Photo by Gage Skidmore
As every neuroscientist can tell you, most people don’t understand the difference between neuroscientists, neurosurgeons, and neurologists.
Neurologist: A medical doctor who diagnoses and treats diseases of the nervous system
Neurosurgeon: A medical doctor who slices your brain up in order to heal it
Neuroscientist: A scientist who studies how the nervous systems of all animals work. Most work at a level so abstract it seems pointless (but it isn’t!)
What does this mean? A neurologist listens to your symptoms and will try to figure out what has gone wrong in your brain; a neuroscientist tries to understand how the brain and nervous system work down to the finest detail, no matter how useless-seeming that detail might be; a neurosurgeon specializes in performing very technically challenging surgical procedures to cure disorders of the nervous system.
Ben Carson, a neurosurgeon and presidential candidate, published a tweet showcasing what he knows about neuroscience:
…the brain can process two million bits of information per second. It remembers everything you’ve ever seen, everything you’ve ever heard…
This is, if not wrong, then just plain old made up.
Let’s break this down:
“the brain can process two million bits of information per second”
Now two million bits per second certainly sounds like a lot! 2 million bits is what you might know as 2 megabits or roughly 200 kilobytes. For comparison, here is a picture of a Corgi in a Mario costume that is a little more than 200KB:
Is that too much information for you? Does it blow your mind??
It is actually really hard to calculate how much information a nervous system is ‘processing’. In fact, I can only find one paper that even attempts to answer a small part of that question: how much does the eye tell the brain? By recording from neurons in the retina, these scientists were able to estimate that one retina will transmit ~800KB/sec. This may be a bit of an overstatement [see (1) below for discussion], but obviously – the visual system is transmitting a lot of information.
But your eye is not the only thing that transmits information to the brain! You have ears, you can touch, you can sense how hungry you are or how sick you feel. All the while you are making decisions and thinking about the past and the future. Your brain is computing a lot.
In other words, while it may seem at first like ‘the brain can process two million bits of information per second’ is an overstatement, it is actually an understatement. And probably by a lot. But more importantly: we don’t know, we don’t have any clue or guess, and I have no idea where Ben Carson pulled this number from. It is plain old made up.
“It remembers everything you’ve ever seen, everything you’ve ever heard”
This makes everyone sound a bit like Santa Claus! In reality, what we know points in the opposite direction. Although it is popular to describe the brain as a computer, it is not. From the moment of perception, the brain begins by filtering filtering filtering. Your eye receives a barrage of light – and much of this is filtered away. This image gets sent to the brain – and much of this is filtered away. Your mind does its best to infer what is occurring in the world – and in the process, much is filtered away or simply assumed. It is tragically easy to force someone to perceive something that is not there. In other words, right now you cannot remember everything that you saw two seconds ago! It is simply not available to your conscious mind.
But we can be a little generous – what about memories? Could we at least recall everything we consciously perceived? Everyone knows that is not true: who can remember being a baby? And even as adults we do not remember everything. Memories are not just photos to be peered at; they are a dense connection of associations. These associations can be activated together, but always in the context of whatever else going on in the brain (and this is not even getting into totally false memories).
This is a particular problem with eyewitness testimony. It is pretty well-known at this point that eyewitness memory is unreliable and prone to manipulation. Simply asking a witness to describe someone seems to modify the memory – leaving the original gone forever.
The Inside Out view of memory as a discrete collection of little movies is wrong – though even in this movie they know that we can forget things forever! – and is based on an incorrect view of how the brain works. Memories are not crystalline balls ready to be sent up to consciousness at any moment, but a web of connections that can easily be rewired. Based on what we know about learning and memory, Ben Carson’s quote is wrong, and almost certainly made up.
From everything we know, Ben Carson is a phenomenal neurosurgeon. But Ben Carson is not a neuroscientist.
(1) How much information can the nervous system process? This is a really interesting question! It may seem straightforward, but this question actually has a lot of different interpretations. Let’s just take the example of our two eyes, each looking out onto the world. The eyes do not see totally different parts of the world, but an overlapping scene; just close each eye in succession and you will see much of the world the same.
In a sense, this means they are processing the same information about the world. Both can see the laptop (or phone/etc) in front of you and so much of what they see is redundant. If the left eye sees, say, 1MB of visual information, and the other does as well, does that mean the two eyes are processing 2MB of information? Or are they simply processing 1.25MB in parallel (the other 0.75 MB being the same thing in each eye – redundant overall)?