That Neuroscience Guy - The Neuroscience of Photographic Memory

Episode Date: January 28, 2024

Can people remember pictures forever after seeing them once? Are you able to recall entire pages of text you read years ago? In today's episode of That Neuroscience Guy, we discuss the evidence, or lack thereof, for photographic and eidetic memory. 

Hi, my name is Olof Kregolsen, and I'm a neuroscientist at the University of Victoria. In my spare time, I'm that neuroscience guy. Welcome to the podcast. Well, we've all seen the movies. The person with the photographic memory who can read a book, put it down, and then read pages back. They're randomly picked from memory, word for word. But is this real? Can people really have photographic memory? That's what we're going to talk about on today's podcast. Let's start with definitions.

A lot of people think that photographic memory is the same thing as eidetic memory, but that's actually not true. Although these words are used interchangeably, they actually refer to two separate things. Eidetic memory is the ability to see a visual image of an object or a place with absolute clarity after the visual stimulus is removed. For example, a vase is put on a table and a person with eidetic memory looks at it, and then the vase is suddenly removed. Now, after the vase is suddenly removed, people with eidetic memory still see the vase with absolute clarity, like it's still there. Now, we're not talking about mental imagery here. When something's in mental

imagery, you sort of have this vague image of what the thing looks like. But people with eidetic memory actually see it as if it's really there. So it's not an internal image of the vase. It's an external image as if it's actually there. Now, this image typically only lasts for minutes or even seconds, and then it fades away. But that's what happens with people with eidetic memory. They see things that are no longer there. They can hold on to that visual image. And there are a few cases of auditory eidetic memory. Now, like I've said,

it's important to note that this visual image is external. And that's different, like I've said, from mental imagery. So people with eidetic memory see the image as if it's still there. But there's a catch too. Eidetic memory is incredibly rare, and it's only found in a very small set of children, and even more rarely in adults. So this is something that's out there, but it's incredibly, incredibly rare. So this is something that's out there, but it's incredibly, incredibly rare. Now, before we talk about photographic memory, let's review memory in general. Now, we've done a podcast on this, so I'm going to keep this pretty quick,

and I guess you could go back and listen. But here's the Coles notes. Basically, if you look at the way we define memory, there are two sort of major types of memories. There are explicit memories and implicit memories. Explicit memories are external things, and we're going to come back to that. These are things that we remember about the world, and the best way to think about it is they're conscious things. These are conscious memories that we have, whereas implicit memories are internal memories or subconscious memories. And the best example of an implicit memory is a motor skill. Now we're not going to focus on implicit memories because

usually when people talk about photographic memory they're talking about explicit memories. Now explicit memories are further subdivided. There's two key types of explicit memories. There are semantic memories versus episodic memories. So semantic memories are memories about facts. So who's the president of the United States? What's the state capital? What's the tallest mountain in the world? And things like this. These are semantic memories. Episodic memories are memories of events. What happened last night? What happened on your birthday two years ago? So those are semantic versus episodic memories. Semantic memories are typically learned via repetition. This is why we study when we're in school. If you want to learn human anatomy, for instance, you need to review the anatomy of the body over and over and over

again, and repetition strengthens those semantic memories. Episodic memories, however, are typically learned in a single exposure. When you think about what you did last night, your brain doesn't need to rehearse that over and over again. It's encoded, and it's just that one exposure, and all of a sudden you have that memory. So that's explicit versus implicit memories, semantic versus episodic memories, and let's just quickly review how memory actually works. Well, when you see something, say you are trying to read a book, and this might be the case of someone with photographic memory,

well, sensory memory is basically you're reading the words as it happens, and they're held very briefly. And that passes into short-term or working memory. And that's basically where the information is held for a longer period of time. And when I did the memory podcast, you might remember the example, which is if you're introduced to a bunch of people and you know their names, but then you forget them, that's working memory. That information's held there briefly, but it doesn't go into long-term memory. We want to take stuff from short-term memory or working memory and push it into long-term memory. And modern theories say that there's another kind of memory called long-lasting memory, but we won't get into that here. Now, the key piece of how memory works, or at least one of

the key pieces for these explicit memories, is the hippocampus. And basically what the hippocampus is doing is it's binding all of the little pieces of information together. Because a memory is not just one little spot in the brain, it's distributed across the brain, and the hippocampus holds that together. And as we sleep, and as we rest throughout the day, consolidation occurs, and that's when the memory forms up and gets pushed into long-term memory. Now here's the key piece. If you have photographic memory, in principle, sensory memory would process the page you're reading, it would pass into working memory, and then it would go into long-term memory, and binding would occur, and consolidation. Now, for most of us, we know

that's hard to do. A lot of times we read things, or we see things, and we very quickly forget about them. But people with photographic memory apparently can do this, and process this, and hold on to all of it, and recall it at will. And that, of course, is the last step of memory. Recall is when you take things from long-term memory and bring them out to working memory where you could read back the words on the page, for instance. So what about photographic memory? Basically, it's tied to these semantic and episodic memories, this ability to have this perfect memory of reading a book and, you know, the words on the page or this perfect memory of something that happened a long time ago. And what seems to be the case with people with photographic memory is it's a single exposure. You know, if you and I were going to try to remember war and

peace word for word, we'd probably have to read it over and over and over again. But people with photographic memory can purportedly read this and process it with a single exposure. Now here's the rub. There's little to zero evidence that photographic memory actually exists. It's something that's an urban myth, if you will. There are no scientific studies that demonstrate the existence of photographic memory. So what is real? Well, like everything, memory is a spectrum. There are people at the top end of the spectrum, the 99th percentile, and statistically that's less than 0.1% of the population. So there are these people that have amazing memories, just like there's people that are very tall, people that are very quick, people that are slow, people that have all sorts of

differences, and some people are just naturally very good at memory. Now, why are they different? Well, there's a lot of theories about this. These people at the top end of the spectrum, perhaps their hippocampus is binding more efficiently. They just have an excellent hippocampi. Or perhaps their consolidation process is more efficient. While it takes us a lot of consolidation to firm up a memory, for these people, it happens very, very quickly. And there's a lot of examples of this.

Chess grandmasters, they are able to recall an incredible number of board positions. These people can reach back and tell you about games and recreate games that happened 50, 60, 70 years ago from memory. But what's interesting about these people is when you test them, their memory in other areas is perfectly normal. So their memory is what we call domain specific. So there are these people that have these incredible memories. They're generally not across the board. They're generally specific to a domain. And if you think of the chess example, that's probably someone that has very good memory coupled with an incredible amount of practice

remembering those games. There's actually something called the World Memory Championships, where people come every year and compete for prizes. But to date, there's been no claim from any winner of a photographic memory. They all just say that they have a good memory. Now, there are some people that have memory that you might think is photographic. A lot of autistic savants demonstrate this. And again, I've talked about this in the past, but I'll bring up the example of Stephen Wiltshire. Stephen Wiltshire is a man who basically has an incredible visual memory. And if you go on YouTube and you put in the name Stephen Wiltshire, you'll see some pretty incredible stuff. One of

the most common ones is they fly him in a helicopter over top of Rome and just once he doesn't go do laps over top of the city they just fly him over Rome once and then they take him to a room with a canvas this massive canvas that spans the walls of the room and he begins redrawing Rome from memory and what's crazy about it is he's even got like the windows and buildings that are open and closed correct so the detail is amazing now he does make a few small mistakes but all in all it's an incredible incredible display of memory and what's interesting with Stephen Wiltshire is he is an autistic savant in other areas he's he's not quite he's not as high functioning. He's got this incredible visual memory. And one of the theories about this is a lot of us, basically, when we see the world,

we decide very quickly whether we should remember it or not. And even if we want to remember it, sometimes we can't. And it's almost like in Stephen's case, he just records the whole thing. And he's able to hold on to it. But is that truly photographic memory? I'm not entirely sure, but that's about as close as it really gets. Well, there you go. Photographic memory. It doesn't exist. At least that's what scientists would tell you. All right. That's all I have for the podcast this week. Remember the website, thatneuroscienceguy.com. There's links

to our Etsy store. I've put up a bunch of, well, actually, I didn't really put up a bunch of shirts. There are a bunch of shirts that apparently had to be reconnected. So now there's more merch up there. And then there's Patreon. Thank you to those that support us that way. Basically, you sign up and money goes to the podcast. There's also, of course, ideas. We need lots of ideas for the podcast.

We want to know what you want to know about the neuroscience of daily life. Matt and I sat down the other day and we went through all of the stuff on X and threads at that neuroscience guy. We went through all the emails, that neuroscience guy at gmail.com. And we've got this massive list of ideas, but we want more. And of course, thank you so much for listening to the podcast. My name is Olaf Kurgolsen, and I'm that neuroscience guy. I'll see you soon for another neuroscience bite.