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From tokens to thoughts: How LLMs and humans trade compression for meaning (arxiv.org)
124 points by ggirelli on Jun 5, 2025 | hide | past | pdf | 25 comments on HN

In plain words: They measured how much information AI models keep when sorting concepts, comparing it with how humans group classic categories. Models matched broad human groupings but squeezed out fine detail, and smaller understanding-focused models fit human thinking better than much larger text generators.

Abstract · From Tokens to Thoughts: How LLMs and Humans Trade Compression for Meaning

Humans organize knowledge into compact conceptual categories that balance compression with semantic richness. Large Language Models (LLMs) exhibit impressive linguistic abilities, but whether they navigate this same compression-meaning trade-off remains unclear. We apply an Information Bottleneck framework to compare human conceptual structure with embeddings from 40+ LLMs using classic categorization benchmarks. We find that LLMs broadly align with human category boundaries, yet fall short on fine-grained semantic distinctions. Unlike humans, who maintain ``inefficient'' representations that preserve contextual nuance, LLMs aggressively compress, achieving more optimal information-theoretic compression at the cost of semantic richness. Surprisingly, encoder models outperform much larger decoder models in human alignment, suggesting that understanding and generation rely on distinct representational mechanisms. Training-dynamics analysis reveals a two-phase trajectory: rapid initial concept formation followed by architectural reorganization, during which semantic processing migrates from deep to mid-network layers as the model discovers increasingly efficient, sparser encodings. These divergent strategies, where LLMs optimize for compression and humans for adaptive utility, reveal fundamental differences between artificial and natural intelligence. This highlights the need for models that preserve the conceptual ``inefficiencies'' essential for human-like understanding.

Chen Shani, Liron Soffer, Dan Jurafsky, Yann LeCun, Ravid Shwartz-Ziv
arXiv:2505.17117 · cs.CL, cs.AI, cs.IT · submitted May 21, 2025 · updated Aug 19, 2026
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Also discussed: May 2025 (2 points, 0 comments)

>> For each LLM, we extract static, token-level embeddings from its input embedding layer (the ‘E‘matrix). This choice aligns our analysis with the context-free nature of stimuli typical in human categorization experiments, ensuring a comparable representational basis.

They're analyzing input embedding models, not LLMs. I'm not sure how the authors justify making claims about the inner workings of LLMs when they haven't actually computed a forward pass. The EMatrix is not an LLM, its a lookup table.

Just to highlight the ridiculousness of this research, no attention was computed! Not a single dot product between keys and queries. All of their conclusions are drawn from the output of an embedding lookup table.

The figure showing their alignment score correlated with model size is particularly egregious. Model size is meaningless when you never activate any model parameters. If Bert is outperforming Qwen and Gemma something is wrong with your methodology.

Note that the token embeddings are also trained, therefore their values do give some hints on how a model is organizing information.

They used token embeddings directly and not intermediate representations because the latter depend on the specific sentence that the model is processing. Data on human judgment was however collected without any context surrounding each word, thus using the token embeddings seem to be the most fair comparison.

Otherwise, what sentence(s) would you have used to compute the intermediate representations? And how would you make sure that the results aren't biased by these sentences?

You can process a single word through a transformer and get the corresponding intermediate representations.

Though it sounds odd there is no problem with it and it would indeed return the model's representation of that single word as seen by the model without any additional context.

Embedding models are not always trained with the rest of the model. That’s the whole idea behind VLLMs. First layer embeddings are so interchangeable you can literally feed in the output of other models using linear projection layers.

And like the other commenter said, you can absolutely feed single tokens through the model. Your point doesn’t make any sense though regardless. How about priming the model with “You’re a helpful assistant” just like everyone else does.

It’s mind blowing LeCun is listed as one of the authors.

I would expect model size to correlate with alignment score because usually model sizes correlate with hidden dimension. But also opposite can be true - bigger models might shift more basic token classification logic into layers and hence embedding alignment can go down. Regardless feels like pretty useless research…

Leaves a bit of a taste considering LeCun's famously critical stance on auto-regressive transformer LLMs.
the llm is also a lookup table! but your point is correct. they should have looked at subsequent layers that aggregate information over distance.
This paper is interesting, but ultimately it's just restating that LLMs are statistical tools and not cognitive systems. The information-theoretic framing doesn’t really change that.
> LLMs are statistical tools and not cognitive systems

I have never understood broad statements that models are just (or mostly) statistical tools.

Certainly statistics apply, minimizing mismatches results in mean (or similar measure) target predictions.

But the architecture of a model is the difference between compressed statistics vs. forcing a model to translate information in a highly organized way reflecting the actual shape of the problem to get any accuracy at all.

In both cases, statistics are relevant, but in the latter it's not a particularly insightful way to talk about what a model has learned.

Statistical accuracy, prediction, etc. are basic problems to solve. The training criteria being optimized. But they don't limit the nature of solutions. They both leave problem difficulty, and solution sophistication unbounded.

my take from the paper is that the authors overstate the following:

LLMs cannot zoom in and out of certain details, while we humans subconsciously zoom in and out of context and even go through conceptual spaces in the very hermetic sense of it. LLMs do not. they work on the present context, which kickstarts them into expounding likeliness in the same contextual space.

Am I the only one that is lost on how the calculations are made?

From what I can tell this is limited in scope to categorizing nouns (robin is a bird).

Open a bank account. Open your heart. Open a can. Open to new experiences.

Words are a tricky thing to handle.

And that is just in English

Other languages have similar but fundamentally different oddities which do not translate cleanly

Not sure how they're fundamentally different. What do you mean?
Think about the work of localizing a joke that relies on wordplay or similar sounding words to be funny. Or simply how words rhyme

Try explaining why tough and rough rhyme but bough doesn't

You know? Language has a ton of idiosyncrasies.

ChatGPT is horrible at producing Dutch rhymes (for Sinterklaas poems) until you realize that the words it comes up with do rhyme when translated to English.
To make it more concrete - here's an example in Chinese: https://en.wikipedia.org/wiki/Grass_Mud_Horse
> 2009, renowned artist Ai Weiwei published an image of himself nude with only a 'Caonima' hiding his genitals, with a caption "草泥马挡中央" (cǎonímǎ dǎng zhōngyāng; 'a Grass Mud Horse covering the center'. One interpretation of the caption is: "fuck your mother, Communist Party Central Committee"). Political observers speculated that the photo may have contributed to Ai's arrest in 2011 by angering Chinese Communist Party hardliners.

How did I never hear about this detail??

Right but I wouldn't call those things fundamentally different. That's just having different words; the categories of idiosyncrasies are still the same.
As most languages allow expressions of algorithms, they are all Turing complete and, thus, are not fundamentally different. The complexity of expressions of some concepts is different, though.

My favorite thing is a "square." I put that name to an enumeration that allows me to compare and contrast things with two different qualities expressed by two extremes.

One such square is "One can (not) do (not do) something." Both "not"'s can be present and absent, just like a truth table.

"One can do something", "one can not do something", "one can do not do something" and, finally, "one can not help but do something."

Why should we use "help but" instead of "do not"?

While this does not preclude one from enumerating possibilities thinking in English, it makes that enumeration harder than it can be in other languages. For example, in Russian the "square" is expressible directly.

Also, "help but" is not shorter than "do not," it is longer. Useful idioms usually expressed in shorter forms, thus, apparently, "one can not help but do something" is considered by Englishmen as not useful.

I agree in general, but I think that "open" is actually a pretty straightforward word.

As I see it, "Open your heart", "Open a can" and "Open to new experiences" have very similar meanings for "Open", being essentially "make a container available for external I/O", similar to the definition of an "open system" in thermodynamics. "Open a bank account" is a bit different, as it creates an entity that didn't exist before, but even then the focus is on having something that allows for external I/O - in this case deposits and withdrawals.

And models since BERT and ELMo capture polysemy!

https://aclanthology.org/2020.blackboxnlp-1.15/

OpenAI agrees
incomplete inaccurate off misleading meandering not quite generation prediction removal of superfluous fast but spiky

this isn’t talking about that.

Stochastic parrots