What using 10% of your brain would be like
There's been a lot of hubbub about this film Lucy and how there's some aspect of the movie where someone is using "more than 10% of their brain". I don't know anything about this movie, so I can't say for certain what they are trying to get at... but a movie called Limitless also had a similar premise of "unlocking more than 10% of your brain's power".
As any Google sleuth will find out, you use more than 10% of your brain. You actually use your entire brain, barring any brain damage.
But what would 10% of your brain actually look like? What would you be able to use?
Your brain (the human brain) is about 3 lbs (various internet sources range between 2.5 lbs and 3 lbs -- the brain in our lab weighs around 3 lbs).
On average, it is 5 inches wide (from "ear-to-ear"), 6.5 inches long (from "forehead to the back of the head"), and 3 inches tall (from "the bottom to the top").
We divide the brain many different ways -- by evolutionary characteristics (hindbrain, midbrain, forebrain/cerebral cortex); by functionality (frontal lobe, temporal lobe, parietal lobe, occipital lobe); by physical landmarks (left brain, right brain; cortical, subcortical); by specific areas (Broca's area, tempero-parietal junction, anterior cingulate cortex, etc); and manymanymany other ways.
"We only use 5%/10%/20%/X% of our brain." Nope! We use all of it.
"There's a 'learning'/'math'/'music'/'talent'/'X' part of your brain." Nope! The brain works in a network -- many areas of your brain integrate and contribute towards one (or any/all) of the experiences and actions you have in your life.
What would using only 10% be like?
If you aren't convinced and still believe the hype, let me drop some knowledge:
If we take 10% of all the dimensions we end up with:
Brain weight: 0.3 lbs
Brain dimensions: 0.5 in X 0.7 in X 0.3 in
Note: as stated in the comments, this isn't mathematically correct. But then again, the entire myth isn't correct.
If shrunk down, it would look something like this (this is completely inaccurate, but it's close.)
From this view, many neuroscientists could pick out areas that are seemingly "10%" of the surface area of your cortex. I've chosen a few to elaborate on...
If you only could use 10% of your brain, you could only use one of these two areas. Red is known as Broca's area and blue is known as Wernicke's area. Broca's area is used for speech production. If you've ever met someone who had Broca's aphasia, which is an impairment to this area, they have troubles trying to clearly verbalize what they want to say -- sometimes coming out like stutters or single words. Wernicke's area is used for speech processing, or being able to comprehend and integrate what you want to say. People with Wernicke's aphasia sometimes produce very nonsensical sentences -- their Broca's area is fine, so it sounds like a normal sentence, but the meaning is jumbled and incomprehensible. This is sometimes known as "word salad".
YOU COULDN'T DO ANYTHING ELSE. In fact, you wouldn't even be able to talk in order to make use of these speech areas (we'll get to that in a second).
If you could only use 10% of your brain, you would only be able to use a part of your cerebellum. Your cerebellum is involved with motor movements -- both fine movements (like finger-pointing or wiggling) and gross movements (like swinging your arms or walking at a pace). The part highlighted in red here could represent only being able to use fine or gross movements on the right side of your body (for many functions, your left brain will control your right side and your right brain controls the left side; this is known as contralateral control).
Again... YOU COULDN'T DO ANYTHING ELSE. Sight? You wouldn't have it. Ability to plan? Nope. Hearing? Hahahahahaha..... no.
If you only could use 10% of your brain, you could only move or feel (not both -- either/or) particular fine motor or sensory features. In this crude highlighting, I've determined you can choose to either move or have sensation through one of these combinations: hip/knee, hand/wrist/fingers, neck/eyebrow ridge/eyes, voice/lips, or tongue.
And, as mentioned before, only on one side. You want to move your hands on both sides? Sorry, that's 20% of your brain. Feel through the touch of your knee? You'll have to choose either your left or right knee.
And once again, YOU. CAN'T. DO. ANYTHING. ELSE. Again, no sight. No hearing. You would be able to vocalize noises but you have no use of Broca's and Wernicke's areas in order to produce anything meaningful. You could move one of these areas but you have no ability to walk. We haven't even discussed bodily functions or how you would be able to keep your heart beating and lungs respiring. Did you think that stuff was regulated magically by something not connected to your brain?