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According to multiple reputable sources, the idea of "photographic memory" in humans is a myth. While some people may be unusually adept at certain things involving memory - like remembering the layout of a chess board, or where any given card is within the deck - no one can actually recall images of everything they see with perfect accuracy.


Here's my criteria for "an organism with photographic memory":

Must's

  • Organism must be organic (not a robot being called an "organism")
  • Organism must be natural (no creation of a new species by an advanced race, etc)
  • Organism must be able to recall events it has witnessed in the exact detail they were witnessed in
  • Answers should be relatively

Must Not's

  • Memories must not fade (they have to be re-callable years later)
  • Memories must not change over time (as human memories may after multiple recollections)

Up to you

  • The level of "intelligence" - there is no need for complex emotions or language, although that might be nice
  • The sensory methods of the organism - if it can't "see" in exchange for "photographic" echolocation, go for it

Noting the above criteria, can an organism evolve perfect photographic memory? If so, how would it do so? And if not, why?

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    $\begingroup$ I have taught autistic kids with total recall, but cannot say how long they remembered. I had one student with 140 sight words.and I had to replace one card.Suddenly he could not read that card, same card stock, same font... he had memorised 140 cards but to my surprise, could not read one word unless it was on the specific card. What he was learning was not what I meant to teach and was truly amazing. $\endgroup$ – WRX Dec 2 '16 at 2:39
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    $\begingroup$ Elephant never forget nor forgive... mouse prank #364 nearly concluded my findings need to find one more mouse tomorrow. $\endgroup$ – user6760 Dec 2 '16 at 8:04
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    $\begingroup$ It might develop $\endgroup$ – JDługosz Dec 2 '16 at 10:42
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    $\begingroup$ @WillowRex when my neice was very young, pre literate, she could tell which VHS tape was which by identifying its exact appearance. $\endgroup$ – JDługosz Dec 2 '16 at 10:45
  • $\begingroup$ I had a student who was able to repeat entire TV shows. It was horrible, A student teacher innocently ask him to "come on down" from a table top, and the child started self abusing as he repeated 4 hours of programs. I assume verbatim. $\endgroup$ – WRX Dec 3 '16 at 0:43
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I fail to see how such ability would evolve in a biological organism as we know it. I will first make very crude analogy between computers and organisms to argue that simply storing that information would be very difficult. Consider that one is to store the level of happiness of the organism itself every second. This would mean storing a bit of information (1/0, happy/sad) every second for the duration of the life of the organism. During one year, and in computer terms, this would equal to roughly 3.8 Mb. Over a human life this would be roughly 300Mb. Using DNA, as suggested before me, this would take approximately 5 human DNA molecules to store. To recall an event perfectly, you would need to store much much more information.

Storing all this information in DNA would however, not be possible. Firstly, growing DNA molecule (as we know it) would make copying and reading it increasingly slower. This would mean that towards the end of the life of the organism its cell division (as we know it) would slow down. This would also slow down all aspects of life of the organism. (Side note, this would of course open various interesting plot options with old individuals turning into "oracles" that are only able to lie down being fed and treated by others but do know every single thing they have ever seen/read/heard). This slowdown would also affect the process of recalling these memories in the first place. In addition, storing memories in the DNA would require the infomation be added to the molecule simultaneously everywhere in the body.

Storing this information in the "brain" of the organism would also be problematic. The structure of the brain would have to be completely different, more computer like, than our brain. Notice, that we do not necessarily learn to remember every single detail but rather associate things and memories. This is also the fundamental way our brain works. But note also, that storing an indefinite amount of data would require indefinitely large brain. Our brain, for example, consists of finitely many synapses. Such network is only able to represent a finitely complex set of information.

After the technical difficulties we come to my next point, evolving such ability. Clearly, if we consider evolution as we know it there would need to be evolutionary pressure for the nature to prefer such trait. Something in the environment of the organisms allows individuals with a very good and accurate memory to live longer or to have more/healthier offspring. Possibly, finding food, shelter or mating locations are few and far between and difficult to find. Remembering, for example, the how to find these locations could be useful enough to cause evolutionary pressure.

Such memory has a lot to do with the intelligence of the creature. The way you describe the ability suggests that the organism is able to comprehend this information (recall memories and act upon them). The organism has to be also smart enough to filter all these stored memories from each other and choose the most relevant (from possibly a massive set) to base its decisions on. Consequently, from the evolution point of view, the organism would have to evolve simultaneously smarter and better in remembering. At some point in during the evolutionary process the organism is completely capable to manage with less than perfect memory.

If we compare this to us homo sapiens, we see that currently we are rather smart but have not perfect but very well functioning memory. But by being smart enough we have essentially taken the initiative from nature and there is hardly any evolutionary pressure left on us. If your organism would reach similar situation, the evolutionary steps to create ever better memory would be removed. Essentially, if you want to evolve such organism having better memory has to be increasingly important. Usually in real world, however, adding complexity brings in a phenomenon called diminishing returns. In this context, as the brains of the organism allows more and more information to be stored, adding "memory locations" becomes more and more costly (in regards of energy consumption, volume!, and the length of the evolutionary process).

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  • $\begingroup$ We wouldn't need 300 MB of data regarding Happy or Sad alone for an average human lifetime. That is heavily unoptimized and extremely redundant. In computer terms, our brain would use Pointers. The memory would not have an emotion associated with it, but instead a little thing that says "go here to get the emotion", and "here" would be a complicated memory of happiness. Its through methods like this that our brain is estimated to be capable of storing Petabytes of data (millions of Gigabytes), or 100s of years of video. Why it doesn't, no one knows. $\endgroup$ – Ryan Dec 2 '16 at 17:01
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    $\begingroup$ A pointer (really, an address reference) is a much larger amount of data than a single "yes or no" value. The "yes or no" concept is really as compact as uncompressed data as you can get. If you want to optimize, look at compression algorithms. Simplest would be run-length encoding. "I was happy for a minute, I was sad for a second, I was happy for an hour." There are better lossless compression algorithms, but none can result in smaller output for every possible input. So the problem of needing an indefinitely-large data store for an indefinite amount of data remains. $\endgroup$ – Michael Mol May 18 '17 at 13:25
  • $\begingroup$ Human long-term memory is configured like bookends - we remember the first time, the last time, and a small number of specific interesting points in between. The nearest analogy I have is something akin to Huffman coding, but unlike Huffman coding human memory is lossy (like JPEG). $\endgroup$ – pojo-guy Dec 30 '18 at 2:50
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What if an organism evolved to incorporate into its DNA the memories of its experiences. The organism would grow "normally", but instead of simple replication of DNA, this organism would incorporate small changes into its DNA, representing its ongoing life experiences. It could reference these changes and interpret them as records for each event it has ever experienced.

This organism would meet your criteria and be plausible as well.

As Tommi Scisso suggests there would have to be some selection pressure for this attribute to evolve. It may be argued that Humans store records of all they experience, but are not conscious of them. Instead evolving a subconscious to react automatically.

Perhaps an organism could evolve to use only conscious memory. Humans remember things for survival. The conscious mind handles rapidly changing events while the subconscious is useful with mundane/repetitive/banal/understood tasks. If an organism evolved in an environment where rapid change, based on previous states, was a constant, maybe the subconscious doesn't evolve. Maybe only the conscious mind is useful and thus only it evolves.

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  • $\begingroup$ Interesting idea, but could it evolve naturally? $\endgroup$ – Zxyrra Dec 2 '16 at 12:07
  • $\begingroup$ I added a scenario to my original post where something like this might evolve naturally. $\endgroup$ – grldsndrs Dec 2 '16 at 13:19
  • $\begingroup$ This is creative but I'm afraid I cannot accept it as-is. DNA may be able to carry some detailed information, but adding to that not just descriptors of an organism but also what an environment looks, sounds, smells, tastes, feels like is an insane amount. $\endgroup$ – Zxyrra Dec 11 '16 at 5:07
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For anything to evolve naturally, i.e. becoming an inheritable trait, it should provide an advantage for the individual member of the (original) species, and must not (overly) hinder it's chance for procreation.

A memory is highly advantageous: being able to remember where that tasty food was helps spending less energy on acquiring food, meaning a net gain over other members of your species who randomly move about until they find food.

Having a better memory hels with remembering more things.

But remembering picture-perfect every single aspect of every single trip to that food source hardly brings any advantage over simply knowing that you've been there several times, and the general outcome was positive.

I think we can assume that a photographic memory will require more ressources than a slightly more vague memory. Since most likely it won't help you gathering that much more energy to compensate for the cost, it turns out to be a net disadvantage.

While evolution in general favors local maxima, it does not exactly punish mutations that perform worse. If you think about a species in a very comfortable ecological nieche, it would be conceivable that this energy-intensive trait would still perform well enough to not hinder the individual's reproduction.
But still you will at the beginning of this evolutionary path have a few individuals sharing that trait, and unless you find any setting where this trait provides them with more successful chances at reproduction, it won't catch on, and will die out once the ecological nieche they live in becomes more demanding.

So, to conclude: you would need to come up with an idea where either this trait does not require more energy, and does not hinder procreation, or where the environment allows for a perfect memory to outperform a weaker one in a way that overcompensates the cost. Or more bluntly: if you can't find a convincing answer to the question why that feature would be advantageous, it will hardly evolve naturally.

Of course, if you really want to, it might just be chance: the few members of your species with that trait were sitting in the cave on a specific day when the rest of the tribe was hit by a falling rock, so they suddenly inherited the ecological nieche without their hungry brains having anything to do with the fact that no individual without that trait was left.
But while that will work, it would be a boring story.

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As I see it, the big problem is storage/redundancy. Information storage has energy/brain volume costs, and an organism with photographic memory will remember everything it senses. Problem is, in general most organisms spend most of their times in situations where remembering what's going on in perfect detail simply won't help them survive. (Look! I just ate a mouthful of grass! And another!) Even in emergency situations (Look! There's a lion stalking us!) remembering everything (Look! There is a lion stalking us! There is a green pebble next to a red pebble at my feet! The sun is at 37 degrees from the horizon and there is a cloud shaped like my cousin in the sky!) isn't going to help much either. So the costs associated with continued acquisition and storage of every detail of every moment of your life seem unlikely to be a Good Thing.

Despite what some bloggers and Tweeters seem to think.

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May I propose that the real solution to this question is for external memory storage to evolve. Setting aside for a moment the fact that we are already sort of moving in that direction... (Will what I'm writing at this moment outlive me? Would an attached video of me typing it on my phone also continue indefinitely?)

If an organism stumbled on a way of "depositing" experience, maybe even literally crystallizing it, in such a way that the external recording could persist, it might have advantages to the whole species, especially if the record was compatible between multiple members of the species.

"What, exactly, did the edible mushrooms look like? And what did the the mushrooms that killed Auntie Grool look like? I saw it all seven mushrooming seasons ago, and afterwards recorded it in the usual cave. Go remember it for yourself."

Obviously we've evolved methods of recording memory. The only alien / implausible aspect would be depositing the information outside of the "organic computer", and having compatibility to input the information again.

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Physical skinprints in intelligent cuttlefish

I can think of only one good way to have an organism with photographic memory, and that is to store images as literal photographs. The organism decides to store an image, and a tiny mechanism deposits tiny bits of pigments (or smaller chemicals representing pigments) on a tiny slip of biologically-produced film, and this film is then stored in the body for later "scanning" and recall (presumably each imprint would have a neural connection to the memories associated with that image, enabling them to be easily "sorted"). You might think it would run out of storage space quickly, but even a decent microfilm can store a high-resolution image in an area the size of a grain of sand; a small physical organ near the optic lobe of the brain could plausibly hold many thousands of biological photographs. (It would not, of course, be able to remember everything the organism has ever witnessed - could you imagine the data storage necessary for a several year long MP4 file?)

As for why this would benefit an organism, or how such a system would evolve, that's trickier. Such a system would be limited in use - there are few practical benefits to such a system that are not handled better by a traditional brain.

In order to derive a plausible method, I will start with my favorite go-to species for exotic speculative evolution, the cuttlefish. Cuttlefish are already a species that maintains a direct connection between their eyes and their skin, which they use for incredible feats of camouflage, capable of mimicking even complex patterns.

A hypothetical group of cuttlefish evolves to be more social and intelligent, and since they are already capable of displaying images on their skin it is only natural for them to communicate directly through images of the thing they are talking about, skipping over the unwieldy "a sound represents a thing" system that we humans were forced to blunder through. But displaying an accurate image of exactly what the creature saw is difficult, which means that information regarding potential food or threats will be lost in translation. Passing information to colony members, or teaching children about the world, becomes much easier if you can display perfect images of the things they should be watching out for. And given that the species already has a direct eye-to-skin system, it isn't entirely implausible for it to develop a system that allows it to store "skinprints" internally over time.

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