An enduring myth says that we only use 10% of our brains, with the other 90% standing for extra capacity.
Huxters promise to unlock this hidden potential with "neuroscience-based" methods, but what they really unlock is your wallet.
Two-thirds of the public and nearly half of science teachers mistakenly believe the 10% myth.
In the 1890s, William James, the father of American psychology, said, "Most of us do not live up to our mental potential." James meant it as a challenge, not an accusation of lack of brainpower.
But the misunderstanding stuck. Also, scientists have long been unable to figure out the purpose of our large frontal lobes or vast areas of the parietal lobe.
The damage did not cause motor or sensory deficits, so officials concluded they did nothing. For decades, these parts were called silent zones, their work was unusual.
We have since learned that they underlie executive and integrative abilities, without which, we would hardly be human.
They are important for abstract reasoning, planning, weighing decisions and flexibly adapting to situations.
The idea that 9/10ths of your brain is sitting idle in your skull makes sense when we calculate how the brain uses energy. Rat and canine brains use 5% of the body's total energy.
A monkey brain uses 10%.
An adult human brain, which is only 2% of the body's volume, uses 20% of the glucose it burns daily. In children, the figure is 50%, and in infants, 60%.
This is much larger than expected for their relative brain size, which is a scale proportional to body size. Humans weigh 1.5 kg, elephant brains 5 kg, and whale brains 9 kg, yet on a per-weight basis, humans pack in more neurons than any other species.
This dense packing is what makes us so smart. There is a trade-off between body size and the number of neurons that a primate, including us, can maintain. A 25 kg monkey needs to eat 8 hours a day to maintain a brain with 53 billion neurons.
The invention of cooking a million and a half years ago gave us a huge advantage. Cooked food is soft and pre-digested outside the body.
Our guts absorb its energy more easily.
Cooking frees up time and provides more energy than if we eat foods raw and thus we can maintain a brain with 86 billion densely packed neurons. 40% more than a monkey.
Here's how it works. Half of the calories the brain burns go toward maintaining structures just by pumping sodium and potassium ions across membranes to maintain electrical charge.
To do this, the mind has to be an energy hog.
It uses an astonishing 3.4 x 10^21 ATP molecules per minute, ATP being the body's furnace coal.
The high cost of maintaining resting potentials in all 86 billion neurons means that little energy is left to propel signals between axons and synapses, the nerve discharges that actually do the work.
Even if only a small fraction of neurons in a given region fire at any one time, the energy load of generating spikes across the entire brain will be unstable.
This is where energy efficiency comes in.
Signaling to only a small proportion of cells at any one time, called sparse coding, uses the least amount of energy, but carries the most information.
Because a small number of signals have thousands of possible paths through which to distribute themselves. One drawback of sparse coding in a large number of neurons is its cost.
Worse, if a large proportion of cells never fire, they are redundant and evolution should have killed them off long ago.
The solution is to find the maximum proportion of cells that the brain can have active at the same time. For optimal performance, between 1% and 16% of cells should be active at any given moment.
This is the range of energy we have to live with in order to be fully conscious. The need to conserve resources is because most brain operations must occur outside of consciousness.
That's why multitasking is a fool's errand.
We lack the energy to do two things at once, let alone three or five. When we try, we do everything less well than if we had focused on it.
The numbers are against us. Your mind is already smart and powerful. So powerful that it takes a lot of power to stay powerful. And so smart that it has an energy saving plan.
So don't let a fraudulent myth incriminate you about your supposed slow mind. Crime would be a waste of energy.
After all that, don't you realize that wasting mental energy is dumb?
You have billions of power-hungry neurons to maintain. So hop for it!
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