China

Multilingual Large Language Models (LLMs) develop cross-lingual abilities despite being trained on limited parallel data. However, they often struggle to generate responses in the intended language, favoring high-resource languages such as English. In this work, we introduce CoCo-CoLa (Correct Concept - Correct Language), a novel metric to evaluate language adherence in multilingual LLMs. Using fine-tuning experiments on a closed-book QA task across seven languages, we analyze how training in one language affects others&#39; performance. Our findings reveal that multilingual models share task knowledge across languages but exhibit biases in the selection of output language. We identify language-specific layers, showing that final layers play a crucial role in determining output language. Accordingly, we propose a partial training strategy that selectively fine-tunes key layers, improving language adherence while reducing computational cost. Our method achieves comparable or superior performance to full fine-tuning, particularly for low-resource languages, offering a more efficient multilingual adaptation.

EMNLP 2025

CoCo-CoLa: Evaluating and Improving Language Adherence in Multilingual LLMs

Multilingual Large Language Models (LLMs) develop cross-lingual abilities despite being trained on limited parallel data. However, they often struggle to generate responses in the intended language, favoring high-resource languages such as English. In this work, we introduce CoCo-CoLa (Correct Concept - Correct Language), a novel metric to evaluate language adherence in multilingual LLMs. Using fine-tuning experiments on a closed-book QA task across seven languages, we analyze how training in one language affects others' performance. Our findings reveal that multilingual models share task knowledge across languages but exhibit biases in the selection of output language. We identify language-specific layers, showing that final layers play a crucial role in determining output language. Accordingly, we propose a partial training strategy that selectively fine-tunes key layers, improving language adherence while reducing computational cost. Our method achieves comparable or superior performance to full fine-tuning, particularly for low-resource languages, offering a more efficient multilingual adaptation.

workshop paper

## Welcome!
"I am excited to welcome you to this year’s edition of the Conference on Empirical Methods in Natural Language Processing! Importantly, it marks the 30th edition of EMNLP. With over 8,000 submissions, more than 3,000 accepted papers, and thousands of attendees, we have come a long way from that first
workshop, which had 14 accepted papers. As the field looks ahead, Suzhou is the fitting location for celebrating this milestone: rooted in a long literary tradition, yet modern and forward-looking, and home to a large share of the NLP community."<br>

*Message from the General Chair, Dirk Hovy*

[**Link to Conference Handbook**](https://drive.google.com/file/d/1johU5QqVVYO4RfH7QcIORr7qrVBdzdwC/view?usp=sharing)





<br>

Celebrate 30 Years of EMNLP! 
EMNLP 2025 will be held in Suzhou, China from November 5th to November 9th, 2025.

We present an uncertainty‐based approach to Partial Diacritization (PD) for Arabic text. We evaluate three uncertainty metrics for this task: Softmax Response, BALD via MC-dropout, and Mahalanobis Distance. We further introduce a lightweight Confident Error Regularizer to improve model calibration. Our preliminary exploration illustrates possible ways to use uncertainty estimation for selectively retaining or discarding diacritics in Arabic text with an analysis of performance in terms of correlation with diacritic error rates. For instance, the model can be used to detect words with high diacritic error rates which tend to have higher uncertainty scores at inference time. On the Tashkeela dataset, the method maintains low Diacritic Error Rate while reducing the amount of visible diacritics on the text by up to 50% with thresholding-based retention.

Uncertainty-driven Partial Diacritization for Arabic Text

Autoregressive language models achieve strong performance across a wide range of natural language processing (NLP) tasks, yet their uncertainty estimates remain poorly understood, particularly during training. Prior work has primarily evaluated calibration and out-of-distribution (OOD) robustness at the final checkpoint, overlooking the dynamics that unfold earlier. We introduce a phase-based framework for tracking uncertainty metrics—including expected calibration error (ECE) and Kullback–Leibler (KL) divergence—across distinct stages of training. Using GPT-2 models trained across multiple random seeds, we find that uncertainty dynamics follow a consistent set of phases: models begin conservative and relatively well calibrated, but later phases introduce a paradoxical decoupling where confidence increases even as calibration worsens, especially under distribution shift. This paradox implies that the final checkpoint is not always the most reliable for deployment and motivates phase-aware strategies such as dynamic checkpoint selection or targeted calibration. Our findings highlight that uncertainty should be understood as a training-dependent property rather than a static one, opening new directions for scaling this framework to larger models, tasks, and distribution shift scenarios.

Phases of Uncertainty: Confidence–Calibration Dynamics in Language Model Training

How do Large Language Models understand moral dimensions compared to humans?

This first comprehensive large-scale Bayesian evaluation of leading language models provides the answer. In contrast to prior approaches based on deterministic ground truth (obtained via majority or inclusion consensus), we obtain the labels by modelling annotators' disagreement to capture both aleatoric uncertainty (inherent human disagreement) and epistemic uncertainty (model domain sensitivity).

We evaluated Claude Sonnet 4, DeepSeek-V3, and Llama 4 Maverick across 250K+ annotations from nearly 700 annotators in 100K+ texts spanning social networks, news, and discussion forums. Our GPU-optimized Bayesian framework processed 1M+ model queries, revealing that AI models generally rank among the top 25\% of annotators in terms of balanced accuracy, substantially better than average humans.

Importantly, we find that AI produces far fewer false negatives than humans, highlighting their sensitive moral detection capabilities.

Beyond Human Judgment: A Bayesian Evaluation of LLMs' Moral Values Understanding

Uncertainty awareness is essential for large language models (LLMs), particularly in safety-critical domains such as medicine where erroneous or hallucinatory outputs can cause harm. Yet most evaluations remain centered on accuracy, offering limited insight into model confidence and its relation to abstention. In this work, we present preliminary experiments that combine conformal prediction with abstention-augmented and perturbed variants of medical QA datasets. Our early results suggest a positive link between uncertainty estimates and abstention decisions, with this effect amplified under higher difficulty and adversarial perturbations. These findings highlight abstention as a practical handle for probing model reliability in medical QA.

Do Large Language Models Know When Not to Answer in Medical QA?

Understanding uncertainty in large language models remains a fundamental challenge, particularly in creative tasks where multiple valid outputs exist. We present a geometric framework using credal sets—convex hulls of probability distributions—to quantify and decompose uncertainty in neural text generation, calibrated against human creative variation. Analyzing 500 creative writing prompts from the \dataset{} dataset with 10 unique human continuations each, we evaluate four language models across five decoding strategies, generating 100,000 stories. Our credal set analysis reveals substantial gaps in capturing human creative variation, with the best model-human calibration reaching only 0.434 (Gemma-2B with temperature 0.7). We decompose total uncertainty into \textit{epistemic} and \textit{aleatoric} components, finding that the choice of decoding strategy contributes 39.4\% to 72.0\% of total epistemic uncertainty. Model scale shows weak correlation with calibration quality and no significant difference exists between base and instruction-tuned models in calibration quality. Our geometric framework provides actionable insights for improving generation systems for human-AI creative alignment. We release our complete experimental framework at \url{https://github.com/EstebanGarces/uncertainHuman}.

The Geometry of Creative Variability: How Credal Sets Expose Calibration Gaps in Language Models

Reliable uncertainty quantification (UQ) is essential for ensuring trustworthy downstream use of large language models, especially when they are deployed in decision-support and other knowledge-intensive applications. Model certainty can be estimated from token logits, with derived probability and entropy values offering insight into performance on the prompt task. However, this approach may be inadequate for probabilistic scenarios, where the probabilities of token outputs are expected to align with the theoretical probabilities of the possible outcomes. We investigate the relationship between token certainty and alignment with theoretical probability distributions in well-defined probabilistic scenarios. Using GPT-4.1 and DeepSeek-Chat, we evaluate model responses to ten prompts involving probability (e.g., roll a six-sided die), both with and without explicit probability cues in the prompt (e.g., roll a fair six-sided die). We measure two dimensions: (1) response validity with respect to scenario constraints, and (2) alignment between token-level output probabilities and theoretical probabilities. Our results indicate that, while both models achieve perfect in-domain response accuracy across all prompt scenarios, their token-level probability and entropy values consistently diverge from the corresponding theoretical distributions.

Certain but not Probable? Differentiating Certainty from Probability in LLM Token Outputs for Probabilistic Scenarios

Model-internal uncertainty metrics like perplexity potentially offer low-cost signals for Machine Translation Quality Estimation (TQE). This paper analyses perplexity in the No Language Left Behind (NLLB) multilingual model. We quantify a significant model-human perplexity gap, where the model is consistently more confident in its own, often literal, machine-generated translation than in diverse, high-quality human versions. We then demonstrate that the utility of perplexity as a TQE signal is highly context-dependent, being strongest for low-resource pairs. Finally, we present an illustrative case study where a flawed translation is refined by providing potentially useful information in a targeted prompt, simulating a knowledge-based repair. We show that as the translation's quality and naturalness improve (a +0.15 COMET score increase), its perplexity also increases, challenging the simple assumption that lower perplexity indicates higher quality and motivating a more nuanced view of uncertainty as signalling a text's departure from rigid translationese.

The Benefits of Being Uncertain: Perplexity as a Signal for Naturalness in Multilingual Machine Translation

Large language models increasingly rely on explicit reasoning chains and can produce multiple plausible responses for a given context. We study the candidate sampler that produces the set of plausible responses contrasting the ancestral (parallel) sampling against two alternatives: enumeration, which asks the model to produce $n$ candidates in one pass, and iterative sampling, which proposes candidates sequentially while conditioning on the currently generated response set. Under matched budgets, we compare these samplers on quality, lexical and computation flow diversity, and efficiency. Our empirical results demonstrate that enumeration and iterative strategies result in higher diversity at comparable quality. Our findings highlight the potential of simple non-independent sampling strategies to improve response diversity without sacrificing generation quality.

Asking a Language Model for Diverse Responses

Natural language generation (NLG) tasks are often subject to inherent variability; e.g. predicting the next word given a context has multiple valid responses, evident when asking multiple humans to complete the task. While having language models (LMs) that are aligned pluralistically, so that they are able to reproduce well the inherent diversity in perspectives of an entire population of interest is clearly beneficial, Ilia and Aziz (2024) show that LMs do not reproduce this type of linguistic variability well. They speculate this inability might stem from the lack of consistent training of LMs with data reflecting this type of inherent variability. As such, we investigate whether training LMs on multiple plausible word continuations per context can improve their ability to reproduce human linguistic variability for next-word prediction. We employ fine-tuning techniques for pre-trained and instruction-tuned models; and demonstrate their potential when fine-tuning GPT-2 and Mistral-7B-IT, using Provo Corpus. Our evaluation, which measures divergence among empirically estimated human and model next-word distributions across contexts before and after fine-tuning, shows that our multi-label fine-tuning improves the LMs’ ability to reproduce linguistic variability; both for contexts that admit higher and lower variability.

Learning to vary: Teaching LMs to reproduce human linguistic variability in next-word prediction

Pixel-based language models aim to solve the vocabulary bottleneck problem in language modeling, but the challenge of uncertainty quantification remains open. The novelty of this work consists of analysing uncertainty and confidence in pixel-based language models across 18 languages and 7 scripts, all part of 3 semantically challenging tasks. This is achieved through several methods such as Monte Carlo Dropout, Transformer Attention, and Ensemble Learning. The results suggest that pixel-based models underestimate uncertainty when reconstructing patches. The uncertainty is also influenced by the script, with Latin languages displaying lower uncertainty. The findings on ensemble learning show better performance when applying hyperparameter tuning during the named entity recognition and question-answering tasks across 16 languages.

Premium content

Downloads

Next from EMNLP 2025

Uncertainty-driven Partial Diacritization for Arabic Text

Stay up to date with the latest Underline news!

PRESENTATIONS

CONFERENCES

COMPANY

RESOURCES