsifying data (manipulating equipment, omitting data, etc.), and so on. These courses are intended to ensure integrity in scientific research and discuss the broader implications of research fraud for medicine and society. Actually, in the most recent RCR course I participated in, the case of Andrew Wakefield was used as the primary example of research fraud. It turns out that Wakefield was not consistent in what data he chose to include in his published paper. Instead of publishing all of the data, he picked the data that showed a correlation between Autism Spectrum Disorder (ASD) and vaccination. Another important note to make here is that a correlation does not imply causation. Meaning, just because vaccines were correlated with ASD does not mean that vaccines cause ASD.

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Another aspect of Wakefield's study is the sample being used. In human research, the sample is the group of people chosen to represent the general population so that the results of the study can be generalized to the population as a whole. Sample size is an important component of research design at the beginning of a study to ensure you have enough people participating to make conclusive results and most accurately represent the general population. In Wakefield's study, he included a sample size of only 12 children. For perspective, meta-analyses on ASD following the Wakefield scandal have samples of thousands to tens of thousands of individuals. The sample size is extremely important for deciding statistical significance in research, meaning that a difference found in the study would actually be meaningful for the general population. Lastly, Wakefield had a significant conflict of interest that he failed to disclose. It turns out that Wakefield was receiving money from lawyers of parents whose children had developed autism. 

The truth about ASD is that it is an extremely complex developmental disorder that is still under significant investigation.  There is no known definitive cause of autism at this point, but it has a strong genetic component and likely arises from interactions between genes and environment, which is the case for many neurological and psychiatric disorders. To sum up, the claim that vaccines cause autism isn't just a myth, the claim is completely false and based on scientific misconduct. Vaccines do not cause autism.

3.) Left vs. Right Brain dominance. We tend to believe that the different sides of the brain are responsible for different attributes of one's personality. We think that the right brain is responsible for creativity and the left brain is responsible for logic. This belief extends to characterizing creative people as right brain dominant and logical people as left brain dominant. However, this concept of left or right brain dominance is only a myth. 

The idea of functional regions for certain personality traits originated with phrenology. Phrenology attempted to correlate little bumps of the skull with different portions of the brain that were thought to be bigger than others. Therefore, if there is a region for combativeness on the phrenological map and an individual happens to have a bump on his or her skull where this combativeness area of the brain is believed to be found, then the individual would be considered aggressive. Phrenology, however, has been completely disproven. One of the greatest evidence for functional brain regions comes from the discovery of Broca's and Wernicke's areas in the brain. There regions are highly important for language and they are found in the left temporal lobe of the brain. This localization, however, doesn't extend to traits of personality, like creativity and logic. What does the science show us about the different hemispheres of the brain?

The right and left hemispheres of the brain are connected by a large bundle of fibers called the corpus callosum. This connections allows for "communication" between the two hemispheres of the brain and in healthy individuals, the two hemispheres are always communicating with one another and working together. One strong line of evidence that the left/right brain dichotomy is a myth is from hemispherectomies. A hemispherectomy is a surgical procedure in which a full hemisphere of the brain is removed, usually as a drastic form of treatment for certain types of epilepsy. It has been found that individuals who undergo these procedures have both their logical reasoning abilities and their creative capacities intact, meaning that both sides  of the brain contribute to logic and creativity. Therefore, creativity and logic are not confined to specific sides of the brain, eliminating the idea of a left- or right-brain dominance.


Kandel, ER., Schwartz, JH., Jessell, TM., Siegelbaum, SA., Hudspeth, AJ. Principles of Neural Science. Fifth Edition. New York: McGraw-Hill Companies. c2013

MMR and autism: further evidence against a causal association.

The Left-Brain vs. Right-Brain Myth

Bree Watkins