Stephen Wiltshire is a celebrated artist, known for his breathtakingly detailed depictions of iconic cities and skylines. What makes his amazingly elaborate and accurate hand-drawn cityscapes all the more impressive is the fact that Wiltshire creates them entirely from memory.
After essentially one look at the panorama of the city, he renders it in pencil or paint.
This has led many to insist that Wiltshire has a photographic memory. A reasonable conclusion, especially in this particular context.
Just one problem. According to established science, there’s no such thing as a photographic memory.
Camera trouble
A photographic memory is generally assumed to be the ability to remember, well, everything. If you’ve perceived or experienced something, you can remember it, no matter how much later, with 100 per cent accuracy.
Say you were in a coffee shop, at 10:16am on 9 May 2007, when a stranger sat beside you, reading a book.
An unremarkable event, sure, but if you had a photographic memory, you could still, nearly two decades later, recall it with perfect clarity, and in such fine detail that you could ‘read’ that stranger’s book, purely from the image of its pages stored and recreated in your memory.
It would be as if your brain had taken a photograph of the scene. An extremely high-resolution, panoramic photograph of everything you experience. So you never forget anything.
This scenario may sound far-fetched, but many believe it to be feasible. Indeed, in 2017, neurosurgeon Dr Ben Carson, the US Housing and Urban Development (HUD) secretary during the first Trump administration, seemed to claim that we all remember such crystal clear images of the past.
“[Your brain] remembers everything you’ve ever seen. Everything you’ve ever heard,” he said in a speech to staff.
“I could take the oldest person here, make a little 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.”
However, there remains no official record or observation of any human ever displaying such a facility with memory. In fact, what we understand about how the brain works suggests it shouldn’t be neurologically possible. Impressive as our grey matter is, it’s not that formidable.
Memories are made of this
A true photographic memory would suggest a neurological memory system that absorbs all the information that enters our brain, with 100 per cent efficiency and accuracy. It would store it with zero loss or distortion, for every waking moment, for 70 years straight (on average).
This would be a remarkable feat for the most advanced technological recording device. But something as organic, messy, and chaotic as the human brain is rarely so ordered and efficient.
Case in point: our brains don’t have one single all-encompassing memory system. There are actually several qualitatively different processes in our brain, working together (more or less) to produce the neurological patchwork quilt we regard as our memory.
There’s short-term and long-term memory. The former is essentially the buffer in our brain that holds the things we’re currently thinking about, sustained via patterns of activity in specialised neurons within our frontal lobes.
Much of the information in the short-term memory is phonological (words, our ‘internal narrative’), but research suggests there’s also a separate short-term memory buffer for shapes and images too. This is often termed the ‘visuospatial sketchpad’.
Meanwhile, long-term memory is information that’s been stored in the brain, physically, in the form of synaptic connections between relevant neurons, usually in the temporal lobe.
Long-term memory is made up of various subtypes. Some are implicit, or unconscious memories, which influence our actions and decisions, without us being consciously aware of them.
They include habits, learned emotional reactions, and procedural or ‘muscle’ memory, which is the memory for physical skills and learned abilities.
The most famous example of the latter would be riding a bicycle. Learning to ride a bike can be a complex and lengthy process, but once you’ve done it, it’s locked in.
Regardless of how long it’s been since you last rode a bike, you don’t think “Where do my feet go? How do I balance?” Your brain and body just know what to do.
Then there are explicit, or declarative, memories, the ones we are consciously aware of recalling. These can also be subdivided into semantic, or episodic, aka autobiographical, memories.
Semantic memories are those for abstract information, divorced from the context in which the information was obtained.
Meanwhile, autobiographical memories, as the name suggests, are memories of specific experiences from our lives, events perceived via our own perspectives.
So, the knowledge that Munich is a city in Germany would be a semantic memory. Remembering your visit to Munich as part of a school student exchange would be an autobiographical memory.
For a long-term memory to be viable, it must successfully undergo several processes.
First, it must be encoded, where aspects such as sights and sounds are translated into information the brain can store.
Then there is storage, where the memory is laid down in the brain in a safe, sustainable and accessible location.
Finally, there is retrieval, where the memory is located and activated as part of some cognitive process.
Basically, the brain’s memory system is a sophisticated, multifaceted setup, involving many crucial, but complex and neurologically demanding steps.
As a result, the human memory system is fallible and prone to error, as anyone who’s forgotten someone’s name within seconds of hearing it will know.
That it could successfully store absolutely everything we experience, with 100 per cent clarity, accuracy, and in fine detail, is extremely unlikely.
Misremembering
However implausible it is, even if a human brain could somehow store absolutely every bit of information that enters it, true photographic memory would require all these memories to remain intact, unchanged, for the remainder of its life. Perfect recall logically requires access to perfect information.
Again, this isn’t how memory works in our brains. Unsettling as it may seem, our long-term memories are constantly being tweaked, updated, overruled, and even removed.
For instance, we can only see the world from our own subjective point of view, and our own thoughts and feelings are the only ones that shape our memories. Emotion in particular plays a key role in memory formation and recall.
One result of this is that we have many egocentric biases affecting our memory. This means we tend to remember events in a more self-flattering form than was actually the case.
A prominent example of this is Watergate whistleblower John Dean, one of the first to come forward and expose the scandal and the Nixon administration’s illegal acts. In his testimony, he confessed to being a key player.
However, when the recordings of the meetings Dean reported were later found, they revealed that he played a much less prominent role in the events than his testimony described.
Dean had no logical reason to lie about his involvement in a major criminal endeavour in a way that made him appear more guilty.
His own memory system just couldn’t resist making him the main character in the proceedings, rather than a background extra.
John Dean was not, insofar as we know, an anomaly. This is just something that happens in a typical brain’s memory system.
Our long-term memories are also changing long after their initial formation.
The fading-affect bias means the negative emotional qualities of memories fade away, and much faster than positive emotional associations. Time really does heal (psychological) wounds, giving us an overly rosy memory of childhood as we get older.
Established memories are also often updated, or ‘reconsolidated’, as we learn new information and experience new things. After all, we live in an ever-changing world, and strictly adhering to older, outdated memories is not a good survival strategy.
And while some may believe everything we experience is stored in our brain somewhere, recent research suggests that active forgetting, the constant physical removal of unused memories, is an important process in keeping our brains healthy and functional.
It’s like how we clear out old files on our hard drive to free up space, and better organise our desktop.
All in all, the limitations of our brains make a photographic memory largely implausible.
But this isn’t to say that there aren’t certain individuals who challenge these supposed limitations.
Read more:
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- Aphantasia: What it's like to live with no mind's eye
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Forget-me-nots
The human brain is incredibly variable. It’s what makes studying it so fascinating, but also so challenging, because there tend to be exceptions to every ‘rule’. This applies to our understanding of memory, too.
The terms ‘eidetic’ memory and photographic memory are often used interchangeably. But they actually mean different things.
For one, eidetic memory does seem to exist. Eidetic memory refers to a greatly enhanced ability to recall visual (usually) information, in terms of both detail and duration.
An eidetic memory of an image is supposedly the same equivalent of looking at a photo of it (hence the overlap with photographic memory, presumably).
While it’s typically only found in children, it would be safe to assume that the artist Stephen Wiltshire has an eidetic memory.
Then there’s autobiographical hypermnesia, or hyperthymesia. People with this rare condition have a greatly enhanced ability to recall events from their lives, in profound detail.
Then there are competitive memorisers, who actively practice and train to remember vast amounts of information, and compete in extreme memory events.
As for why certain brains would have such greatly amplified memory systems, human variation will mean some brains are simply wired differently, in a manner that can result in enhanced memory.
Neurodivergence will inevitably be a factor here. The aforementioned Stephen Wiltshire is autistic.
Intriguingly, some studies suggest that many autistic children have a larger ‘visuospatial sketchpad’ than their neurotypical peers.
This would imply a greater ability to remember and process visual information.
This can manifest as enhanced maths skills, presumably due to an increased ability to cognitively manipulate abstract information (like numbers and their arrangement), potentially to a savant level, a trait often linked to autism.
Enhanced memories are also often linked to conditions like synaesthesia and OCD.
Perhaps the atypically elevated level of sensory information involved in synaesthetic perceptions, or the exaggerated focus on typically ignorable experiences in many OCD cases, means the brains in question have much more information to work with when forming memories, making them easier to recall?
Alternatively, the underlying neurological differences that lead to these conditions could also mean that more resources are directed to the memory processing regions. There’s not enough data to provide any firm conclusions yet.
The ‘mind palace’ approach (which you may have seen in BBC’s Sherlock) is also worth considering. This tactic, also known as the method of loci, allows people to remember large amounts of complex information by assigning them to imaginary locations, like a street, house or place.
Some competitive memorisers use this method to remember lists of information.
Some autobiographical hypermnesiacs also report using similar techniques to organise their abundant memories in a similar way. This strategy presumably exploits the fact that conscious memory and spatial navigation are both products of the hippocampus.
After all, ‘memories of experiences’ and ‘mental maps of your surroundings’ both involve combining information from various sources into one coherent representation, which is what the hippocampus does.
This explains why humans are often so adept at remembering and navigating our surroundings, as demonstrated by the infamous ‘beer taxi’, the phenomenon where you consume so much alcohol you can barely speak or think, but still wake up in your own bed the next morning.
Bad memories
Unfortunately, while more reliable and capacious memory may be something many people desire, it often comes with notable drawbacks.
Autism, synaesthesia, OCD, and other conditions may be linked with enhanced memory, but those who deal with them are often keenly aware of their downsides.
Similarly, those with hypermnesia will readily attest to the negatives of a seemingly flawless autobiographical memory.
Time may heal all wounds, but that’s only in a typical human memory – if you can’t forget or move on from your vivid recollections of unpleasant past events, they retain their ability to traumatise you. Again and again and again.
Also, having to come up with strategies and methods for organising your own memories isn’t something a typical person has to do. That must be quite a time saver, at least.
It’s also worth noting that the multifaceted nature of human memory in the brain means enhanced abilities (or deficits) in one area don’t necessarily apply to others.
Famous amnesic Henry ‘Patient HM’ Molaison couldn’t form new autobiographical memories for anything in the five decades since his temporal lobes were surgically removed, but could still learn new skills and abilities, meaning his ‘muscle memory’ remained.
Similarly, those with autobiographical hypermnesia seemingly show normal, or even below-average, abilities at rote learning, retaining new semantic information.
All that hassle, and it doesn’t even help with passing exams!
Given how biologically demanding our brains are, they can be ruthlessly efficient when it comes to converting resources into functions.
The typical memory works like it does because the millions of years of evolution’s trial and error have deemed it the most practical setup.
This isn’t to say this setup can’t be changed, because as we’ve seen, it does happen.
But as finely balanced as the brain is in terms of energy and resources, increasing one aspect often means reducing or compromising others. This certainly seems to be the case with memory.
Imperfect recall
Despite the immense variability of the human brain, cases of individuals with (naturally) exceptional memories are still vanishingly rare.
This will be due, in part, to research limitations. Studying a person’s long-term memories can be a tricky process, with many practical limitations.
For instance, if you do somehow find someone who claims to remember exactly what was written on the pages of a book being read by the stranger next to them in a coffee shop 18 years ago, how do you know their memory is accurate?
Unless you were there and took detailed records of the event, there’s no way to confirm it (although this limitation may become less of an issue as more and more people build up an extensive and accessible visual record of their lives via social media).
A true photographic memory, though, is unlikely to ever develop (if you’ll pardon the pun). Exceptional memories can occur, and as the human population continues to grow, we may see even more of them. But a significantly-greater-than-average memory rarely comes without cost.
Overall, while it may not be perfect, the typical human memory is pretty impressive as it is, and it is how it is for good reason.
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