Modality to Modality Translation: An Adversarial Representation Learning and Graph Fusion Network for Multimodal Fusion

Learning joint embedding space for various modalities is of vital importance for multimodal fusion. Mainstream modality fusion approaches fail to achieve this goal, leaving a modality gap which heavily affects cross-modal fusion. In this paper, we propose a novel adversarial encoder-decoder-classifier framework to learn a modality-invariant embedding space. Since the distributions of various modalities vary in nature, to reduce the modality gap, we translate the distributions of source modalities into that of target modality via their respective encoders using adversarial training. Furthermore, we exert additional constraints on embedding space by introducing reconstruction loss and classification loss. Then we fuse the encoded representations using hierarchical graph neural network which explicitly explores unimodal, bimodal and trimodal interactions in multi-stage. Our method achieves state-of-the-art performance on multiple datasets. Visualization of the learned embeddings suggests that the joint embedding space learned by our method is discriminative. code is available at: \url{https://github.com/TmacMai/ARGF_multimodal_fusion}Comment: Accepted by AAAI-2020; code is available at: https://github.com/TmacMai/ARGF_multimodal_fusio

Towards uncertainty-aware and label-efficient machine learning of human expressive behaviour

The ability to recognise emotional expressions from non-verbal behaviour plays a key role in human-human interaction. Endowing machines with the same ability is critical to enriching human-computer interaction. Despite receiving widespread attention so far, human-level automatic recognition of affective expressions is still an elusive task for machines. Towards improving the current state of machine learning methods applied to affect recognition, this thesis identifies two challenges: label ambiguity and label scarcity. Firstly, this thesis notes that it is difficult to establish a clear one-to-one mapping between inputs (face images or speech segments) and their target emotion labels, considering that emotion perception is inherently subjective. As a result, the problem of label ambiguity naturally arises in the manual annotations of affect. Ignoring this fundamental problem, most existing affect recognition methods implicitly assume a one-to-one input-target mapping and use deterministic function learning. In contrast, this thesis proposes to learn non-deterministic functions based on uncertainty-aware probabilistic models, as they can naturally accommodate the one-to-many input-target mapping. Besides improving the affect recognition performance, the proposed uncertainty-aware models in this thesis demonstrate three important applications: adaptive multimodal affect fusion, human-in-the-loop learning of affect, and improved performance on downstream behavioural analysis tasks like personality traits estimation. Secondly, this thesis aims to address the challenge of scarcity of affect labelled datasets, caused by the cumbersome and time-consuming nature of the affect annotation process. To this end, this thesis notes that audio and visual feature encoders used in the existing models are label-inefficient i.e. learning them requires large amounts of labelled training data. As a solution, this thesis proposes to pre-train the feature encoders using unlabelled data to make them more label-efficient i.e. using as few labelled training examples as possible to achieve good emotion recognition performance. A novel self-supervised pre-training method is proposed in this thesis by posing hand-engineered emotion features as task-specific representation learning priors. By leveraging large amounts of unlabelled audiovisual data, the proposed self-supervised pre-training method demonstrates much better label efficiency compared to the commonly employed pre-training methods

Towards uncertainty-aware and label-efficient machine learning of human expressive behaviour

The ability to recognise emotional expressions from non-verbal behaviour plays a key role in human-human interaction. Endowing machines with the same ability is critical to enriching human-computer interaction. Despite receiving widespread attention so far, human-level automatic recognition of affective expressions is still an elusive task for machines. Towards improving the current state of machine learning methods applied to affect recognition, this thesis identifies two challenges: label ambiguity and label scarcity. Firstly, this thesis notes that it is difficult to establish a clear one-to-one mapping between inputs (face images or speech segments) and their target emotion labels, considering that emotion perception is inherently subjective. As a result, the problem of label ambiguity naturally arises in the manual annotations of affect. Ignoring this fundamental problem, most existing affect recognition methods implicitly assume a one-to-one input-target mapping and use deterministic function learning. In contrast, this thesis proposes to learn non-deterministic functions based on uncertainty-aware probabilistic models, as they can naturally accommodate the one-to-many input-target mapping. Besides improving the affect recognition performance, the proposed uncertainty-aware models in this thesis demonstrate three important applications: adaptive multimodal affect fusion, human-in-the-loop learning of affect, and improved performance on downstream behavioural analysis tasks like personality traits estimation. Secondly, this thesis aims to address the challenge of scarcity of affect labelled datasets, caused by the cumbersome and time-consuming nature of the affect annotation process. To this end, this thesis notes that audio and visual feature encoders used in the existing models are label-inefficient i.e. learning them requires large amounts of labelled training data. As a solution, this thesis proposes to pre-train the feature encoders using unlabelled data to make them more label-efficient i.e. using as few labelled training examples as possible to achieve good emotion recognition performance. A novel self-supervised pre-training method is proposed in this thesis by posing hand-engineered emotion features as task-specific representation learning priors. By leveraging large amounts of unlabelled audiovisual data, the proposed self-supervised pre-training method demonstrates much better label efficiency compared to the commonly employed pre-training methods

Quantum Cognitively Motivated Context-Aware Multimodal Representation Learning for Human Language Analysis

A long-standing goal in the field of Artificial Intelligence (AI) is to develop systems that can perceive and understand human multimodal language. This requires both the consideration of context in the form of surrounding utterances in a conversation, i.e., context modelling, as well as the impact of different modalities (e.g., linguistic, visual acoustic), i.e., multimodal fusion. In the last few years, significant strides have been made towards the interpretation of human language due to simultaneous advancement in deep learning, data gathering and computing infrastructure. AI models have been investigated to either model interactions across distinct modalities, i.e., linguistic, visual and acoustic, or model interactions across parties in a conversation, achieving unprecedented levels of performance. However, AI models are often designed with only performance as their design target, leaving aside other essential factors such as transparency, interpretability, and how humans understand and reason about cognitive states. In line with this observation, in this dissertation, we develop quantum probabilistic neural models and techniques that allow us to capture rational and irrational cognitive biases, without requiring a priori understanding and identification of them. First, we present a comprehensive empirical comparison of state-of-the-art (SOTA) modality fusion strategies for video sentiment analysis. The findings provide us helpful insights into the development of more effective modality fusion models incorporating quantum-inspired components. Second, we introduce an end-to-end complex-valued neural model for video sentiment analysis, simulating quantum procedural steps, outside of physics, into the neural network modelling paradigm. Third, we investigate non-classical correlations across different modalities. In particular, we describe a methodology to model interactions between image and text for an information retrieval scenario. The results provide us with theoretical and empirical insights to develop a transparent end-to-end probabilistic neural model for video emotion detection in conversations, capturing non-classical correlations across distinct modalities. Fourth, we introduce a theoretical framework to model user's cognitive states underlying their multimodal decision perspectives, and propose a methodology to capture interference of modalities in decision making. Overall, we show that our models advance the SOTA on various affective analysis tasks, achieve high transparency due to the mapping to quantum physics meanings, and improve post-hoc interpretability, unearthing useful and explainable knowledge about cross-modal interactions

Multimodal Visual Sensing: Automated Estimation of Engagement

Viele moderne Anwendungen der künstlichen Intelligenz beinhalten bis zu einem gewissen Grad ein Verständnis der menschlichen Aufmerksamkeit, Aktivität, Absicht und Kompetenz aus multimodalen visuellen Daten. Nonverbale Verhaltenshinweise, die mit Hilfe von Computer Vision und Methoden des maschinellen Lernens erkannt werden, enthalten wertvolle Informationen zum Verständnis menschlicher Verhaltensweisen, einschließlich Aufmerksamkeit und Engagement. Der Einsatz solcher automatisierten Methoden im Bildungsbereich birgt ein enormes Potenzial. Zu den nützlichen Anwendungen gehören Analysen im Klassenzimmer zur Messung der Unterrichtsqualität und die Entwicklung von Interventionen zur Verbesserung des Unterrichts auf der Grundlage dieser Analysen sowie die Analyse von Präsentationen, um Studenten zu helfen, ihre Botschaften überzeugend und effektiv zu vermitteln. Diese Dissertation stellt ein allgemeines Framework vor, das auf multimodaler visueller Erfassung basiert, um Engagement und verwandte Aufgaben anhand visueller Modalitäten zu analysieren. Während sich der Großteil der Engagement-Literatur im Bereich des affektiven und sozialen Computings auf computerbasiertes Lernen und auf Lernspiele konzentriert, untersuchen wir die automatisierte Engagement-Schätzung im Klassenzimmer unter Verwendung verschiedener nonverbaler Verhaltenshinweise und entwickeln Methoden zur Extraktion von Aufmerksamkeits- und emotionalen Merkmalen. Darüber hinaus validieren wir die Effizienz der vorgeschlagenen Ansätze an realen Daten, die aus videografierten Klassen an Universitäten und weiterführenden Schulen gesammelt wurden. Zusätzlich zu den Lernaktivitäten führen wir eine Verhaltensanalyse von Studenten durch, die kurze wissenschaftliche Präsentationen unter Verwendung von multimodalen Hinweisen, einschließlich Gesichts-, Körper- und Stimmmerkmalen, halten. Neben dem Engagement und der Präsentationskompetenz nähern wir uns dem Verständnis des menschlichen Verhaltens aus einer breiteren Perspektive, indem wir die Analyse der gemeinsamen Aufmerksamkeit in einer Gruppe von Menschen, die Wahrnehmung von Lehrern mit Hilfe von egozentrischer Kameraperspektive und mobilen Eyetrackern sowie die automatisierte Anonymisierung von audiovisuellen Daten in Studien im Klassenzimmer untersuchen. Educational Analytics bieten wertvolle Möglichkeiten zur Verbesserung von Lernen und Lehren. Die Arbeit in dieser Dissertation schlägt einen rechnerischen Rahmen zur Einschätzung des Engagements und der Präsentationskompetenz von Schülern vor, zusammen mit unterstützenden Computer-Vision-Problemen.Many modern applications of artificial intelligence involve, to some extent, an understanding of human attention, activity, intention, and competence from multimodal visual data. Nonverbal behavioral cues detected using computer vision and machine learning methods include valuable information for understanding human behaviors, including attention and engagement. The use of such automated methods in educational settings has a tremendous potential for good. Beneficial uses include classroom analytics to measure teaching quality and the development of interventions to improve teaching based on these analytics, as well as presentation analysis to help students deliver their messages persuasively and effectively. This dissertation presents a general framework based on multimodal visual sensing to analyze engagement and related tasks from visual modalities. While the majority of engagement literature in affective and social computing focuses on computer-based learning and educational games, we investigate automated engagement estimation in the classroom using different nonverbal behavioral cues and developed methods to extract attentional and emotional features. Furthermore, we validate the efficiency of proposed approaches on real-world data collected from videotaped classes at university and secondary school. In addition to learning activities, we perform behavior analysis on students giving short scientific presentations using multimodal cues, including face, body, and voice features. Besides engagement and presentation competence, we approach human behavior understanding from a broader perspective by studying the analysis of joint attention in a group of people, teachers' perception using egocentric camera view and mobile eye trackers, and automated anonymization of audiovisual data in classroom studies. Educational analytics present valuable opportunities to improve learning and teaching. The work in this dissertation suggests a computational framework for estimating student engagement and presentation competence, together with supportive computer vision problems