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The 10% Brain Myth - BUSTED

So how much of the brain do you think we actually use? 100%? Half of it? Maybe only 10%?

For many years, it's been widely accepted that most of us get by using just a small fraction of our brains. The myth that we generally use only one-tenth (or some other small fraction) of our brains has been misattributed to many famous scientists and historical figures, perhaps most notably Albert Einstein. And the supposed amount of gray matter that we squander has gone up and down over the decades.

In 1936, journalist Lowell Thomas wrote the preface to a best-selling self-help book, Dale Carnegie’s How to Win Friends and Influence People, in which he attributed the 10% claim to one of the most revered psychologists in history, William James. What James actually said was that he doubted the average person achieves more than about 10% of their intellectual potential.

But you don't have to be a scientist to sort this one out. Just consider how the brain works, and it's pretty clear that the 10% myth is preposterous. For example, the brain accounts for about 20% of the body's energy consumption, despite only representing 2% of its weight. It doesn’t make sense that the organ requiring the most energy would operate with such inefficiency.


FUN FACT: The human brain uses about 0.3 kilowatt hours (kWh) per day for an average adult - more than 100 times what your smartphone uses!


Also, brain cells operate on the “use it or lose it” principle. It's called synaptic pruning, and cells that aren't used shrink, die, and are ultimately discarded. So if we only used 10% of the brain, we would see large-scale degeneration before the brain fully developed around age 25.

Neuroscientist Barry Beyerstein refutes the ten percent myth in the book Mind Myths: Exploring Popular Assumptions About the Mind and Brain.

· Studies of brain damage: If 10 percent of the brain is normally used, then damage to other areas should not impair performance. Instead, there is almost no area of the brain that can be damaged without loss of abilities. Even slight damage to small areas of the brain can have profound effects.

· Brain scans: Brain scans have shown that no matter what one is doing, all brain areas are always active. Some areas are more active at any one time than others, but barring brain damage, there is no part of the brain that is absolutely not functioning. Technologies such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) reveal that even during sleep all parts of the brain show some level of activity. Only in the case of serious damage does a brain have "silent" areas.

· Energy and fuel: The brain is enormously costly to the rest of the body, in terms of oxygen and nutrient consumption. It can require up to 20 percent of the body's energy—more than any other organ—despite making up only 2 percent of the human body weight. If most of it were unnecessary, there would be a large survival advantage to humans with smaller, more efficient brains. It is also highly unlikely that a brain with so much redundant matter would have evolved in the first place; given the historical risk of death in childbirth associated with the large brain size (and therefore skull size) of humans, there would be a strong selection pressure against such a large brain size if less than half of it were needed.

· Microstructural analysis: Neuroscientists are able to insert a tiny electrode into the brain to monitor the activity of a single cell. If most cells were unused, then this technique would have revealed that.

While we definitely use much more than 10% of our brain most of the time, using the entire brain wouldn’t be healthy either. Such a massive amount of electrical impulses firing simultaneously and continuously would almost certainly overload the circuitry and trigger a seizure.

The bottom line is that, while it's true that all regions of the brain are not active for every task, most are active throughout the day even during periods of sleep and rest. Thus, large portions of the brain are never truly inactive. We generally use as much of our brain as reasonably possible through the DMN, or the default mode network, a widespread brain network that is active and synchronized active even during passive rest and mind-wandering. Thus, large portions of the brain are never truly inactive.


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