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Chain-of-thought (CoT) reasoning has dramatically improved large language model performance on complex tasks. While recent &quot;thinking&#39;&#39; models, like OpenAI&#39;s o1, use substantial inference budgets to further boost performance, this raises concerns about inference efficiency due to potential redundancy. We hypothesize that LLMs have a latent capacity for more concise reasoning, evidenced by shorter, correct reasoning paths in their outputs. To elicit this capacity, we introduce fine-tuning methods leveraging self-generated data from Best-of-N sampling and few-shot conditioning. Our few-shot conditioned best-of-N sampling (FS-BoN) method significantly reduces reasoning length by 30%, or 2.4x more than previous baselines while maintaining accuracy. This implies fine-tuning with curated self-generated data can unlock latent concise reasoning, enabling more efficient inference.

ACL 2025

Self-Training Elicits Concise Reasoning in Large Language Models

concise reasoning

efficient reasoning

chain-of-thought

inference efficiency

self-distillation

compression

large language models

## 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." 

*Message from the General Chair, Dirk Hovy*

EMNLP 2025

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

Chain-of-thought (CoT) reasoning has dramatically improved large language model performance on complex tasks. While recent "thinking'' models, like OpenAI's o1, use substantial inference budgets to further boost performance, this raises concerns about inference efficiency due to potential redundancy. We hypothesize that LLMs have a latent capacity for more concise reasoning, evidenced by shorter, correct reasoning paths in their outputs. To elicit this capacity, we introduce fine-tuning methods leveraging self-generated data from Best-of-N sampling and few-shot conditioning. Our few-shot conditioned best-of-N sampling (FS-BoN) method significantly reduces reasoning length by 30%, or 2.4x more than previous baselines while maintaining accuracy. This implies fine-tuning with curated self-generated data can unlock latent concise reasoning, enabling more efficient inference.

poster

### Welcome to The 63rd Annual Meeting of the Association for Computational Linguistics (ACL 2025)

Message from the General Chair: 
*It is my great pleasure and honor to welcome you to the 63rd Annual Meeting of the Association for Computational Linguistics (ACL 2025), held in beautiful Vienna, Austria, from July 27 to August 1, 2025. ACL2025continues our field’s 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.* 
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Welcome to The 63rd Annual Meeting of the Association for Computational Linguistics (ACL 2025)

Problem-solving therapy (PST) is a structured psychological approach that helps individuals manage stress and resolve personal issues by guiding them through problem identification, solution brainstorming, decision-making, and outcome evaluation. As mental health care increasingly adopts technologies like chatbots and large language models (LLMs), it is important to thoroughly understand how each session of PST is conducted before attempting to auto mate it. We developed a comprehensive framework for PST annotation using established PST Core Strategies and a set of novel Facilitative Strategies to analyze a corpus of real-world therapy transcripts to determine which strategies are most prevalent. Using various LLM and transformer-based models, we found that GPT-4o outperformed all models, achieving the highest accuracy (0.76) in identifying all strategies. To gain deeper insights, we examined how strategies are applied by analyzing Therapeutic Dynamics (autonomy, self-disclosure, and metaphor), and linguistic patterns within our labeled data. Our research highlights LLMs’ potential to automate therapy dialogue analysis, offering a scalable tool for mental health interventions. Our framework enhances PST by improving accessibility, effectiveness, and personalized support for therapists.

From Conversation to Automation: Leveraging LLMs for Problem-Solving Therapy Analysis

Large language model (LLM) parameters store massive amounts of pre-training knowledge, but it is unclear how to continually update them to reflect changes in the real world. Both dataset and methodology works in existing literature focus on the entity-substitution framework which does not capture the breadth of complex real world updates. In this paper, we first introduce Knowledge Update Playground (KUP) to automatically construct a training corpus with realistic and complex updates to study this problems. Next, we introduce a novel approach, memory recall training (MRT), that trains the model to explicitly surface and condition on "recalled" knowledge both at train and test time. Our results show that the KUP benchmark is challenging for existing continued pre-training (CPT) approaches; LLMs after CPT still prefer outdated knowledge >40% of the time. Using our proposed MRT training approach significantly improves performance across datasets and evaluation settings (58.9 -> 71.0 for LLaMA-3.1-8B). Overall, we show that our KUP dataset, particularly an indirect probing evaluation setting, serves as a challenging testbed to facilitate future research.

Memorization vs. Reasoning: Updating LLMs with New Knowledge

As AI advances in text generation, human trust in AI generated content remains constrained by biases that go beyond concerns of accuracy. This study explores how bias shapes the perception of AI versus human generated content. Through three experiments involving text rephrasing, news article summarization, and persuasive writing, we investigated how human raters respond to labeled and unlabeled content. While the raters could not differentiate the two types of texts in the blind test, they overwhelmingly favored content labeled as "Human Generated," over those labeled "AI Generated," by a preference score of over 30%. We observed the same pattern even when the labels were deliberately swapped. This human bias against AI has broader societal and cognitive implications, as it undervalues AI performance. This study highlights the limitations of human judgment in interacting with AI and offers a foundation for improving human-AI collaboration, especially in creative fields.

Human Bias in the Face of AI: The Role of Human Judgement in AI Generated Text Evaluation

This study explores a novel approach to enhance the performance of Large Language Models (LLMs) through the optimization of input data within prompts. While previous research has primarily focused on refining instruction components and augmenting input data with in-context examples, our work investigates the potential benefits of optimizing the input data itself. We introduce a two-pronged strategy for input data optimization: content engineering and structural reformulation. Content engineering involves imputing missing values, removing irrelevant attributes, and enriching profiles by generating additional information inferred from existing attributes. Subsequent to content engineering, structural reformulation is applied to optimize the presentation of the modified content to LLMs, given their sensitivity to input format. Our findings suggest that these optimizations can significantly improve the performance of LLMs in various tasks, offering a promising avenue for future research in prompt engineering. The source code is available at https://github.com/glin2229/Automatic-Data-Optimization.

ADO: Automatic Data Optimization for Inputs in LLM Prompts

Internal world models (WMs) enable agents to understand the world's state and predict transitions, serving as the basis for advanced deliberative reasoning. Recent large Vision-Language Models (VLMs), such as GPT-4o and Gemini, exhibit potential as general-purpose WMs. While the latest studies have evaluated and shown limitations in specific capabilities such as visual understanding, a systematic evaluation of VLMs' fundamental WM abilities remains absent. Drawing on comparative psychology and cognitive science, we propose a two-stage framework that assesses Perception (visual, spatial, temporal, quantitative, and motion) and Prediction (mechanistic simulation, transitive inference, compositional inference) to provide an atomic evaluation of VLMs as WMs. Guided by this framework, we introduce WM-ABench, a large-scale benchmark comprising 23 fine-grained evaluation dimensions across 6 diverse simulated environments with controlled counterfactual simulations. Through 517 controlled experiments on 11 latest commercial and open-source VLMs, we find that these models exhibit striking limitations in basic world model abilities. For instance, all models perform at near-random accuracy when distinguishing motion trajectories. Additionally, they lack disentangled understanding---e.g., they tend to believe blue objects move faster than green ones. More rich results and analyses reveal significant gaps between VLMs and human-level world modeling.

Do Vision-Language Models Have Internal World Models? Towards an Atomic Evaluation

Investigating bias in large language models (LLMs) is crucial for developing trustworthy AI. While prompt-based through prompt engineering is common, its effectiveness relies on the assumption that models inherently understand biases. Our study systematically analyzed this assumption using the BBQ and StereoSet benchmarks on both open-source models as well as commercial GPT model. Experimental results indicate that prompt-based is often superficial; for instance, the Llama2-7B-Chat model misclassified over 90% of unbiased content as biased, despite achieving high accuracy in identifying bias issues on the BBQ dataset. Additionally, specific evaluation and question settings in bias benchmarks often lead LLMs to choose "evasive answers", disregarding the core of the question and the relevance of the response to the context. Moreover, the apparent success of previous methods may stem from flawed evaluation metrics. Our research highlights a potential "false prosperity" in prompt-base efforts and emphasizes the need to rethink bias evaluation metrics to ensure truly trustworthy AI. We will release our data and code upon acceptance.

Rethinking Prompt-based Debiasing in Large Language Model

Large language models (LLMs) demonstrate impressive results in natural language processing tasks, but require a significant amount of computational and memory resources. Structured matrix representations is a promising way for reducing the number of parameters of these models. However, it seems unrealistic to expect that weight matrices of pretrained models can be accurately represented by structured matrices without any fine-tuning. To overcome this issue, we utilize the fact that LLM output is invariant under certain orthogonal transformations of weight matrices. This insight can be leveraged to identify transformations that significantly improve the compressibility of weights within the structured classes. The proposed approach is applicable to various types of structured matrices that support efficient projection operations.

ProcrustesGPT: Compressing LLMs with Structured Matrices and Orthogonal Transformations

Lightweight Large Language Models (LwLLMs) are reduced-parameter, optimized models designed to run efficiently on consumer-grade hardware, offering significant advantages in resource efficiency, cost-effectiveness, and data privacy. However, these models often struggle with limited inference and reasoning capabilities, which restrict their performance on complex tasks and limit their practical applicability. Moreover, existing prompt optimization methods typically rely on extensive manual effort or the meta-cognitive abilities of state-of-the-art LLMs, making them less effective for LwLLMs.

To address these challenges, we introduce DeBoP, a new Direct Behavior Optimization Paradigm, original from the Chain-of-Thought (CoT) prompting technique. Unlike CoT Prompting, DeBoP is an automatic optimization method, which focuses on the optimization directly on the behavior of LwLLMs. In particular, DeBoP transforms the optimization of complex prompts into the optimization of discrete, quantifiable execution sequences using a gradient-free Monte Carlo Tree Search. We evaluate DeBoP on seven challenging tasks where state-of-the-art LLMs excel but LwLLMs generally underperform. Experimental results demonstrate that DeBoP significantly outperforms recent prompt optimization methods on most tasks. In particular, DeBoP-optimized LwLLMs surpass GPT-3.5 on most tasks while reducing computational time by approximately 60% compared to other automatic prompt optimization methods.

Direct Behavior Optimization: Unlocking the Potential of Lightweight LLMs

A NOTAM or NOtice To AirMen is a crucial notice for different aviation stakeholders, particularly flight crews. It delivers essential notifications about abnormal conditions of Aviation System components such as changes to facilities, hazards, service, procedure that are not known far enough in advance to be publicized through other means. NOTAM messages are short, contain acronyms, and look cryptic in most of the cases. Writing and understanding these messages put heavy cognitive load on its end users. In this work, we take up the task of translating NOTAMs into English natural language using LLMs. Since NOTAMs do not adhere to English grammar rules and have their own decoding rules, large language models (LLMs) cannot translate them without effective prompting. In this paper, we develop a framework to come up with effective prompts to achieve the translations. Our approach uses context-aware semantic prompting techniques, paired with domain-specific rules, to improve the accuracy and clarity of translations. The framework is evaluated using comprehensive experiments (6 LLMs of varying sizes, and with 5 different prompting setups for each) and eight evaluation metrics measuring different aspects of the translation. The results demonstrate that our methodology can produce clear translations that accurately convey the information contained in NOTAMs.

Semantics-aware prompting for translating NOtices To AirMen

Vision-language models (VLMs) integrate textual and visual information, enabling the model to process visual inputs and leverage visual information to generate predictions. Such models are demanding for tasks such as visual question answering, image captioning and visual grounding. However, some recent work found that %visual information is not fully utilized by language models. That is, VLMs often rely heavily on textual information, ignoring visual information, but are still able to achieve competitive performance in vision-language (VL) tasks. This survey reviews modality collapse analysis work to provide insights into the reason for this unintended behaviour. It also reviews probing studies for fine-grained vision-language understanding, presenting current findings on information encoded in VL representations and highlight potential directions for future research.

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From Conversation to Automation: Leveraging LLMs for Problem-Solving Therapy Analysis

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