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I haven't read this particular paper in-depth, but it reminds me of another one I saw that used a similar approach to find if the model encodes its own certainty of answering correctly. https://arxiv.org/abs/2509.10625
It's all very clear when you mentally replace "LLM" with "text completion driven by compressed training data".

E.g.

[Text copletion driven by compressed training data] exhibit[s] a puzzling inconsistency: [it] solves complex problems yet frequently fail[s] on seemingly simpler ones.

Some problems are better represented by a locus of texts in the training data, allowing more plausible talk to be generated. When the problem is not well represented, it does not help that the problem is simple.

If you train it on nothing but Scientology documents, and then ask about the Buddhist perspective on a situation, you will probably get some nonsense about body thetans, even if the situation is simple.

I have a hard time trying to conceptualize lossy text compression, but I've recently started to think about the "reasoning"/output as just a by product of lossy compression, and weights tending towards an average of the information "around" the main topic of prompt. What I've found easier is thinking about it like lossy image compression, generating more output tokens via "reasoning" is like subdividing nearby pixels and filling in the gaps with values that they've seen there before. Taking the analogy a bit too far, you can also think of the vocabulary as the pixel bit depth.

I definitely agree replacing AI or LLMs with "X driven by compressed training data" starts to make a lot more sense, and a useful shortcut.

> Text copletion driven by compressed training data...solves complex problems

Sure it does. Obviously. All we ever needed was some text completion.

Thanks for your valuable insight.

Why shouldn't you expect a problem's simplicity to correlate tremendously with how well it is represented in training data? Every angle I can think of tilts in that direction. Simpler problems are easier to remember and thus repeat, they come up more often, asd they require less space/time/effort to record (which also means they are less likely to contain errors).
This is a popular take on HN yet incomplete in its assessment of LLMs and their capabilities.
oh man i am pretty tired of the “it’s just autocomplete” armchair warriors… it is an accurate metaphor in only the most pedantic of ways, and has zero explanatory power whatsoever as far as intuition building goes. and i don’t even understand the impulse. “reality is easy, it’s just quantum autocomplete!”
> It's all very clear when you mentally replace "LLM" with "text completion driven by compressed training data".

So you replace a more useful term with a less useful one?

Is that due to political reasons?

> It's all very clear when you mentally replace "LLM" with "text completion driven by compressed training data".

This isn't what LLMs are, of course, but what some political groups insist they are so they can strengthen copyright law by pointing to LLMs as "theft". It's all very pro-Disney, of course.

Probably irrelevant, but something funny about claude code is it will routinely say something like "10 week task, very complex", and then one-shot it in 2 minutes. I didn't have it create a feature for a while because it kept telling me it's way too complicated. All of the open source versions I tried weren't working, but I finally just decided to get it to make the feature anyways and it ended up doing better than the open source projects. So there's something off about how well claude estimates the difficulty of things for it, and I'm wondering if that makes it perform worse by not doing things it would do well at.
In terms of the time estimates: I've added to my global rules to never give time estimates for tasks, as they're useless and inaccurate.
I wonder if it's trying to predict what kind of estimate a human engineer would provide.
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I think there's two aspects to this.

Firstly, Claude's self concept is based around humanity's collective self-concept. (Well, the statistical average of all the self-concepts on the internet.)

So it doesn't have a clear understanding of what LLMs' strengths and weaknesses are, and itself by extension. (Neither do we, from what I gathered. At least, not in a way that's well represented in web scrapes ;)

Secondly, as a programmer I have noticed a similar pattern... stuff that people say is easy turns out to be a pain in the ass, and stuff that they say is impossible turns out to be trivial. (They didn't even try, they just repeated what other people told them was hard, who also didn't try it...)

Not sure how related this is, but I've noticed it has a tendency to start sentences with usually inflated optimism and I think the idea is that if it has a tendency to intro with "Aha I see it now! The problem is" whatever comes next has a higher tendency to be a correct solution than if you didn't use an overtly positive prefix, even if that leads to a lot of annoying behavior.
I've always been taught to slightly overestimate how long something will take so that it reflects better on the team when it's delivered ahead of schedule. There's bound to be a bunch of similar advice and patterns in the training data.
Sound a lot like Kolmogorov complexity
My interpretation of the abstract is that humans are pretty good at judging how difficult a problem is and LLMs aren't as reliable, that problem difficulty correlates with activations during inference, and finally that an accurate human judgement of problem difficulty (*as input) leads to better problem solving.

If so, this is a nice training signal for my own neural net, since my view of LLMs is that they are essentially analogy-making machines, and that reasoning is essentially a chain of analogies that ends in a result that aligns somewhat with reality. Or that I'm as crazy as most people seem to think I am.

Umm.. arent the point of analogies is to find similarity between stuff, but reasoning is to find causality between stuff?