Jizhong Han


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Uncertainty-Aware Cross-Modal Alignment for Hate Speech Detection
Chuanpeng Yang | Fuqing Zhu | Yaxin Liu | Jizhong Han | Songlin Hu
Proceedings of the 2024 Joint International Conference on Computational Linguistics, Language Resources and Evaluation (LREC-COLING 2024)

Hate speech detection has become an urgent task with the emergence of huge multimodal harmful content (, memes) on social media platforms. Previous studies mainly focus on complex feature extraction and fusion to learn discriminative information from memes. However, these methods ignore two key points: 1) the misalignment of image and text in memes caused by the modality gap, and 2) the uncertainty between modalities caused by the contribution degree of each modality to hate sentiment. To this end, this paper proposes an uncertainty-aware cross-modal alignment (UCA) framework for modeling the misalignment and uncertainty in multimodal hate speech detection. Specifically, we first utilize the cross-modal feature encoder to capture image and text feature representations in memes. Then, a cross-modal alignment module is applied to reduce semantic gaps between modalities by aligning the feature representations. Next, a cross-modal fusion module is designed to learn semantic interactions between modalities to capture cross-modal correlations, providing complementary features for memes. Finally, a cross-modal uncertainty learning module is proposed, which evaluates the divergence between unimodal feature distributions to to balance unimodal and cross-modal fusion features. Extensive experiments on five publicly available datasets show that the proposed UCA produces a competitive performance compared with the existing multimodal hate speech detection methods.


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ESimCSE: Enhanced Sample Building Method for Contrastive Learning of Unsupervised Sentence Embedding
Xing Wu | Chaochen Gao | Liangjun Zang | Jizhong Han | Zhongyuan Wang | Songlin Hu
Proceedings of the 29th International Conference on Computational Linguistics

Contrastive learning has been attracting much attention for learning unsupervised sentence embeddings. The current state-of-the-art unsupervised method is the unsupervised SimCSE (unsup-SimCSE). Unsup-SimCSE takes dropout as a minimal data augmentation method, and passes the same input sentence to a pre-trained Transformer encoder (with dropout turned on) twice to obtain the two corresponding embeddings to build a positive pair. As the length information of a sentence will generally be encoded into the sentence embeddings due to the usage of position embedding in Transformer, each positive pair in unsup-SimCSE actually contains the same length information. And thus unsup-SimCSE trained with these positive pairs is probably biased, which would tend to consider that sentences of the same or similar length are more similar in semantics. Through statistical observations, we find that unsup-SimCSE does have such a problem. To alleviate it, we apply a simple repetition operation to modify the input sentence, and then pass the input sentence and its modified counterpart to the pre-trained Transformer encoder, respectively, to get the positive pair. Additionally, we draw inspiration from the community of computer vision and introduce a momentum contrast, enlarging the number of negative pairs without additional calculations. The proposed two modifications are applied on positive and negative pairs separately, and build a new sentence embedding method, termed Enhanced Unsup-SimCSE (ESimCSE). We evaluate the proposed ESimCSE on several benchmark datasets w.r.t the semantic text similarity (STS) task. Experimental results show that ESimCSE outperforms the state-of-the-art unsup-SimCSE by an average Spearman correlation of 2.02% on BERT-base.

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Smoothed Contrastive Learning for Unsupervised Sentence Embedding
Xing Wu | Chaochen Gao | Yipeng Su | Jizhong Han | Zhongyuan Wang | Songlin Hu
Proceedings of the 29th International Conference on Computational Linguistics

Unsupervised contrastive sentence embedding models, e.g., unsupervised SimCSE, use the InfoNCE loss function in training. Theoretically, we expect to use larger batches to get more adequate comparisons among samples and avoid overfitting. However, increasing batch size leads to performance degradation when it exceeds a threshold, which is probably due to the introduction of false-negative pairs through statistical observation. To alleviate this problem, we introduce a simple smoothing strategy upon the InfoNCE loss function, termed Gaussian Smoothed InfoNCE (GS-InfoNCE). In other words, we add random Gaussian noise as an extension to the negative pairs without increasing the batch size. Through experiments on the semantic text similarity tasks, though simple, the proposed smoothing strategy brings improvements to unsupervised SimCSE.

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RaP: Redundancy-aware Video-language Pre-training for Text-Video Retrieval
Xing Wu | Chaochen Gao | Zijia Lin | Zhongyuan Wang | Jizhong Han | Songlin Hu
Findings of the Association for Computational Linguistics: EMNLP 2022

Video language pre-training methods have mainly adopted sparse sampling techniques to alleviate the temporal redundancy of videos. Though effective, sparse sampling still suffers inter-modal redundancy: visual redundancy and textual redundancy. Compared with highly generalized text, sparsely sampled frames usually contain text-independent portions, called visual redundancy. Sparse sampling is also likely to miss important frames corresponding to some text portions, resulting in textual redundancy. Inter-modal redundancy leads to a mismatch of video and text information, hindering the model from better learning the shared semantics across modalities. To alleviate it, we propose Redundancy-aware Video-language Pre-training. We design a redundancy measurement of video patches and text tokens by calculating the cross-modal minimum dis-similarity. Then, we penalize the high-redundant video patches and text tokens through a proposed redundancy-aware contrastive learning. We evaluate our method on four benchmark datasets, MSRVTT, MSVD, DiDeMo, and LSMDC, achieving a significant improvement over the previous state-of-the-art results.

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InfoCSE: Information-aggregated Contrastive Learning of Sentence Embeddings
Xing Wu | Chaochen Gao | Zijia Lin | Jizhong Han | Zhongyuan Wang | Songlin Hu
Findings of the Association for Computational Linguistics: EMNLP 2022

Contrastive learning has been extensively studied in sentence embedding learning, which assumes that the embeddings of different views of the same sentence are closer. The constraint brought by this assumption is weak, and a good sentence representation should also be able to reconstruct the original sentence fragments. Therefore, this paper proposes an information-aggregated contrastive learning framework for learning unsupervised sentence embeddings, termed InfoCSE.InfoCSE forces the representation of [CLS] positions to aggregate denser sentence information by introducing an additional Masked language model task and a well-designed network. We evaluate the proposed InfoCSE on several benchmark datasets w.r.t the semantic text similarity (STS) task. Experimental results show that InfoCSE outperforms SimCSE by an average Spearman correlation of 2.60% on BERT-base, and 1.77% on BERT-large, achieving state-of-the-art results among unsupervised sentence representation learning methods.


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Early Detection of Fake News by Utilizing the Credibility of News, Publishers, and Users based on Weakly Supervised Learning
Chunyuan Yuan | Qianwen Ma | Wei Zhou | Jizhong Han | Songlin Hu
Proceedings of the 28th International Conference on Computational Linguistics

The dissemination of fake news significantly affects personal reputation and public trust. Recently, fake news detection has attracted tremendous attention, and previous studies mainly focused on finding clues from news content or diffusion path. However, the required features of previous models are often unavailable or insufficient in early detection scenarios, resulting in poor performance. Thus, early fake news detection remains a tough challenge. Intuitively, the news from trusted and authoritative sources or shared by many users with a good reputation is more reliable than other news. Using the credibility of publishers and users as prior weakly supervised information, we can quickly locate fake news in massive news and detect them in the early stages of dissemination. In this paper, we propose a novel structure-aware multi-head attention network (SMAN), which combines the news content, publishing, and reposting relations of publishers and users, to jointly optimize the fake news detection and credibility prediction tasks. In this way, we can explicitly exploit the credibility of publishers and users for early fake news detection. We conducted experiments on three real-world datasets, and the results show that SMAN can detect fake news in 4 hours with an accuracy of over 91%, which is much faster than the state-of-the-art models.


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Multi-hop Selector Network for Multi-turn Response Selection in Retrieval-based Chatbots
Chunyuan Yuan | Wei Zhou | Mingming Li | Shangwen Lv | Fuqing Zhu | Jizhong Han | Songlin Hu
Proceedings of the 2019 Conference on Empirical Methods in Natural Language Processing and the 9th International Joint Conference on Natural Language Processing (EMNLP-IJCNLP)

Multi-turn retrieval-based conversation is an important task for building intelligent dialogue systems. Existing works mainly focus on matching candidate responses with every context utterance on multiple levels of granularity, which ignore the side effect of using excessive context information. Context utterances provide abundant information for extracting more matching features, but it also brings noise signals and unnecessary information. In this paper, we will analyze the side effect of using too many context utterances and propose a multi-hop selector network (MSN) to alleviate the problem. Specifically, MSN firstly utilizes a multi-hop selector to select the relevant utterances as context. Then, the model matches the filtered context with the candidate response and obtains a matching score. Experimental results show that MSN outperforms some state-of-the-art methods on three public multi-turn dialogue datasets.