AACL 2025 论文列表

Visual Question Answering (VQA) often requires complex multi-hop reasoning encompassing both vision and language. Despite the remarkable performance of Large Multimodal Models (LMMs) in vision-language tasks, they encounter difficulties when faced with challenging scenarios that require complex reasoning and may be susceptible to object hallucination. This paper introduces a novel framework named Spatial-aware Visual Program Reasoning (SVPR). The primary goal of SVPR is to enhance the alignment between vision and language within LMMs, fostering their multi-hop reasoning abilities and ultimately strengthening their capacity to address complex visual reasoning tasks. We first utilize the strong visual understanding abilities of LMMs to generate scene graphs, facilitating coordination between vision and language at semantic levels. Then, we leverage the in-context learning ability of LMMs to generate visual programs, which guide the question decomposition process. Finally, we employ a program solver to execute the programs and derive the final answer. This process makes our approach both explanatory and robust, providing clear explanations of its reasoning process while ensuring the faithfulness of the answer to the visual input. We evaluate our framework on two challenging multi-hop multimodal VQA datasets and show its effectiveness under zero-shot settings.

Developing robust Natural Language Understanding (NLU) for morphologically rich Dravidian languages like Kannada, Malayalam, Tamil, and Telugu presents significant challenges due to their agglutinative nature and syntactic complexity. In this work, we present the Dravidian NLP Suite tackling five core tasks: Morphological Analysis (MA), POS Tagging (POS), Named Entity Recognition (NER), Dependency Parsing (DEP), and Coreference Resolution (CR), trained for monolingual models and multilingual models. To facilitate this, we present the Dravida dataset, meticulously annotated multilingual corpus for these tasks across all four languages. Our experiments demonstrate that a multilingual model, which utilizes shared linguistic features and cross-lingual patterns inherent to the Dravidian family, consistently outperforms its monolingual counterparts across all tasks. These findings suggest that multilingual learning is an effective approach for enhancing Natural Language Understanding (NLU) capabilities, particularly for languages belonging to the same family. To the best of our knowledge, this is the first work to jointly address all these core tasks on the Dravidian languages.

The Nepali language has distinct linguistic features, especially its complex script (Devanagari script), morphology, and various dialects, which pose a unique challenge for Natural Language Understanding (NLU) tasks. While the Nepali Language Understanding Evaluation (Nep-gLUE) benchmark provides a foundation for evaluating models, it remains limited in scope, covering four tasks. This restricts their utility for comprehensive assessments of Natural Language Processing (NLP) models. To address this limitation, we introduce twelve new datasets, creating a new benchmark, the Nepali Language Understanding Evaluation (NLUE) benchmark for evaluating the performance of models across a diverse set of Natural Language Understanding (NLU) tasks. The added tasks include Single-Sentence Classification, Similarity and Paraphrase Tasks, Natural Language Inference (NLI), and General Masked Evaluation Task (GMET). Through extensive experiments, we demonstrate that existing top models struggle with the added complexity of these tasks. We also find that the best multilingual model outperforms the best monolingual models across most tasks, highlighting the need for more robust solutions tailored to the Nepali language. This expanded benchmark sets a new standard for evaluating, comparing, and advancing models, contributing significantly to the broader goal of advancing NLP research for low-resource languages.

Transformer-based models have revolutionized the field of natural language processing. To understand why they perform so well and to assess their reliability, several studies have focused on questions such as: Which linguistic properties are encoded by these models, and to what extent? How robust are these models in encoding linguistic properties when faced with perturbations in the input text? However, these studies have mainly focused on BERT and the English language. In this paper, we investigate similar questions regarding encoding capability and robustness for 8 linguistic properties across 13 different perturbations in 6 Indic languages, using 9 multilingual Transformer models (7 universal and 2 Indic-specific). To conduct this study, we introduce a novel multilingual benchmark dataset, IndicSentEval, containing approximately ~47K sentences. Our probing analysis of surface, syntactic, and semantic properties reveals that, while almost all multilingual models demonstrate consistent encoding performance for English, surprisingly, they show mixed results for Indic languages. As expected, Indic-specific multilingual models capture linguistic properties in Indic languages better than universal models. Intriguingly, universal models broadly exhibit better robustness compared to Indic-specific models, particularly under perturbations such as dropping both nouns and verbs, dropping only verbs, or keeping only nouns. Overall, this study provides valuable insights into probing and perturbation-specific strengths and weaknesses of popular multilingual Transformer-based models for different Indic languages.

The vast majority of the world’s languages, particularly low-resource and indigenous ones like Bhili, remain critically underserved by modern language technologies. The primary bottleneck is the lack of large-scale corpora required for standard pre-training. To address this gap, we introduce cross-lingual contrastive distillation, a novel and data-efficient, compute-efficient paradigm for creating powerful language models without a massive monolingual corpus. Our method adapts a pre-existing multilingual model (MuRIL) by using a fixed, expert teacher model (HindBERT) to distill semantic knowledge from a related high-resource language (Hindi) via a contrastive objective on a modest parallel corpus. Through comprehensive experiments, we show that our resulting model, GARuD-Bhili, significantly outperforms strong zero-shot and MLM-only baselines on a suite of evaluations, including intrinsic language modeling, downstream sentiment analysis, and cross-lingual benchmarks (Tatoeba, XNLI). Our work presents a generalizable and scalable blueprint for linguistic empowerment, offering a practical pathway to develop robust language technologies for other underserved languages globally.

Translating natural language requirements into Signal Temporal Logic (STL) is essential for safety-critical systems but requires mathematical expertise. We propose a translational grammar mapping Universal Dependencies (UD) structures to STL Operators through 17 theoretically-motivated patterns, evaluated on the NL2TL benchmarking dataset of 7,002 expert-annotated sentence-STL pairs, and an additional cross-domain analysis. We built a parser guided by this grammar to explore the formal deterministic relationship between UDR Compositions and STL Operators, achieving ~99% sentence coverage, ~54% exact matches (and ~97% similarity). Sentence-level regression analyses predict STL statements and STL Operator classes, considering the co-occurance of UDR substructures (UDR components) with an accuracy of more than ~74% and ~81%, respectively. They uncover a new logical grammatical link between temporal NL and formal logic, that is conditioned by the sentence-level context, and provide insights into how linguistic theory unfolds in practice through temporal linguistic expressions.

Self-attention mechanisms have become foundational across modern deep learning architectures. Recent efforts focus on improving their efficiency, particularly for signal processing tasks. The existing approaches employ complex-valued representations for inputs and weights and achieve higher accuracy at the cost of increased model size and inference latency. Dual-numbered algebra offers a promising alternative that allows efficient multiplication and faster inference with the same representational capacity. Inspired by previous studies in the field of hypercomplex neural networks, we introduce a generalized hypercomplex attention block and integrate it into Transformer-based models for EEG classification. Our experiments include adaptation of the hypercomplex models, so that the number of parameters is equal to that of their real-valued counterparts. Across all scenarios, the dual- and complex-numbered models consistently outperform the real ones, demonstrating superior accuracy. This work presents hypercomplex attention as a competitive and computationally efficient strategy with potential value to solve multiple NLP tasks.

Generating accurate and concise textual summaries from multimodal documents is challenging, especially when dealing with visually complex content like scientific posters. We introduce PosterSum, a novel benchmark to advance the development of vision-language models that can understand and summarize scientific posters into research paper abstracts. Our dataset contains 16,305 conference posters paired with their corresponding abstracts as summaries. Each poster is provided in image format and presents diverse visual understanding challenges, such as complex layouts, dense text regions, tables, and figures. We benchmark state-of-the-art Multimodal Large Language Models (MLLMs) on PosterSum and demonstrate that they struggle to accurately interpret and summarize scientific posters. We propose Segment & Summarize, a hierarchical method that outperforms current MLLMs on automated metrics, achieving a 3.14% gain in ROUGE-L. This will serve as a starting point for future research on poster summarization.

Federated large language models (FedLLMs) enable cross-silo collaborative training among institutions while preserving data locality, making them appealing for privacy-sensitive domains such as law, finance, and healthcare. However, the memorization behavior of LLMs can lead to privacy risks that may cause cross-client data leakage. In this work, we study the threat of cross-client data extraction, where a semi-honest participant attempts to recover personally identifiable information (PII) memorized from other clients’ data. We propose three simple yet effective extraction strategies that leverage contextual prefixes from the attacker’s local data, including frequency-based prefix sampling and local fine-tuning to amplify memorization. To evaluate these attacks, we construct a Chinese legal-domain dataset with fine-grained PII annotations consistent with CPIS, GDPR, and CCPA standards, and assess extraction performance using two metrics: coverage and efficiency. Experimental results show that our methods can recover up to 56.6% of victim-exclusive PII, where names, addresses, and birthdays are particularly vulnerable. These findings highlight concrete privacy risks in FedLLMs and establish a benchmark and evaluation framework for future research on privacy-preserving federated learning. Code and data are available at https://github.com/SMILELab-FL/FedPII.

Esports is a competitive sport in which highly skilled players face off in fast-paced video games. Matches consist of intense, moment-by-moment plays that require exceptional technique and strategy. These moments often involve complex interactions, including team fights, positioning, or strategic decisions, which are difficult to interpret without expert explanation. In this study, we set up the task of generating commentary for a specific game moment from multimodal game data consisting of a gameplay screenshot and structured JSON data. Specifically, we construct the first large-scale tri-modal dataset for League of Legends, one of the most popular multiplayer strategy esports titles, and then design evaluation criteria for the task. Using this dataset, we evaluate various large vision language models in generating commentary for a specific moment. We will release the scripts to reconstruct our dataset.

Large language models (LLMs) power modern AI applications, but processing sensitive data on untrusted servers raises privacy concerns. Homomorphic encryption (HE) enables computation on encrypted data for secure inference. However, neural text generation requires decoding methods like argmax and sampling, which are non-polynomial and thus computationally expensive under encryption, creating a significant performance bottleneck. We introduce cutmax, an HE-friendly argmax algorithm that reduces ciphertext operations compared to prior methods, enabling practical greedy decoding under encryption. We also propose the first HE-compatible nucleus (top-p) sampling method, leveraging cutmax for efficient stochastic decoding with provable privacy guarantees. Both techniques are polynomial, supporting efficient inference in privacy-preserving settings. Moreover, their differentiability facilitates gradient-based sequence-level optimization as a polynomial alternative to straight-through estimators. We further provide strong theoretical guarantees for cutmax, proving its convergence via exponential amplification of the gap ratio between the maximum and runner-up elements. Evaluations on realistic LLM outputs show latency reductions of 24\times–35\times over baselines, advancing secure text generation.

Punctuation plays a vital role in structuring meaning, yet current models often struggle to restore it accurately in transcripts of spontaneous speech, especially in the presence of disfluencies such as false starts and backtracking. These limitations hinder the performance of downstream tasks like translation, text-to-speech, summarization, etc. where sentence boundaries are critical for preserving quality. In this work, we introduce Cadence, a generalist punctuation restoration model adapted from a pretrained large language model. Cadence is designed to handle both clean written text and highly spontaneous spoken transcripts. It surpasses the previous state-of-the-art in performance while expanding support from 14 to all 22 Indian languages and English. We conduct a comprehensive analysis of model behavior across punctuation types and language families, identifying persistent challenges under domain shift and with rare punctuation marks. Our findings demonstrate the efficacy of utilizing pretrained language models for multilingual punctuation restoration and highlight Cadence’s practical value for low-resource NLP pipelines at scale.

In-context learning (ICL) has become a prominent paradigm to rapidly customize LLMs to new tasks without fine-tuning. However, despite the empirical evidence of its usefulness, we still do not truly understand how ICL works. In this paper, we compare the behavior of in-context learning with supervised classifiers trained on ICL demonstrations to investigate three research questions: (1) Do LLMs with ICL behave similarly to classifiers trained on the same examples? (2) If so, which classifiers are closer, those based on gradient descent (GD) or those based on k-nearest neighbors (kNN)? (3) When they do not behave similarly, what conditions are associated with differences in behavior? Using text classification as a use case, with six datasets and three LLMs, we observe that LLMs behave similarly to these classifiers when the relevance of demonstrations is high. On average, ICL is closer to kNN than logistic regression, giving empirical evidence that the attention mechanism behaves more similarly to kNN than GD. However, when demonstration relevance is low, LLMs perform better than these classifiers, likely because LLMs can back off to their parametric memory, a luxury these classifiers do not have.

Low-Rank Adaptation (LoRA) has emerged as a widely adopted parameter-efficient fine-tuning (PEFT) approach for language models. By restricting weight updates to a low-rank subspace, LoRA achieves cost-effective finetuning of large, generalist models to more specialized target domains. While LoRA achieves impressive results for a variety of individual downstream tasks, it struggles to capture the diverse expertise needed when presented with a more heterogeneous finetuning corpus. To address this, we propose Expert Weighted Low-Rank Adaptation (EWoRA), a novel LoRA variant that partitions a rank-(r) adapter into (n) independent adapters of rank (r/n). A lightweight “routing” matrix (W_r R^r n) aggregates the outputs of these adapters by learning specialized weights for each context. Experiments show EWoRA improves performance over LoRA when finetuning on heterogeneous data while generally matching or exceeding LoRA performance on individual finetuning tasks under the same low-rank parameter budget.

Large Language Models (LLMs) have shown remarkable reasoning capabilities in mathematical and scientific tasks. To enhance complex reasoning, multi-agent systems have been proposed to harness the collective intelligence of LLM agents. However, existing collaboration structures are either predefined or rely on majority voting or round-table debates, which can suppress correct but less dominant agent contributions. Recent approaches model multi-agent systems as graph networks but optimize purely for agent performance, neglecting the quality of interactions. We hypothesize that effective agent communication is crucial for multi-agent reasoning and that debating quality plays a significant role. To address this, we propose OptAgent, a multi-agent verbal reinforcement learning algorithm that dynamically constructs and refines multi-agent collaboration structures. Our method defines action spaces and a feedback mechanism that evaluates communication robustness and coherence throughout the debate. The final decision is achieved through a majority vote over all the agents. We assess OptAgent on various reasoning tasks, including mathematical reasoning, creative writing, scientific reasoning, and numerical sorting. Results demonstrate that our approach significantly outperforms single-agent prompting methods and state-of-the-art multi-agent frameworks on diverse tasks.

Recent instruction-tuned large language models (LLMs) have demonstrated remarkable performance on various downstream tasks, including named entity recognition (NER). However, previous approaches often generate incorrect predictions, particularly regarding entity boundaries and types. Many of these errors can be corrected to match the ground truth by revising the entity boundaries and/or types. In this paper, we propose a self-correcting instruction tuning approach that simultaneously learns to perform NER and correct errors through natural language instructions. Self-correcting instruction tuning requires only a standard annotated NER dataset. Supervision for self-correction can be automatically generated from error patterns observed in LLMs fine-tuned solely on NER tasks. We conducted extensive experiments on eight NER datasets with two LLMs to validate the effectiveness of the proposed approach. The results demonstrate that the proposed approach enhances NER performance by effectively correcting prediction errors and substantially reducing false positives. We further analyze the self-correction behavior to better understand how the models improve performance.

Knowledge distillation (KD) is a popular method of transferring knowledge from a large “teacher” model to a small “student” model. Previous work has explored various layer-selection strategies (e.g., forward matching and in-order random matching) for intermediate-layer matching in KD, where a student layer is forced to resemble a certain teacher layer. In this work, we revisit such layer-selection strategies and observe an intriguing phenomenon that layer-selection strategy does not matter (much) in intermediate-layer matching—even seemingly nonsensical matching strategies such as reverse matching still result in surprisingly good student performance. We provide an interpretation for this phenomenon by examining the angles between teacher layers viewed from the student’s perspective. Our work sheds light on KD practice, as layer-selection strategies may not be the main focus of KD system design and vanilla forward matching works well in most setups.

As Large Language Models (LLMs) become integral to human-centered applications, understanding their personality-like behaviors is increasingly important for responsible development and deployment. This paper systematically evaluates six LLMs, applying the Big Five Inventory-2 (BFI-2) framework, to assess trait expressions under varying sampling temperatures. We find significant differences across four of the five personality dimensions, with Neuroticism and Extraversion susceptible to temperature adjustments. Further, hierarchical clustering reveals distinct model clusters, suggesting that architectural features may predispose certain models toward stable trait profiles. Taken together, these results offer new insights into the emergence of personality-like patterns in LLMs and provide a new perspective on model tuning, selection, and the ethical governance of AI systems. We share the data and code for this analysis here: https://osf.io/bsvzc/?view_only=6672219bede24b4e875097426dc3fac1

Logical Table-to-Text (LT2T) generation requires models to both verbalize tabular data and reason over it - performing comparisons, aggregations, and causal inference. While many generation tasks struggle with similar analytical demands, LT2T provides a structured perspective on reasoning capabilities in natural language generation. This survey uses LT2T as a lens to focus on reasoning in data-to-text tasks. By focusing narrowly on LT2T, we present a deep taxonomy of methods that inject, structure, or verify reasoning steps, allowing a level of technical granularity missing in broader surveys. We review representative models and evaluation metrics, and highlight how LT2T techniques transfer to general generation challenges involving logic, numeracy, and faithfulness. Our goal is to distill lessons from LT2T that apply more widely, while also guiding future research in table-based reasoning.