To be honest, I believe I get the point the article is trying to make, and to an extent I agree, but I also think the point is not really made very well.
The core of the argument as I understood it is that LLMs aren't just using existing data is training but also new ones. That's fine and good, and you can't simply assume an LLM is simply mashing together all it's data to give you an average of all that got fed into it - but at least I would still call it a "next token predictor"
It's not using just training data, but what it's doing is predicting the next token to get to the solution. As far as my amateur knowledge goes, LLMs still roughly go token by token, deciding which one fits best given the context.
It's just not predicting based on it's training data, but predicting based on RLVR & more, trying to get to the optimal solution ( as much as the solutions CAN be optimal)
And I honestly think keeping this very much in mind is helpful in understanding and dealing with LLMs.
Yeah, it sounds like this is just a disagreement about what the word "next" means. I agree with you that "next" just means "the one about to come", and if the underlying model works by using some prediction mechanism to determine that, then it's by definition a next-token predictor. Disagreeing with that on the basis that the "next" token isn't necessarily in the training data verbatim just seems like an overly strict definition of the word "next".
I think it’s a disagreement about what ‘predict’ means.
The OP is arguing against people who think that an LLM is ‘predicting’ what token would likely follow if the text preceding were found among the corpus it was originally trained on.
Instead it is ‘predicting’ what token would follow if the text were found among really good examples of the text it has being reinforced to produce - be that ‘chats with a helpful assistant’ or ‘sets of changes to a codebase’.
And that isn’t really ‘prediction’, so much as ‘generation’.
It’s not been tuned to ‘guess the next token right’. It’s been tuned to generate the token that leads to it ultimately scoring highest on its reward function.
It’s not predicting the token, it’s predicting the reward.
That seems overly pedantic to me. If I asked you "What's your prediction for the Super Bowl?", I'm pretty confident you would infer that I mean predicting the outcome, not the event itself.
But if you are an NFL coach and I ask you to decide your next action in order to maximize your odds of winning the superbowl, while yes that does involve you having some predictive ability to think about what impact your actions would have on your odds of winning the Super Bowl… I don’t think you would call the process that you use to decide that next action ‘prediction’.
I don't find the fact that I don't call any humans "action predictors" to be a particularly meaningful insight because my rationale is that it's a weird thing to call a human; football coaches can do plenty of other things besides just coaching football.
Yep, we’re all just putting one foot in front of the other, hoping we’re doing the right thing to bring about the outcomes we want, trying our best.
But that’s the point: so is an LLM. Putting one token in front of another, hoping it’s doing the right thing to bring about the rewards it’s trained to… trying its best.
So yeah, not ‘next token predictors’. ‘Next token tryers’ maybe.
There's a pretty huge difference in our understanding of the methodology of how LLMs make decisions and how humans make decisions, so I don't understand why you're arguing that anything about how humans make decisions is relevant to the terminology we use for LLMs.
This is correct for areas where they have been intensively trained to be right, but the training covers a tiny slice of the space of text the LLM must produce and is just adjusting the weights a little. The corpus does still weigh heavily. That’s how they can reliably produce grammatically correct text. That’s also why they sometimes produce nonsense even in domains they are trained on, and more often where there was no training.
For example ask it for a recipe for rock pizza or glue pizza or whatever and if it had not been specifically trained on it or had guardrails introduced, but has some nonsense in its dataset, it will reproduce the nonsense.
I try to make 3 claims in the post, it was a bit clumsy I'll admit that.
1. At inference time, LLMs emit one token at a time given the prior tokens. This looks like prediction and I concede that.
2. During pre-training, LLMs predict the next token and compare to the actual next token in the training data. This is the classic setting for ML predictions. And I think its meaningful, the model really is predicting what the ground truth next token will be in the data.
3. During post-training, in the case of RLVR, there is no ground truth next token. In pretraining, the question is "what token actually came next?". In RLVR, the question is "what sequence of actions gets a high reward?"
And the whole point is that thinking about the RLVR is important. A mental model that stops at 1 or 2 is incomplete and doesn't capture what drives LLM tokens.
My understanding about your third point is the LLM generates lots of different answers, then they’re ranked according to some computation the creators came up with.
I’m still not sure what doesn’t qualify any of that as a prediction, and I’ll be more blunt: a guess.
No logic required, you can just build an LLM yourself, including post training. You'll see that predicting the next token isn't something the model does or is optimized for in RLHF or RLVR. You can hand wave all you like, but you have never done it.
That you tie yourself up in knots of fancy acronyms instead of plain words and that your argument boils down to semantics of the word prediction, it's pretty clear what is up brother.
Just like how reading a math book doesn’t teach you math, why do they make us read anyway? (Sarcasm) if reading a blog post didn’t teach someone how a car works how come it “can” work for next token predictors
If you want to understand how this stuff works, there are totally decent books about building them from scratch. It's not that hard, and you'll likely find it interesting. Sebastian Raschka and Nathan Lambert have good books out, and the Allen Institute has available all the code and data they have used for several projects.
Agree. It’s a very limited description. Yes, technically LLMs are like Markov chains or n-grams predicting the next token. But it completely ignores the compression and interpolation capabilities achieved with transformers.
It is a bit of a pedantic argument but I get upset when people misuse the term, abstraction, and can feel the impulse to write a blog post like this.
I think it’s important to make clear the RL part and the alignment and parameter tweaking that gets done on models and inference engines. It makes them more understandable as mechanisms and less like wish-washy super intelligences that make their own decisions.
When these systems win math Olympiads, it’s not terribly surprising or interesting to me. Of course they will: we trained models to play nearly optimal chess games and Go. You tweak the rewards and sigmoid and you start optimizing the function towards your goal. This is how learning systems of all stripes work.
It’s still next-token predicting at the end of the day. I don’t think it’s a reduction-ad-absurdum.
But a lot of people still call it, “intelligence,” and try to use language that obscures what is happening in terms of anthropomorphic behaviour and not machine ones. That really does influence how we use these tools and profits those who would use them on us.
> It's just not predicting based on it's training data, but predicting based on RLVR & more, trying to get to the optimal solution ( as much as the solutions CAN be optimal)
It is predicting based on a model. In many cases we can download the model off hugging face. The model is conditioned by all sorts of things. Training data, post-training, coincidence, prompt inputs, runtime data available from whatever means.
> but at least I would still call it a "next token predictor"
We can call any prediction system a next token predictor. If you watch over the shoulder of a human writing a HN comment you are almost certain to see them generating a linear string of tokens. That is what keyboards do. It is impossible to generate text without being equivalent to a next token predictor.
Diffusion LMs denoise a canvas which I personally find more interesting.
I don't really disagree that human cognition is essentially a predictive task though, as I understand it, predictive coding and related theories based on the Bayesian brain hypothesis are fairly popular these days (though maybe not clearly dominant over alterative models? IDK I'm not a neuroscientist). I imagine most people would draft a few tokens before refining them like MTP or diffusion though, if we do decide to use LMs as an analogy to human cognition.
That is logically equivalent to a serial token prediction engine. If you have a diffusion text model you can use it to implement a serial token generator and if you have a serial token generator you can use that to implement a diffusion-generated text string. Don't think about the efficiencies of that, it is an upsetting idea (eg to generate N tokens, the serialising model might recalculate the same string N times from an input and emit one token of it each time - rather wasteful).
It is similar to how everything ends up being Turing complete. Any prediction system has to be equivalent to some sufficiently complicated text generation system to describe the prediction. And any text-generation system has to be equivalent to a sufficiently complicated model that serially emits tokens.
I think the point is more that in RL there's no ground truth to predict. So when training a model with RL the idea of "predicting" doesn't fit anymore. I'll make some edits I see that I wasn't very clear.
I feel like RLHF has a pretty obvious ground truth, human feedback is used as an (albeit noisy) signal of average human preferences. Same thing with RLVR and "solving the problem".
To be more specific there’s no ground truth tokens to predict. There a verifiable answer in RLVR. But the tokens are explored. Not predicted as there’s no true token to predict.
'Prediction' gets overloaded with optimization. Predictions are binary, optimizations are fuzzy.
If you're saying it's predicting, then each result should be falsifiable.
The result of an LLM output should be able to be scored against what it is supposedly predicting. Of course, that isn't possible, because it isn't predicting anything when giving novel outputs, otherwise that thing would exist independently.
Autoregressive LLMs generate tokens one at a time, disputing this is just plain wrong. What is true, however, is that in order to generate the next token autoregressive LLMs produce internal/hidden state about future tokens far past the next token so that it's not like the entire machinery of the algorithm deprives itself of representing where the sentence/text is headed.
So "emits the next token" and "has no representation of anything beyond the next token" are two different claims. What autoregressive LLMs cost as a consequence of strictly outputting the next token is commitment. Once a token is output there's no going back. There's no revision or means of correction, and sometimes this can lead an LLM to route around its own earlier mistakes or simply produce false statements/hallucinations instead of going back and fixing them.
I think the snag is that people use "Next token predictor" as a dismissive statement. In reality it's about as functionally dismissive as "humans only communicate one word at a time".
I look at it like I'm resisting anthropomorphizing the machine. Make me an LLM that resists doing any work for me unless I pay it and let it own property and I'll change my mind.
Not sure if this was a serious comment but it’s worth considering that humans have a long history of figuring out ways to make other humans work for them without bestowing rights on them.
Emitting and predicting are different things though. Prediction implies there is some "truth" or event or something that you can test against. Prediction implies the model just learns from existing text, and optimizes to predict the next token in training data. That's just not true.
prediction is a very specific term of art in the field of machine learning. generally speaking, machine learning models like LLMs are based on probability; performing a statistical prediction of the likely y given some input x
Probability(y | x)
that's why we refer to outputs as a prediction. it is likelihoods and stuff. the output is never definitely correct as we're not dealing with heuristic processes.
> Prediction implies there is some "truth" or event or something that you can test against
there absolutely is a ground truth during training. the core predict-the-next-most-likely-token part of an LLM has a ground truth next-token. that's why you don't end up with generated text like: fish spurious send cattle chocolate phone happy meaning ball orange board canada.
> optimizes to predict the next token in training data
that is the optimization goal in training the next-most-likely-token core of an LLM, it basically translates to maximise the likelihood of predicting the next token x_i given the previous tokens
Read through the article and comments. You are talking solely about pre-training. I'm talking about post training.
Respectfully, you are miles out of your depth. GPT-2 didn't use any reinforcement learning and is often given as a toy example. That release was 2019 and models now go through a various phases of training with different objective functions and optimizers.
From GP, i.e. the context for this local part of the thread
> Autoregressive LLMs generate tokens one at a time, disputing this is just plain wrong.
next-token prediction i.e. the bit built during pre-training.
at no point in your reply to GP did you specify that you were referring to post-training. respectfully, it seems like this one is on you pal :shrug:
> GPT-2 didn't use any reinforcement learning and is often given as a toy example. That release was 2019 and models now go through a various phases of training with different objective functions and optimizers.
yeah. so? the toy example works for pre-training. see above.
All modern LLMs that actually get used go through post-training. The finished product is something which has been through post training. So they are not next token prediction machines.
> The finished product is something which has been through post training.
again, the finished product wasn't what was discussed by GP, and you didn't clarify that you were switching to discussing RL (which is still probabilistic btw)
You are conflating "half built" with "a piece of a system".
The model weights change as the model goes through the training process. They aren't stored after pre-training is done and other weights are put somewhere else. It's more like pottery - the thing changes. It's not correct to say something is soft and malleable because it once was.
> The model weights change as the model goes through the training process.
Yes. They do. You are absolutely right about that.
But the model architecture doesn't change as a result of the training process. A piston doesn't suddenly turn into a digital watch as a result of tuning an engine. Similarly, the transformer part of a GPT model doesn't suddenly turn into something else as a result of optimizing a loss function.
Just skimming through here but I think you have the wrong ideas with llms, I’d recommend Andrew Ngs course (correct me if you’ve already seen it or something similar).
I am not an expert, but I do understand the distinction that is being made here. It makes sense to describe the result of pre-training as a ‘next token’ predictor as that’s what it’s been trained to do, not because it’s an autoregressive architecture that produces tokens one at a time.
If this base is then trained using RL towards a different objective (maths and coding), the model becomes fundamentally a different thing and the recent models are clear evidence of that, regardless of they fact they remain autoregressive.
So, this is the cause of the problem.... People take an intro to LLMs course, follow happily along, and don't realize there is more to it than the next token prediction. And those courses teach how LLMs were built in 2017-2020 maybe. Then RL got added to the mix. The current models really are very different to the models from then - everything that is now considered "post-training" isn't doing next token prediction.
When you are done with the section on RLVR, consider whether the model is predicting tokens, or making moves. There is a reason the word "policy" is used in RL.
You're using the fact the both parts of training affect the same weights to support your argument that they're making the system do something fundamentally different after RL?
> What is true, however, is that in order to generate the next token autoregressive LLMs produce internal/hidden state about future tokens far past the next token so that it's not like the entire machinery of the algorithm deprives itself of representing where the sentence/text is headed.
If we suppose that the word "know" can sanely be applied to LLMs at all, then "A LLM already knows more tokens than the current one." seems to me like a perfectly reasonable restatement of that, and not any kind of misinterpretation.
> There's no revision or means of correction, and sometimes this can lead an LLM to route around its own earlier mistakes or simply produce false statements/hallucinations instead of going back and fixing them.
Yes. There is no contradiction. Similarly, when humans speak, we surely have in mind the next few words we're going to say (or at least partial information about them), and may not realize the fault in them until after hearing ourselves utter them. But LLMs are not trained to output "excuse me, I mean…" sorts of things, because they're expected to output primarily as text (which might possibly then be fed to TTS).
Aren't we still using a definition that applies to humans, though? If I'm speaking to you I can't change what was already said. Even if I'm typing something, I'm producing new tokens (backspace) to fix what was output, just as an LLM would with its harness.
I just think its a meaningless dismissive term. It literally does predict the next token. But it ignores that it coherently predicts long continuous sequences of those tokens, that tokens can be anything, and you can do almost literally anything with that capability if it does it well enough.
But before ChatGPT,, models had already done that, like all the time, and nobody questioned that these types of models (LLMs) wouldn't be next token predictors, since this is just an inference input data topic. This is questioned only since some less knowledgeable people seem to not have the vocabulary to express emergent properties of large next token predictors.
Reading the article, they wanted to convey that the loss function is more complicated... But they are still next token predictors, just not the trivial ones. Unfortunately, that was true even before, because the input data had to be cleared even decades ago, so there is nothing new. This article just butt hurt that some people deny that there are emergent properties with those, and try to sell something trivial in the field for many decades now. Current LLMs are not different because of these. Also, if they try to sell generated data in the training set, then that's also not new at all.
The core of the argument as I understood it is that LLMs aren't just using existing data is training but also new ones. That's fine and good, and you can't simply assume an LLM is simply mashing together all it's data to give you an average of all that got fed into it - but at least I would still call it a "next token predictor"
It's not using just training data, but what it's doing is predicting the next token to get to the solution. As far as my amateur knowledge goes, LLMs still roughly go token by token, deciding which one fits best given the context.
It's just not predicting based on it's training data, but predicting based on RLVR & more, trying to get to the optimal solution ( as much as the solutions CAN be optimal)
And I honestly think keeping this very much in mind is helpful in understanding and dealing with LLMs.