Today, in his first speech to his staff at the Department of Housing and Urban Development, newly minted Secretary Ben Carson delivered an extemporaneous disquisition on the unparalleled marvel that is the human brain and memory. “There is nothing in this universe that even begins to compare with the human brain and what it is capable of,” he began. “Billions and billions of neurons, hundreds of billions of interconnections.” It was a tangent in a speech about how in America, anything is possible.
It was also a speech that described slaves brought to the US as “immigrants.” That’s problematic, but Carson is not an expert on slavery. He is, however, an expert on brain-type things; before entering politics Carson was a distinguished neurosurgeon.
So it’s strange how wrong his understanding of memory seems to be.
Here’s what Carson said:
It remembers everything you’ve ever seen. Everything you’ve ever heard. I could take the oldest person here, make a hole right here on the side of the head, and put some depth electrodes into their hippocampus and stimulate, and they would be able to recite back to you verbatim a book they read 60 years ago. It’s all there; it doesn’t go away. You just have to learn how to recall it. But that’s what your brain is capable of. It can process more than 2 million bits of information per second. You can’t overload it. Have you ever heard people say, “Don’t do all that, you’ll overload your brain.” You can’t overload the human brain. If you learned one new fact every second, it would take you more than 3 million years to challenge the capacity of your brain.
This is all pretty wrong.
“It’s utter nonsense,” emailed Dan Simons, a psychologist at the University of Illinois who specializes in attention and memory. “We can’t recall extended text verbatim unless we deliberately memorized it for that purpose (certainly not books we happened to read 60 years ago), you can’t trigger accurate recall of detailed memories with an electrode (and long-term memories aren’t stored in the hippocampus), we don’t store a perfect and permanent record of our experiences (it’s not all there just waiting to be probed), and you can’t just ‘learn how to recall it.’”
You already knew this. Sometimes you remember something important, and other times you don’t. Sometimes you remember things inaccurately. Two people can remember different things about the same experience.
But Carson is suggesting that the accurate memories are in there somewhere. “This is a hot button issue,” says Steve Ramirez, a neuroscientist at Harvard. “Do we form memories and do they always stick there? Or are there certain things that we forget and they’re just kind of lost forever?”
The prevailing hypothesis is that the brain actually does both, encoding some things but not others. The ones that stick around tend to be the salient ones, the ones that hurt, that made an imprint. People don’t naturally store everything that happens because it takes energy to make a memory, so the brain seems to prioritize things with emotional color. The boring stuff like where you put your phone gets pared away.
Yeah, but what about the electrode thing? “To say that you could do that assumes that you know where you could actually find those memories, which we don’t know how to do,” Ramirez says. There are a lot of different kinds of memories—how to ride a bike versus your phone number versus where you were when you heard about 9/11—and while some of them hang out in a part of the brain called the hippocampus, the really permanent stuff seems not to rely on the hippocampus at all. That’s why people like Patient HM, a famous subject of memory research who had most of his hippocampus removed when he was a young man, could remember a lot of stuff about his childhood.
In a few cases, neurosurgeons have managed to get a patient to recall a memory by zapping the hippocampus with an electrode, but they can’t control it the way Carson suggests—if the memory of page 47 of Hamlet is even in there. “We’re barely able to activate fear or pleasure in an animal, let alone one among the constellation of memories that humans actually have,” Ramirez says.
Even if scientists could do it, they might not be getting an accurate memory. “Memory isn’t a videotape library. It’s a dynamic, adaptive system,” says John Coley, a cognitive scientist at Northeastern. “The way we encode and recall memories changes them. It may be ‘in there,’ but unless you use it, it can go away, and the way you use it can change it.”
Which brings us to Carson’s third point. Can the brain be overloaded? It’s sort of a squishy question, but we can assume he’s talking about the brain running out of space to store information, or not being able to process new information. Here, Carson has a point. Cognitive scientists agree that long term memory has an effectively unlimited capacity, but the brain’s processing power is indeed finite.
The human brain tries to sort information precisely to avoid that kind of overloading. That’s great, until it isn’t. Cognitive biases, such as when people tend to remember things that are more specific or assume something is true because they’ve heard about it a lot, exist primarily to help your brain avoid having to compute too much.
In 60 years, you probably won’t remember this article. You might not remember Ben Carson. But remember this: The brain is a lot more complex than one speech has room for.