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Improving Language Models with MORCELA

MORCELA adjusts language model scores to better reflect human language judgment.

Lindia Tjuatja, Graham Neubig, Tal Linzen, Sophie Hao

― 6 min read


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Have you ever wondered why some sentences sound just right while others make you go, "Huh?" Well, that’s the gist of what we are talking about here. Language Models (LMs), the fancy algorithms that help computers understand and generate text, sometimes struggle to rate sentences the way we humans do. It turns out, the length of a sentence and how often certain words show up can really mess with their scores.

The Challenge of Winning Over Humans

When we compare how well LMs do against our human instincts about language, we notice some quirks. For starters, if a sentence is longer, LMs tend to give it a lower score. Similarly, if it includes words that don’t pop up often in conversations, the scores drop again. Humans, on the other hand, often brush off these factors.

So, in a world where LMs need to align with our Acceptability Judgments, it’s crucial to understand how to tweak their output to match our human sensibilities.

Enter MORCELA

To fix the issues that LMs face when trying to rate sentences, a new theory called MORCELA has entered the chat. Think of it as a recipe that adjusts how we look at the LM scores against our acceptability judgments. It takes into account the length of the sentence and the frequency of specific words, but in a way that’s tailor-made for each sentence.

Instead of applying the same rules across the board, MORCELA learns from real data to figure out the best adjustments needed for each sentence. In our tests, MORCELA has shown to be better at predicting how acceptable a sentence is compared to an older method.

Size Matters

Oh, and here’s the kicker: bigger models (those with more parameters) are usually better at guessing human judgments. It’s like the bigger your dictionary, the better you can weigh in on which words sit well together. However, they still need some tweaking for Word Frequency and sentence length. The good news is that these larger models don’t need as much adjustment as smaller ones.

The Function of Acceptability Judgments

Acceptability judgments are basically what people think about the well-formedness of sentences. We ask folks to rate sentences from "completely unacceptable" to "absolutely fine." These ratings help build theories in linguistics, guiding how we understand language patterns.

When we look at how LMs give scores, we need a way to connect these scores to human judgments. Since it’s a bit of a puzzle, researchers have come up with ways to bridge the gap between what LMs generate and how humans respond.

The Old Way: SLOR

A lot of the previous research used a method called the syntactic log-odds ratio (SLOR) to make sense of LMs scores. The idea was simple: score a sentence based on average probabilities and adjust for length and word frequency.

But here’s the twist: this method didn’t necessarily click with every model or every sentence. The assumptions behind SLOR, like treating length and frequency as equals, don’t work across the board.

Better Predictions with MORCELA

That’s where MORCELA shines. By giving models the flexibility to have different rules for different sentences, we noticed that it correlates better with human judgments. What that means is this new method allows LMs to adapt based on the size and complexity of the model.

We looked at how well each model did when predicting acceptability and found that adding MORCELA’s parameters made a real difference. In some cases, it even improved the correlation dramatically.

Testing the Waters

To test how well these linking functions work, we used various sentences to see how well LMs score them. We measured how much these scores matched up with human ratings. We played around with some models that ranged from small to really, really big.

The results were enlightening. Larger models were much better at predicting what humans thought about sentences. As the size of the model increased, so did the chances that it would guess human judgments correctly.

Adjustments Matter

Interestingly, we also discovered that the adjustments for length and frequency that SLOR set were not quite right. The values it used were based on assumptions that didn’t apply evenly across all models.

Using MORCELA, we found that as models improved, the importance of length and frequency became less pronounced. Larger models didn’t need to adjust as much for infrequent words, which shows they have a better grasp on context.

The Secret to Predicting the Rare

Now, let’s get to why this matters. The better a model is at predicting rare words in context, the less it needs to analyze word frequency. For instance, if a model knows how to handle scientific terms in a research paper, it doesn’t sweat the rarity of those words because context gives them meaning.

The Battle of the Judgments

Think of it like this: if you’re asked to rate sentences, you might find yourself leaning more on how they sound and feel rather than their length or how frequently certain words appear. Humans have a knack for “going with the flow.” So, when LMs can reflect that approach, they tend to do better.

That’s precisely why MORCELA’s approach to tuning parameters is a game-changer. It allows for a better understanding of how LMs can align with human judgments, leading to more natural-sounding outputs.

Turning the Tables on the Assumptions

In our experiments, we found that the SLOR method had some pretty off-the-mark assumptions. It treated length and frequency as if they held the same weight across the board. But that wasn’t true.

MORCELA breaks free from this mold, letting the models learn how much weight to assign to these factors based on what works best in reality.

The Quest for Closer Matches

The ultimate goal is to get LMs to match human judgments more closely. But while MORCELA offers a refined approach, there’s still a noticeable gap between what models predict and what actual human annotators say.

Future research could dive deeper into what else can drive models closer to human-like understanding. The quest continues!

Limitations and Future Directions

Of course, there are some limits to this study. Our evaluations focused on English models with data from English sentences. We can’t say how well these findings translate to other languages or settings yet.

But the insights we gained can help shape future models, making them more intuitive and aligned with how people really use language.

In Closing

So, what’s the takeaway? Language models have come a long way, but they still have work to do in understanding how we judge acceptability. By refining their methods with techniques like MORCELA, we can help them bridge the gap between numbers and nuance.

Thinking of sentences as more than just strings of text but rather as part of a larger communicative dance can help us build smarter models that get closer to the way humans think and talk.

Original Source

Title: What Goes Into a LM Acceptability Judgment? Rethinking the Impact of Frequency and Length

Abstract: When comparing the linguistic capabilities of language models (LMs) with humans using LM probabilities, factors such as the length of the sequence and the unigram frequency of lexical items have a significant effect on LM probabilities in ways that humans are largely robust to. Prior works in comparing LM and human acceptability judgments treat these effects uniformly across models, making a strong assumption that models require the same degree of adjustment to control for length and unigram frequency effects. We propose MORCELA, a new linking theory between LM scores and acceptability judgments where the optimal level of adjustment for these effects is estimated from data via learned parameters for length and unigram frequency. We first show that MORCELA outperforms a commonly used linking theory for acceptability--SLOR (Pauls and Klein, 2012; Lau et al. 2017)--across two families of transformer LMs (Pythia and OPT). Furthermore, we demonstrate that the assumed degrees of adjustment in SLOR for length and unigram frequency overcorrect for these confounds, and that larger models require a lower relative degree of adjustment for unigram frequency, though a significant amount of adjustment is still necessary for all models. Finally, our subsequent analysis shows that larger LMs' lower susceptibility to frequency effects can be explained by an ability to better predict rarer words in context.

Authors: Lindia Tjuatja, Graham Neubig, Tal Linzen, Sophie Hao

Last Update: Nov 4, 2024

Language: English

Source URL: https://arxiv.org/abs/2411.02528

Source PDF: https://arxiv.org/pdf/2411.02528

Licence: https://creativecommons.org/licenses/by-nc-sa/4.0/

Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.

Thank you to arxiv for use of its open access interoperability.

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