India

In many real-world settings like journalism, law, medicine, and science communication, information is passed from one person or system to another through multiple rounds of summarization or rewriting. This process, known as multi-hop information transfer, also happens increasingly in workflows involving large language models (LLMs). But while summarization models and factuality metrics have improved, we still don’t fully understand how meaning and factual accuracy hold up across long chains of transformations, especially when both humans and LLMs are involved.

In this paper, we take a fresh look at this problem by combining insights from cognitive science (Bartlett’s serial reproduction) and information theory (Shannon’s noisy-channel model). We build a new dataset of 700 five-step transmission chains that include human-only, LLM-only, mixed human-LLM, and cross-LLM settings across a wide range of source texts. To track how meaning degrades, we introduce three new metrics: Information Degradation Rate (IDR) for semantic drift, Meaning Preservation Entropy (MPE) for uncertainty in factual content, and Cascaded Hallucination Propagation Index (CHPI) for how hallucinations accumulate over time. Our findings reveal that hybrid chains behave asymmetrically. When a human summary is refined by a language model, the final output tends to preserve meaning well, suggesting that models can improve upon human-written summaries.  The code and data will be available at : https://github.com/transtrace6/TransTrace.git.

IJCNLP-AACL 2025

Who Remembers What? Tracing Information Fidelity in Human-AI Chains

hallucination propagation

information degradation

semantic fidelity

human–llm collaboration

multi-hop summarization

It is my great pleasure and honor to welcome you to the 64th Annual Meeting of the Association for Computational Linguistics (ACL 2026), held in San Diego, California, USA, July 2–7, 2026. ACL 2026 continues our fields tradition of excellence in scholarship, innovation, and inclusivity, and I am deeply grateful to the many volunteers who have worked tirelessly to bring this event to life.

It is exciting to see the many developments in the field reflected at our conference, such as the advancement of large language models (born out of our community) into many application directions. This is not without challenges, partly due to unsolved problems, and partly due to misuse of the technology. All this is reflected well at ACL 2026. The conference also reflects that the field is not only about advancing technology, but also the science of fundamentally understanding language and how it is use by many different speaker communities. 
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ACL 2026

The 64th Annual Meeting of the Association for Computational Linguistics (ACL 2026) will take place in San Diego, California, from July 2 - 7, 2026.

technical paper

### Welcome to IJCNLP-AACL 2025! 
 It is a great honor to host this joint conference in Mumbai, India, from December 20 to 24, 2025. The joint conferences of IJCNLP and AACL are organized with alternating leadership in the Asia-Pacific region. The event is run by the Asian Federation of Natural Language Processing (AFNLP) in odd years, and by AACL in even years, while it is organized solely by ACL when the annual ACL meeting is held in the region. This year, the conference is primarily organized by AFNLP. 
*Kentaro Inui
MBZUAI, UAE
General Chair, IJCNLP-AACL 2025* 
Read full message and download the Conference Handbook [**here**](https://drive.google.com/file/d/1UTwxkAqSqI-GAoJC3wE1zZt5VP1Y8GX0/view?usp=sharing).

The 14th IJCNLP & 4th AACL will be held in Mumbai, India from December 20th to December 24th, 2025.

This paper investigates the relationship between large language models’ (LLMs) ability to recognize repetitive input patterns and their performance on in-context learning (ICL). In contrast to prior work that has primarily focused on attention heads, we examine this relationship from the perspective of skill neurons, specifically repetition neurons. Our experiments reveal that the impact of these neurons on ICL performance varies depending on the depth of the layer in which they reside. By comparing the effects of repetition neurons and induction heads, we further identify strategies for reducing repetitive outputs while maintaining strong ICL capabilities.

Understanding and Controlling Repetition Neurons and Induction Heads in In-Context Learning

Instruction-tuning plays a vital role in enhancing the task-solving abilities of large language models (LLMs), improving their usability in generating helpful responses on various tasks. However, previous work has demonstrated that they are sensitive to minor variations in instruction phrasing. In this paper, we explore whether introducing perturbations in instruction-tuning data can enhance LLMs' resistance against noisy instructions. We focus on how instruction-tuning with perturbations, such as removing stop words or shuffling words, affects LLMs' performance on the original and perturbed versions of widely-used benchmarks (MMLU, BBH, GSM8K). We further assess learning dynamics and potential shifts in model behavior. Surprisingly, our results suggest that instruction-tuning on perturbed instructions can, in some cases, improve downstream performance. These findings highlight the importance of including perturbed instructions in instruction-tuning, which can make LLMs more resilient to noisy user inputs.

Fine-Tuning on Noisy Instructions: Effects on Generalization and Performance

As the adoption of large language models (LLMs) continues to grow, the risk of sensitive data leakage from their training datasets has become a critical concern. This study proposes a novel method for encrypting training data using a polyalphabetic substitution cipher. This approach prevents the model from learning sensitive information while allowing it to capture abstract linguistic patterns. We pre-trained a Llama 3 model (551M parameters) using approximately 7.5 billion tokens of encrypted data and subsequently conducted continual pre-training with another 2.5 billion tokens of plaintext data. The effectiveness of the model was evaluated by comparing its downstream task performance with a model trained solely on plaintext data. In addition, we evaluated the risk of sensitive data leakage through name reconstruction, true-prefix and data extraction attacks. These results demonstrate the potential of our approach to balance data security with model performance.

Crypto-LLM: Two-Stage Language Model Pre-training with Ciphered and Natural Language Data

Test-time scaling has emerged as an effective approach for improving language model performance by utilizing additional compute at inference time. Recent studies have shown that overriding end-of-thinking tokens (e.g., replacing "\</think>" with "Wait") can extend reasoning steps and improve accuracy. In this work, we explore whether a dedicated continue-thinking token can be learned to trigger extended reasoning. We augment distilled versions of DeepSeek-R1 with a single learned "<|continue-thinking|>" token, training only its embedding via reinforcement learning while keeping the model weights frozen. Our experiments show that this learned token achieves improved accuracy on standard math benchmarks compared to both the baseline model and a test-time scaling approach that uses a fixed token (e.g., "Wait") for budget forcing. In particular, we observe that in cases where the fixed-token approach enhances the base model's accuracy, our method achieves a markedly greater improvement. For example, on the GSM8K benchmark, the fixed-token approach yields a 1.3% absolute improvement in accuracy, whereas our learned-token method achieves a 4.2% improvement over the base model that does not use budget forcing.

Learning a Continue-Thinking Token for Enhanced Test-Time Scaling

Large Language Models (LLMs) demonstrate remarkable multilingual capabilities, yet it remains unclear whether they are truly multicultural. Do they merely process different languages, or can they genuinely comprehend the unique cultural contexts embedded within them? This study investigates this critical question by examining whether LLM's perception of emotion and empathy differs across linguistic and cultural boundaries. To facilitate this, we introduce the Korean Empathetic Dialogues (KoED), a benchmark extending the English-based EmpatheticDialogues (ED) dataset. Moving beyond direct translation, we meticulously reconstructed dialogues specifically selected for their potential for cultural adaptation, aligning them with Korean emotional nuances and incorporating key cultural concepts like ‘jeong’ and ‘han’ that lack direct English equivalents. Our cross-cultural evaluation of leading multilingual LLMs reveals a significant "cultural empathy gap": models consistently underperform on KoED compared to ED, struggling especially with uniquely Korean emotional expressions. Notably, the Korean-centric model, EXAONE, exhibits significantly higher cultural appropriateness. This result provides compelling evidence that aligns with the "data provenance effect", suggesting that the cultural alignment of pre-training data is a critical factor for genuine empathetic communication. These findings demonstrate that current LLMs have cultural blind spots and underscore the necessity of benchmarks like KoED to move beyond simple linguistic fluency towards truly culturally adaptive AI systems.

Multilingual, Not Multicultural: Uncovering the Cultural Empathy Gap in LLMs through a Comparative Empathetic Dialogue Benchmark

Recent advances in large language models (LLMs) such as GPT-4o offer the potential for enhancing AI-driven robotic interactions, but their effectiveness in mobile tour guidance remains unexplored. This study investigates the differences between human-operated and AI-driven guidance at an aquarium using Teleco, a teleoperated mobile robot, in a real-world field experiment. A total of 277 guidance sessions were collected under two modes: human-operated, where the operator controlled all dialogue, actions, and movement, and AI-driven, where GPT-4o generated responses while the operator only controlled the robot's actions and movement. Our results indicate that human-operated guidance places greater emphasis on visitor movement, spatial positioning during observation guidance, and empathetic expressions, whereas AI-driven guidance promotes conversational engagement by frequently prompting visitors to ask questions. In addition, we found that user behaviors, including users' gaze patterns and vocabulary richness, also serve as valuable indicators reflecting their overall experience during guidance interactions. Furthermore, empathetic expression is recognized as the key differentiating factor between the two guidance modes, significantly influencing users' overall experience.

A Comparative Study of Human-operated and AI-driven Guidance with a Teleoperated Mobile Robot

Large language models (LLMs) are increasingly widely used as critical components of knowledge retrieval systems and agentic systems. These systems can benefit from knowledge-seeking capabilities of LLMs, in other words, curiosity. However, this capability has not been evaluated quantitatively. Towards bridging this gap, we propose an evaluation framework, CDQG (Curiosity-Driven Question Generation). The CDQG task prompts LLMs to generate questions about a statement introducing scientific knowledge, simulating a curious person when facing the statement for the first time. The CDQG dataset contains 1,988 statements including physics, chemistry, and mathematics with distinct levels of difficulty, general knowledge statements, and intentionally erroneous statements. We score the qualities of the questions generated by LLMs along multiple dimensions. These scores are validated by rigorous controlled ablation studies and human evaluations. While large models like GPT-4 and Mistral 8x7b can generate highly coherent and relevant questions, the smaller Phi-2 model is equally or more effective. This indicates that size does not solely determine a model’s knowledge acquisition potential. CDQG quantifies a critical model capability, and opens up research opportunities for developing future knowledge retrieval systems driven by LLMs.

What Would You Ask When You First Saw a2+b2=c2? Evaluating LLM on Curiosity-Driven Question Generation

Traditional dialogue summarization primarily focuses on dialogue content, assuming it comprises adequate information for a clear summary. However, this assumption often fails for discussions grounded in shared background, where participants frequently omit context and use implicit references. This results in summaries that are confusing to readers unfamiliar with the background. To address this, we introduce Knowledge-Grounded Discussion Summarization (KGDS), a novel task that produces a supplementary background summary for context and a clear opinion summary with clarified references. To facilitate research, we construct the first KGDS benchmark, featuring news-discussion pairs and expert-created multi-granularity gold annotations for evaluating sub-summaries. We also propose a novel hierarchical evaluation framework with fine-grained and interpretable metrics. Our extensive evaluation of 12 advanced large language models (LLMs) reveals that KGDS remains a significant challenge. The models frequently miss key facts and retain irrelevant ones in background summarization, and often fail to resolve implicit references in opinion summary integration.

What Are They Talking About? A Benchmark of Knowledge-Grounded Discussion Summarization

Trustworthy evaluations of dangerous capabilities are increasingly crucial for determining whether an AI system is safe to deploy. One empirically demonstrated threat is $\textit{sandbagging}$—the strategic underperformance on evaluations by AI models or their developers. A promising defense is to monitor a model's chain-of-thought (CoT) reasoning, as this could reveal its intentions and plans. In this work, we measure the ability of models to sandbag on dangerous capability evaluations against a CoT monitor by prompting them to sandbag while being either monitor-oblivious or monitor-aware. We show that both frontier models and small open-sourced models can $\textit{covertly}$ sandbag against CoT monitoring 0-shot without hints. However, they cannot yet do so reliably: they bypass the monitor 16-36\% of the time when monitor-aware, conditioned on sandbagging successfully. We qualitatively analyzed the uncaught CoTs to understand $\textit{why}$ the monitor failed. We reveal a rich attack surface for CoT monitoring and contribute five covert sandbagging policies generated by models. These results inform potential failure modes of CoT monitoring and may help build more diverse sandbagging model organisms.

LLMs Can Covertly Sandbag on Capability Evaluations Against Chain-of-Thought Monitoring

Audio Large Language Models (AudioLLMs) have achieved strong results in semantic tasks like speech recognition and translation, but remain limited in modeling paralinguistic cues such as emotion. Existing approaches often treat emotion understanding as a classification problem, offering little insight into the underlying rationale behind predictions. In this work, we explore emotion reasoning, a strategy that leverages the generative capabilities of AudioLLMs to enhance emotion recognition by producing semantically aligned, evidence-grounded explanations. To support this in multitask AudioLLMs, we introduce a unified framework combining reasoning-augmented data supervision, dual-encoder architecture, and task-alternating training. This approach enables AudioLLMs to effectively learn different tasks while incorporating emotional reasoning. Experiments on IEMOCAP and MELD show that our approach not only improves emotion prediction accuracy but also enhances the coherence and evidential grounding of the generated responses. Experiments on two out-of-domain datasets demonstrate the generalization capabilities of the resulting model.

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Understanding and Controlling Repetition Neurons and Induction Heads in In-Context Learning

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