In your post, Russ, you say: 

“They are trained to produce fluent language, not to produce valid statements.“ 

Is that actually, operationally, what they are trained to do?  I speak from a 
position of ignorance here, but my impression is that they are trained to 
effectively stitch together fragments of varying lengths, according to rules 
for what stitchings are “compatible”.

My thinking here is metaphorical, to homologous recombination in DNA.  Some 
regions that don’t start out contiguous can be concatenated by DNA repair 
machinery, because under the physics to which it responds, they have plausible 
enough overlap that it considers them “compatible” or eligible to be identified 
at the join region, their “mis-matches” edited out.  Other pairs are so 
dissimilar that, under its operating physics, the repair machinery will 
effectively never join them.

My metaphor isn’t great, in the sense that if what LLMs (for human speech) are 
doing is “next-word prediction”, that says that the notion of “joining” is 
reduced formally to appending next-words onto strings.  Though, to the extent 
that certain substrings of next-words are extremely frequently attested across 
the corpus of all the training expressions, one would expect to see extended 
sequences essentially reproduced as fragments with large probability.

If my previous two characterizations aren’t fundamentally wrong, it would 
follow that fluent speech-generation becomes possible because the 
compatible-joining relations are suffficiently strong in human languages that 
the attention structures or other feed-forward aspects of the architecture have 
no trouble capturing them in parameters, even though human linguists trying to 
write them as re-write rules from which a computer could generate native-like 
speech failed for decades to get anywhere close to that.  My interpretation 
here would be consistent with what I believed was the main watershed change in 
the LLMs: that the parametric models would, ultimately, have terribly few 
parameters, whereas the LLMs can flood-fill a corpus with parameters, and then 
try to drip out the parts that don’t “stick to” some pattern in the data, and 
are regarded as the excess entropy from the sampling algorithm that the 
training is supposed to recognize and remove.  It is easy to imagine that 
fluent speech has far more regularities than rule-book linguists captured 
parametrically, but still few enough that LLMs can have no trouble attaching to 
almost-all of them, with parameters to spare.  Hence fluent speech could be 
epiphenomenal on what they are (operationally, mechanistically) being trained 
to do, but a natural summary statistic for the effectiveness of that training, 
and of course the one that drives market engagement.

But if the above is the case, then the question of when they get “the syntax” 
right and “the semantics” wrong, would seem to turn on how much context from 
the training set is needed to identify semantically as well as syntactically 
appropriate “allowed joins” of fragments.  When short fragments contain enough 
of their own context to constrain most of the semantics, the stitching training 
algorithm has no reason to perform any worse at revealing the semantic signal 
in the training set than the syntactic one.  But if probability needs to be 
withheld for a long time in the prediction model, driving it to prioritize a 
much smaller number of longer or more remote assembled inputs from the training 
data, it could still do fine on syntax but fail to “find” and “render” the 
semantic signal in the training data, even if that signal is present in 
principal.  

I would not feel a need to use terms like “understanding” anywhere in the 
above, to make predictions of what kinds of successes or failures an LLM might 
deliver from the user’s perspective.  It seems to me like something that all 
lives in the domain of hardness-of-search combinatorics in data-spaces with a 
lot of difficult structure.

Eric


> On Sep 10, 2025, at 7:02, Russ Abbott <[email protected]> wrote:
> 
> 
> OpenAI just published a paper on hallucinations 
> <https://linkprotect.cudasvc.com/url?a=https%3a%2f%2fcdn.openai.com%2fpdf%2fd04913be-3f6f-4d2b-b283-ff432ef4aaa5%2fwhy-language-models-hallucinate.pdf&c=E,1,IvBfvLzhn3L6LCNk3_ktKoEbc9NI2Oqq8vlFpNcIXCHElptIB-Fx-UxQYyTnCFW_ToeD5Kd4RjHkY-6fLxSBqZueOcvRqyHwpsHPK9ugMNcsOw,,&typo=1>
>  as well as a post summarizing the paper 
> <https://linkprotect.cudasvc.com/url?a=https%3a%2f%2fopenai.com%2findex%2fwhy-language-models-hallucinate%2f&c=E,1,tEcctM28Lbt5XBi3gNiUX-RiFelMYHNq6K3VJBilGv1_Z8uAt34ta8FaU-FcW5i8V3-2tsjNPu_at8Es78G2_drdmykgOltvjRvvaw1hUgnXUsv3&typo=1>.
>  The two of them seem wrong-headed in such a simple and obvious way that I'm 
> surprised the issue they discuss is still alive. 
> 
> The paper and post point out that LLMs are trained to generate fluent 
> language--which they do extraordinarily well. The paper and post also point 
> out that LLMs are not trained to distinguish valid from invalid statements. 
> Given those facts about LLMs, it's not clear why one should expect LLMs to be 
> able to distinguish true statements from false statements--and hence why one 
> should expect to be able to prevent LLMs from hallucinating. 
> 
> In other words, LLMs are built to generate text; they are not built to 
> understand the texts they generate and certainly not to be able to determine 
> whether the texts they generate make factually correct or incorrect 
> statements.
> 
> Please see my post 
> <https://linkprotect.cudasvc.com/url?a=https%3a%2f%2frussabbott.substack.com%2fp%2fwhy-language-models-hallucinate-according&c=E,1,zLy4H6KEpD5hDchYiBUjiH2J5dG2O9bmqa-jm1z6mGgRSqZgDKaVd2D2Xh_2Wuzi7FtZu2kjIOTNjQuk4iwsnfNUG68UPCxmZvD_IHTVUEPTcW6HDgpmcozzRQ,,&typo=1>
>  elaborating on this.
> 
> Why is this not obvious, and why is OpenAI still talking about it?
> 
> -- Russ Abbott 
> <https://linkprotect.cudasvc.com/url?a=https%3a%2f%2frussabbott.substack.com%2f&c=E,1,cKMmq0etz4RiUaE4G2F04re6Su0EnNyqR9j5Dx8RcccQVNOB2r5CMNBzxRL9EYmN3lG_11nhB4wP-5jPf7NR86Mb9VxP9Jn2YUdKPZQT&typo=1>
>   (Click for my Substack)
> Professor Emeritus, Computer Science
> California State University, Los Angeles
> 
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