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Trustworthy Multimodal Fusion for Robust Sentiment Analysis with Ordinal Constraints

Core Concepts
A trustworthy multimodal sentiment analysis model that dynamically estimates uncertainty distributions for each modality and fuses them using Bayesian fusion to obtain a more robust multimodal representation. An ordinal regression loss is introduced to constrain the multimodal distributions to follow the ordinal relationships of sentiment categories.
The paper proposes a trustworthy multimodal sentiment analysis model called TMSON that addresses the limitations of previous multimodal fusion methods. The key highlights are: Unimodal Feature Representation: Separate unimodal feature extractors are designed for text, visual, and audio modalities. Multitask learning is explored to capture both modality-specific and modality-shared features. Uncertainty Distribution Estimation: An uncertainty distribution estimation module is introduced to dynamically estimate the uncertainty distribution for each modality. The mean of the distribution represents the modal intensity, and the variance represents the uncertainty. Multimodal Distribution Fusion: A multimodal distribution fusion module is proposed to fuse the unimodal distributions using Bayesian fusion. The fused multimodal distribution has a smaller variance and more robust performance compared to individual modalities. Ordinal Sentiment Regression: An ordinal regression loss is introduced to constrain the fused multimodal distributions to follow the ordinal relationships of sentiment categories. This helps the model better capture the inherent ordinal structure of sentiment labels. Extensive experiments on three benchmark datasets (CMU-MOSI, CMU-MOSEI, and SIMS) demonstrate that TMSON outperforms state-of-the-art multimodal sentiment analysis models. The model also exhibits superior robustness to noise disturbance.
The average length of video clips in the CMU-MOSI dataset is 4.2 seconds. The CMU-MOSEI dataset contains 23,453 utterances, with 16,265 in the training set, 2,545 in the validation set, and 4,643 in the test set. The SIMS dataset contains 2,281 video clips with an average of 15 words per clip.
"Previous multimodal methods are based on deterministic embeddings, representing samples as deterministic points in the embedding space, thereby ignoring data uncertainty." "Our fusion method is order-invariant, that is, it does not depend on the fusion order of modalities." "Ordinal regression aims to learn a mapping function: X → Y, where X is the data space and Y = {C1, C2, . . . , Ck} is the target space containing k categories. These label categories are in an ordering relationship: C1 ≺ C2 ≺ · · · ≺ Ck, where ≺ is an ordinal relation reflecting the relative position of the labels."

Deeper Inquiries

How can the proposed TMSON framework be extended to handle missing modalities during inference

In the context of the proposed TMSON framework, handling missing modalities during inference can be crucial for maintaining the robustness and reliability of the sentiment analysis system. One approach to extend TMSON to address missing modalities is through a mechanism called modality dropout. Modality dropout involves randomly masking out one or more modalities during inference to simulate the absence of certain modalities. This allows the model to adapt and make predictions based on the available modalities, similar to how dropout is used in neural networks to improve generalization. During inference, when a modality is missing, the uncertainty estimation module can provide insights into the reliability of the available modalities. By considering the uncertainty scores of the observed modalities, the fusion module can dynamically adjust the weighting of modalities to compensate for the missing information. This adaptive fusion mechanism ensures that the model can still make informed predictions even in the absence of certain modalities. Additionally, incorporating a mechanism for modality imputation can also be beneficial. This involves leveraging the information from the available modalities to predict the missing modality data. Techniques such as data imputation using statistical methods or leveraging correlations between modalities can help fill in the gaps caused by missing modalities. By integrating modality dropout and imputation strategies, the TMSON framework can enhance its robustness and performance in handling missing modalities during inference.

What are the potential applications of the trustworthy multimodal fusion approach beyond sentiment analysis, such as in other multimodal tasks like emotion recognition or video understanding

The trustworthy multimodal fusion approach proposed in TMSON for sentiment analysis can have various applications beyond sentiment analysis in tasks that involve multimodal data integration. Some potential applications include: Emotion Recognition: The TMSON framework can be applied to emotion recognition tasks where multiple modalities such as facial expressions, speech, and physiological signals are used to infer emotional states. By estimating uncertainty and fusing multimodal information in a reliable manner, TMSON can improve the accuracy and robustness of emotion recognition systems. Video Understanding: In the context of video understanding, where videos contain diverse modalities like audio, visual, and text, TMSON can be utilized to analyze and interpret the content of videos. By integrating information from different modalities while considering their reliability, TMSON can enhance video understanding tasks such as action recognition, scene understanding, and event detection. Healthcare: In healthcare applications, where multimodal data from patient records, images, and sensor data are used for diagnosis and monitoring, TMSON can play a vital role. By fusing information from various modalities while accounting for uncertainty, TMSON can assist in tasks like disease diagnosis, patient monitoring, and personalized treatment recommendations. Human-Computer Interaction: In human-computer interaction scenarios, where user inputs come in various forms like text, speech, and gestures, TMSON can improve the understanding of user intentions and sentiments. By integrating and analyzing multimodal data reliably, TMSON can enhance applications such as virtual assistants, sentiment analysis in customer feedback, and interactive systems. By applying the principles of trustworthy multimodal fusion beyond sentiment analysis, TMSON can contribute to a wide range of multimodal tasks that require robust and reliable integration of diverse data sources.

How can the ordinal regression loss be further improved to better capture the nuanced relationships between sentiment categories

To enhance the ordinal regression loss in capturing nuanced relationships between sentiment categories, several strategies can be employed: Fine-grained Ordinal Labels: Utilizing a finer granularity in the ordinal labels can provide more detailed information about the sentiment categories. Instead of discrete categories, a continuous scale or finer intervals can be used to represent the sentiment intensity. This allows the model to learn more subtle distinctions between different sentiment levels. Dynamic Margin Adjustment: Introducing a dynamic margin in the ordinal loss function that adapts during training based on the difficulty of the samples can improve the model's ability to capture nuanced relationships. By adjusting the margin based on the similarity between samples, the model can focus on learning the intricate differences between sentiment categories. Triplet Selection Strategies: Implementing more sophisticated triplet selection strategies can help in constructing informative training samples for ordinal regression. Strategies like hard negative mining, where challenging samples are prioritized, or curriculum learning, where the difficulty of triplets is gradually increased, can enhance the model's ability to learn the ordinal relationships effectively. Regularization Techniques: Incorporating regularization techniques such as L1 or L2 regularization on the ordinal regression parameters can prevent overfitting and encourage the model to generalize better to unseen data. Regularization helps in controlling the complexity of the model and improving its ability to capture subtle nuances in the sentiment categories. By incorporating these strategies, the ordinal regression loss in TMSON can be further refined to better capture the nuanced relationships between sentiment categories and improve the overall performance of the sentiment analysis system.