Papers by Hao Tan
UAQFact: Evaluating Factual Knowledge Utilization of LLMs on Unanswerable Questions (2025.findings-acl)
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| Challenge: | Existing datasets to assess LLMs' performance on unanswerable questions lack factual knowledge support. |
| Approach: | They propose a bilingual unanswerable question dataset with auxiliary factual knowledge created from a Knowledge Graph and two new tasks to measure LLMs' ability to utilize internal and external factual information. |
| Outcome: | The proposed datasets show that LLMs do not consistently perform well even when they have factual knowledge stored. |
Tiny-Attention Adapter: Contexts Are More Important Than the Number of Parameters (2022.emnlp-main)
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| Challenge: | Adapter-tuning is a paradigm that transfers a pretrained language model to downstream tasks . Previously proposed adapters are all feed-forward neural networks . |
| Approach: | They propose to use tiny-attention attention with extremely small per-head dimensionality as adapters to modify hidden states at each position . they propose to average multiple attention heads' weights during deployment to reduce its inference computation cost. |
| Outcome: | The proposed adapter outperforms other adapter-tuning methods on the GLUE benchmark . it uses attention with extremely small per-head dimensionality to modify hidden states . |
The Curse of Performance Instability in Analysis Datasets: Consequences, Source, and Suggestions (2020.emnlp-main)
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| Challenge: | Neural network models have significantly pushed forward performance on natural language processing benchmarks with the development of largescale language model pre-training. |
| Approach: | They find that models on natural language inference and reading comprehension are unstable . they propose to use a model-selection routine to analyze the model's instability . |
| Outcome: | The proposed models can perform poorly on two language-related tasks, the authors show . they also show that the model selection routine is unstable, and that it is not reliable . |
Multimodal Needle in a Haystack: Benchmarking Long-Context Capability of Multimodal Large Language Models (2025.naacl-long)
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Hengyi Wang, Haizhou Shi, Shiwei Tan, Weiyi Qin, Wenyuan Wang, Tunyu Zhang, Akshay Nambi, Tanuja Ganu, Hao Wang
| Challenge: | Multimodal Large Language Models have shown significant promise in various applications, but a comprehensive evaluation of their long-context capabilities remains underexplored. |
| Approach: | They propose a benchmark to assess the long-context capabilities of multimodal large language models. |
| Outcome: | The proposed benchmark compared MLLMs with API-based and open-source models in a long-context scenario. |
LXMERT: Learning Cross-Modality Encoder Representations from Transformers (D19-1)
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| Challenge: | Existing models with better representations of visual content and language have been developed for visual-content understanding. |
| Approach: | They propose a framework to learn vision-and-language connections from Transformers models . they pre-train a large-scale Transformer model with large amounts of image-and sentence pairs . |
| Outcome: | The proposed model improves state-of-the-art on two visual-reasoning tasks by 22% . the proposed model is based on a large-scale Transformer model with three encoders . |
Bilingual Dictionary Based Neural Machine Translation without Using Parallel Sentences (2020.acl-main)
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| Challenge: | a monolingual speaker can learn to translate by looking up a bilingual dictionary . a novel task of machine translation (MT) is based on no parallel sentences but can refer to a ground-truth bilingual dictionary and large-scale monolingual corpora. |
| Approach: | They propose a task of machine translation that uses a bilingual dictionary and large-scale monolingual corpora to translate a monolingual speaker. |
| Outcome: | The proposed task is based on a bilingual dictionary and large scale monolingual corpora, while being independent on parallel sentences. |
Object Ordering with Bidirectional Matchings for Visual Reasoning (N18-2)
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| Challenge: | et al. (2016) proposed a novel end-to-end neural model for visual reasoning with compositional natural language instructions. |
| Approach: | They propose an end-to-end neural model for a visual reasoning task based on a newly-released Cornell dataset . they use joint bidirectional attention to build a two-way conditioning between visual information and language phrases . then they use an RL-based pointer network to sort and process the varying number of unordered objects in each image and pool over the three decisions . |
| Outcome: | The proposed model achieves 4-6% absolute improvements over the state-of-the-art model on the NLVR dataset. |
Leibniz: Theory-of-Mind Driven Neuro-Symbolic Logical Reasoning via Multi-Agent Collaboration (2026.acl-long)
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| Challenge: | Existing methods for logical reasoning with large language models suffer from insufficient rule semantic grounding and weak rule application mechanisms. |
| Approach: | They propose a theory-of-mind driven neuro-symbolic reasoning framework that integrates natural language and symbolic representations throughout the reasoning process. |
| Outcome: | The proposed model surpasses state-of-the-art models in reasoning accuracy and flexibility. |
TabPrompt: Graph-based Pre-training and Prompting for Few-shot Table Understanding (2023.findings-emnlp)
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| Challenge: | Existing methods of Table Understanding (TU) focus on the textual content within the tabular data, disregarding the topological information of the table. |
| Approach: | They propose a framework that uses tabs to understand tabular data without ignoring the topological information of the table. |
| Outcome: | The proposed framework outperforms baselines in few-shot table understanding tasks. |
Vokenization: Improving Language Understanding with Contextualized, Visual-Grounded Supervision (2020.emnlp-main)
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| Challenge: | Existing language pretraining frameworks only take the language context as selfsupervision . current frameworks do not take grounding information from the external visual world . |
| Approach: | They propose a visually-supervised language model that extrapolates multimodal alignments to language-only data by contextually mapping language tokens to related images. |
| Outcome: | The proposed model improves on multiple pure-language tasks. |
Expressing Visual Relationships via Language (P19-1)
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| Challenge: | Current studies on image captioning focus on single image, but there are no effective models for generating relational captions for two images. |
| Approach: | They propose a language-guided image editing dataset that contains real image pairs with corresponding editing instructions. |
| Outcome: | The proposed model outperforms baseline and existing methods on two datasets. |
Calibrating Inference Time Alignment with Sequence-level Risk Accumulation (2026.acl-long)
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| Challenge: | Existing approaches to decode large language models (LLMs) often over-reject benign information, limiting their generalizability in real-world scenarios where harmful and benign information coexist. |
| Approach: | They propose a framework to regulate decoding alignments for Large Language Models (LLMs) they employ a reward-guided branch decoding paradigm to incorporate safety awareness during generation. |
| Outcome: | The proposed framework achieves superior performance on four attack benchmarks and two neutral datasets. |
Improving Cross-Modal Alignment in Vision Language Navigation via Syntactic Information (2021.naacl-main)
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| Challenge: | Existing vision language navigation tasks require soft attention over words to locate instructions . a new approach uses syntax information to ground instructions with visual information . |
| Approach: | They propose a vision language navigation agent that utilizes syntax information to enhance alignment between the instruction and the current visual scenes. |
| Outcome: | The proposed agent outperforms the baseline model that does not use syntax information on the Room-to-Room dataset, especially in the unseen environment. |
Variational Language Concepts for Interpreting Foundation Language Models (2024.findings-emnlp)
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| Challenge: | Foundation Language Models (FLMs) have achieved remarkable success in natural language processing. |
| Approach: | They propose a variational Bayesian framework to provide word-level interpretations for FLMs . they propose valc to find optimal language concepts to interpret FLM predictions . |
| Outcome: | Empirical results show that the proposed framework can provide conceptual interpretations for foundation language models. |
PRA-RAG: Provably Robust Aggregation in Retrieval-Augmented Generation against Retrieval Corruption (2026.findings-acl)
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Xue Tan, Yi Zheng, Chang Huo, Yunruo Zhang, Yu Liu, Hao Luan, Zhuyang Yu, Jun Dai, Xiaoyan Sun, Ping Chen
| Challenge: | Existing defense mechanisms lack theoretical robustness guarantees and perform unreliably when the LLM has limited knowledge of the retrieved content. |
| Approach: | They propose a provably robust retrieval aggregation algorithm designed to defend against poisoning attacks on retrieved texts. |
| Outcome: | Experiments show that PRA-RAG reduces the attack success rate to as low as 1% while maintaining an accuracy of 71%, significantly outperforming representative state-of-the-art (SOTA) methods. |
Rejection-to-Acceptance Transition: Model Editing-Based Jailbreak Backdoor Injection Not Limited to Few Output Tokens (2026.findings-acl)
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Shiji Yang, Min Cai, Hao Xiong, Congyao Mei, Haodong Zou, Shicheng Tan, Jie Chen, Fulan Qian, Shu Zhao
| Challenge: | Existing methods for jailbreaking LLMs are implemented by binding backdoors to predefined phrases as first few output tokens, inducing the LLM’s next-token prediction to produce continuous responses. |
| Approach: | They propose a model editing-based jailbreak backdoor attack that hijacks LLM representations into a acceptance domain rather than binding to a few output tokens. |
| Outcome: | The proposed model editing method outperforms existing methods, showing stronger jailbreak capabilities across LLMs and datasets. |
BertNet: Harvesting Knowledge Graphs with Arbitrary Relations from Pretrained Language Models (2023.findings-acl)
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| Challenge: | Existing methods to construct knowledge graphs are limited to a small set of relations due to manual cost or restrictions in text corpus. |
| Approach: | They propose to automatically construct knowledge graphs (KGs) of diverse new relations from pretrained language models that accept knowledge queries with prompts. |
| Outcome: | The proposed framework extracts knowledge of over 400 new relations from pretrained language models, including RoBERTaNet, with minimal input of a relation definition and a few shot of example entity pairs. |
Tree-CoT-RT: An Explainable Multi-Path Tree-Guided Chain-of-Thought and Reinforcement Learning Framework for Aspect Sentiment Quad Prediction (2026.findings-acl)
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Hao Zhang, Jiahao Wang, Zhenke Duan, Xin Yin, Haichuan Hu, Hualong Chen, null Suyi, Congqing He, Yike Tan, Yu-N Cheah
| Challenge: | Existing methods lack explainability and generalization, making it difficult to justify inference decisions and detect implicit sentiment across domains and varied expression patterns. |
| Approach: | They propose an explainable multi-path tree-guided chain-of-thought framework specifically designed for ASQP. |
| Outcome: | Experiments on benchmark datasets show that Tree-CoT-RT outperforms baselines. |
MAF: Multimodal Alignment Framework for Weakly-Supervised Phrase Grounding (2020.emnlp-main)
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| Challenge: | Existing work on phrase localization uses caption-image datasets as weak supervision . existing work on supervised phrase localisation uses a large-scale annotated dataset . |
| Approach: | They develop a multimodal alignment framework to leverage more widely available caption-image datasets to model phrase relevance. |
| Outcome: | The proposed model improves on the widely-adopted Flickr30k dataset . it also improves the previous best unsupervised result by 5.56% . |
ArraMon: A Joint Navigation-Assembly Instruction Interpretation Task in Dynamic Environments (2020.findings-emnlp)
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| Challenge: | embodied agents are expected to perform specific tasks after reaching the destination . a novel vision-and-language navigation task is designed to support this task . |
| Approach: | They combine vision-and-language navigation, assembling objects and object referring expression comprehension to create a joint navigation-and assembly task. |
| Outcome: | The proposed task is based on vision-and-language navigation and assembly . it uses human-written navigation and assembling instructions and ground truth trajectories . the large model-human performance gap shows that the task is challenging and wide scope for future work. |
CLEAR: Improving Vision-Language Navigation with Cross-Lingual, Environment-Agnostic Representations (2022.findings-naacl)
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| Challenge: | Using multilingual instructions to learn a better cross-lingual representation is challenging for multilingual agents. |
| Approach: | They propose to use multilingual instructions to learn a shared cross-lingual language representation for the three languages in a Room-Across-Room dataset. |
| Outcome: | The proposed model improves on the room-Across-room and vision-and-dialogue navigation tasks by maximizing similarity between semantically aligned image pairs from different environments. |
Learning to Navigate Unseen Environments: Back Translation with Environmental Dropout (N19-1)
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| Challenge: | Existing approaches perform significantly worse in unseen environments compared to seen ones. |
| Approach: | They propose to use a ‘environmental dropout’ method to generate unseen triplets to generate new paths and instructions to generalize the agent. |
| Outcome: | The proposed agent outperforms the state-of-the-art approaches on the private unseen test set and is ranked top on the leaderboard. |
RevPRAG: Revealing Poisoning Attacks in Retrieval-Augmented Generation through LLM Activation Analysis (2025.findings-emnlp)
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| Challenge: | Retrieval-Augmented Generation (RAG) enriches the input to LLMs by retrieving information from the relevant knowledge database. |
| Approach: | They propose to use a knowledge database to enrich the input of LLMs by retrieving information from the relevant knowledge database. |
| Outcome: | The proposed approach can achieve 98% true positive rate while maintaining a false positive rate close to 1%. |