on the 'ten percent of the brain' myth

I watched a movie called Lucy, with Scarlett Johanssen and Morgan Freeman, last night. Nice science fiction flick. The first twenty minutes were particularly brilliant, but then I was sadly disappointed to hear that they made Morgan Freeman repeat that old chestnut about humans only using ten percent of their brains. I mean, come on, the man deserves more respect than that. At least he was getting paid bloody well, I suppose. 

I'm surprised that this myth has lasted so far into this day and age of MRI technology, but it is still a very popular idea, and not just in the realm of Hollywood fiction. Why is that? Why do people just accept a statement like that with no evidence, let alone common sense, attached, and go on to repeat it as truth? Is it just because it sounds catchy and profound? Apparently that is enough for many a human brain. But this is not because we only use ten percent of them. 

Firstly - where did this myth come from? There are a few different theories about when this idea first entered public awareness. The reason that there are multiple theories is that there is no evidence at all as to its origin. We don't know, for sure, who came up with this idea first, or how they came up with it. There was never any study or research or scientific inquiry of any kind that came up with these results. If there was, there would be some evidence of it in the annals of history. But nobody has ever been able to find, let alone reproduce, any such results. 

It seems that this idea really took wings after it was included in a foreword to the massively popular How to Win Friends and Influence People by Dale Carnegie in 1936. In his foreword, Lowell Thomas claimed that "Professor William James of Harvard used to say that the average man develops only ten percent of his latent mental ability." Whether he used to say this or not, we can't be sure, but there is no evidence that he ever said such a thing. There's no evidence that he wrote it, either, in spite of producing such a prodigious volume of literature that a 47-page bibliography of his works, compiled by John McDermott in 1977, was non-exhaustive. Even so, it's worth noting that this quote refers to one's 'latent mental ability', which is quite a different thing to a 'brain'.

If we don't know where this ten-percent-of-the-brain idea came from, do we know if it is true? The short answer is no, it's not true. The long answer is well, it depends on what you mean exactly by 'using the brain', but in either interpretation, no, it's still not true. 

We've had MRI technology for a long time now, which gives us clear pictures of which parts of the brain are more or less active at any given time. And so we have had clear evidence for all this time that we do use 100% of our brains. Not every part of it is active for every different activity we might be doing, but throughout a day, 100% of our brains are used at least some of the time. Even when we are asleep, large areas of our brains are very active. Sometimes, parts of our brains can be lost to injury or illness. People can survive and live functional lives with only half of their brains. But if anyone ever lost the ability to use 90% of their brains, they would be dead. There wouldn't be enough left to take care of basic autonomic functions. 

But then someone might say, oh I didn't mean it like that, I didn't mean the proportion of the physical brain that is being used. I mean, people are only using 10% of their potential capacity. Capacity for what exactly is hard to define, but it seems to be understood to align with Thomas' idea of 'latent mental ability.' The idea that we all have more potential for intellectual or neurological development seems intuitive and easy to accept, perhaps because growth is a natural function of life. And in this sense, yes, of course, we are only using a fraction of our brain's full potential. The problem here is the specific fraction, because if we are interpreting 'using the brain' to refer to this dimension of human experience, then the fraction of our potential that we can use at any given time is much, much, much less than 10%. I can't find a specific number, but it seems that it would have to be only a very small fraction of 1%. 

The human brain does indeed contain extraordinary potentials, likely many of which we will never even imagine in our lifetimes. The potential is so extremely diverse that it is impossible to do all of it. We can only do some of the things within our potential at any given time. 

Think about it. Even within the autonomic system, our brains can do all sorts of things without us even having to be consciously aware of it. It can speed our heart rate up, or slow our heart rate down. It can make us increase our body temperature, or make us decrease our body temperature. It can make us increase our metabolism, or decrease it. These are all potentials that are directly contradictory. We can't possibly do them all at the same time, or within a short period time. Even if we take out these more black-and-white examples of contradictory functions, the fact remains that within every aspect of human potential, it would be impossible for any individual to fulfill every possibility implied by that range of potential. We simply cannot do everything, or be everything, in one human body. 

There is also the idea that because successful brain function lies in neurons making connections through synapses, if we could increase our neural connectivity, we could increase our brain's capacity. No, it absolutely does not work like that. You know what happens when a brain makes more neural connections than it's supposed to? A seizure. That is literally what a seizure is. The brain opening up too much of its potential function at once, resulting in actual function being impeded. If a human brain even attempted to make even a half of one percent of its potential neural connections, which are of a number greater than the number of stars in the galaxy, it wouldn't get far at all before there was massive, fatal seizure activity. Increasing brain function beyond normal parameters does not make you smarter or more capable. It makes you disabled. 

In either interpretation, if you used 10% of your brain, you would be dead. 10% would be either nowhere near enough, or way too much, to be compatible with human survival.