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Comment by nemo1618 | Hacker News Reader

To be honest, I have no idea how many distinct objects humans can distinguish between, but I am 99% confident that it is fewer than 2^128, much less 2^256.

I suppose it's a somewhat nuanced question, though. For example, if I were shown every avatar in sequence, I'm quite sure I would always notice the "diff" between two consecutive avatars. But the bar that I have in mind is much, much higher: given a sequence of avatars, can I recognize my friend's avatar with 100% accuracy? Given that we can't even do this within the set of <8 billion human faces (we occasionally accost a stranger as though they were a friend), I have to conclude that doing so within a set of 2^256 abstract shapes is entirely hopeless.

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It is definitely a nuanced question. The definition of object is surely up for debate as well. A silly example: if one were to define an object as a string of 64 hex characters, even non-literate people could distinguish between any two distinct objects.

echo "hello" | sha256sum

>> 5891b5b522d5df086d0ff0b110fbd9d21bb4fc7163af34d08286a2e846f6be03

echo "world" | sha256sum

>> e258d248fda94c63753607f7c4494ee0fcbe92f1a76bfdac795c9d84101eb317

But were I to briefly glance at a computer screen, I'd probably confuse these next two:

e258d248fda94c63753607f7c4494ee0fcbe92f1a76bfdac795c9d84101eb317

e258d248fda94c63753607f7c4494ee0fcbe92f1a76bfaac795c9d84101eb317

FOLLOW-UP: It occurs to me that, actually, plenty of humans could definitely clear my "higher bar." All you need to do is memorize a 64-character hex string, which is difficult but completely doable using a memory palace or similar technique.

Practically speaking, though, this isn't something that the average person is capable of doing. Even memorizing one hex string, let alone multiple (for each of your friends), requires a lot of effort for little benefit.

Furthermore -- if you can memorize the hex directly, you don't need the avatars in the first place! :P

People memorize digits of pi. An outlier for sure, but a 7 year old memorized over 1k digits a few years ago. Pretty crazy!

Yeah, I should've been more clear. There's no doubt that humans can't distinguish/memorize 2^256 abstract shapes. However, only a small subset of those would have to be memorized - those which are relevant to the individual. I'd agree that this particular pattern doesn't have enough variability for each pattern to be unique enough to reliably identify it, but I'd conjecture that its possible to make such a pattern, which has enough variability and unique characteristics to be recognizable (ignoring the fact that an adversary could make a very similar pattern to mislead the individual - I'm not curious about it for verification.)

Your example of the fact that we can't reliably recognize every face on this planet is very interesting. Let's imagine we know n faces which I can reliably distinguish from one another, but now there is a (n+1)th face which I mix up with one of the previous ones. Now lets assume this face would instead have a very unique characteristic, unlike all previous faces - lets imagine for example, the nose on this face is upside down. Surely I'd be able to differentiate it from the previous n faces, hence the issue of identifying it might've been the limited variability/characteristics in the various previous instantiations of a face.

So there are a number of characteristics in a face, which have a certain degree of variability, which enable us to distinguish from a number of them. I've been pondering on how many of those characteristics could be combined in an object, and how high the variability could be; to create uniquely identifiable patterns. It probably depends a lot on the meaning we attribute to the pattern, different associations we have to it.

I apologize - quite the tangent, I guess. I've just been pondering a lot on this for a project I've been working on for some time.

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