Unsupervised Dialogue Act Induction using Gaussian Mixtures

This paper introduces a new unsupervised approach for dialogue act induction. Given the sequence of dialogue utterances, the task is to assign them the labels representing their function in the dialogue. Utterances are represented as real-valued vectors encoding their meaning. We model the dialogue as Hidden Markov model with emission probabilities estimated by Gaussian mixtures. We use Gibbs sampling for posterior inference. We present the results on the standard Switchboard-DAMSL corpus. Our algorithm achieves promising results compared with strong supervised baselines and outperforms other unsupervised algorithms.Comment: Accepted to EACL 201

Composing Deep Learning and Bayesian Nonparametric Methods

Recent progress in Bayesian methods largely focus on non-conjugate models featured with extensive use of black-box functions: continuous functions implemented with neural networks. Using deep neural networks, Bayesian models can reasonably fit big data while at the same time capturing model uncertainty. This thesis targets at a more challenging problem: how do we model general random objects, including discrete ones, using random functions? Our conclusion is: many (discrete) random objects are in nature a composition of Poisson processes and random functions}. Thus, all discreteness is handled through the Poisson process while random functions captures the rest complexities of the object. Thus the title: composing deep learning and Bayesian nonparametric methods. This conclusion is not a conjecture. In spacial cases such as latent feature models , we can prove this claim by working on infinite dimensional spaces, and that is how Bayesian nonparametric kicks in. Moreover, we will assume some regularity assumptions on random objects such as exchangeability. Then the representations will show up magically using representation theorems. We will see this two times throughout this thesis. One may ask: when a random object is too simple, such as a non-negative random vector in the case of latent feature models, how can we exploit exchangeability? The answer is to aggregate infinite random objects and map them altogether onto an infinite dimensional space. And then assume exchangeability on the infinite dimensional space. We demonstrate two examples of latent feature models by (1) concatenating them as an infinite sequence (Section 2,3) and (2) stacking them as a 2d array (Section 4). Besides, we will see that Bayesian nonparametric methods are useful to model discrete patterns in time series data. We will showcase two examples: (1) using variance Gamma processes to model change points (Section 5), and (2) using Chinese restaurant processes to model speech with switching speakers (Section 6). We also aware that the inference problem can be non-trivial in popular Bayesian nonparametric models. In Section 7, we find a novel solution of online inference for the popular HDP-HMM model

Domain Adaptation for Statistical Classifiers

The most basic assumption used in statistical learning theory is that training data and test data are drawn from the same underlying distribution. Unfortunately, in many applications, the "in-domain" test data is drawn from a distribution that is related, but not identical, to the "out-of-domain" distribution of the training data. We consider the common case in which labeled out-of-domain data is plentiful, but labeled in-domain data is scarce. We introduce a statistical formulation of this problem in terms of a simple mixture model and present an instantiation of this framework to maximum entropy classifiers and their linear chain counterparts. We present efficient inference algorithms for this special case based on the technique of conditional expectation maximization. Our experimental results show that our approach leads to improved performance on three real world tasks on four different data sets from the natural language processing domain

Guided Probabilistic Topic Models for Agenda-setting and Framing

Probabilistic topic models are powerful methods to uncover hidden thematic structures in text by projecting each document into a low dimensional space spanned by a set of topics. Given observed text data, topic models infer these hidden structures and use them for data summarization, exploratory analysis, and predictions, which have been applied to a broad range of disciplines. Politics and political conflicts are often captured in text. Traditional approaches to analyze text in political science and other related fields often require close reading and manual labeling, which is labor-intensive and hinders the use of large-scale collections of text. Recent work, both in computer science and political science, has used automated content analysis methods, especially topic models to substantially reduce the cost of analyzing text at large scale. In this thesis, we follow this approach and develop a series of new probabilistic topic models, guided by additional information associated with the text, to discover and analyze agenda-setting (i.e., what topics people talk about) and framing (i.e., how people talk about those topics), a central research problem in political science, communication, public policy and other related fields. We first focus on study agendas and agenda control behavior in political debates and other conversations. The model we introduce, Speaker Identity for Topic Segmentation (SITS), is able to discover what topics that are talked about during the debates, when these topics change, and a speaker-specific measure of agenda control. To make the analysis process more effective, we build Argviz, an interactive visualization which leverages SITS's outputs to allow users to quickly grasp the conversational topic dynamics, discover when the topic changes and by whom, and interactively visualize the conversation's details on demand. We then analyze policy agendas in a more general setting of political text. We present the Label to Hierarchy (L2H) model to learn a hierarchy of topics from multi-labeled data, in which each document is tagged with multiple labels. The model captures the dependencies among labels using an interpretable tree-structured hierarchy, which helps provide insights about the political attentions that policymakers focus on, and how these policy issues relate to each other. We then go beyond just agenda-setting and expand our focus to framing--the study of how agenda issues are talked about, which can be viewed as second-level agenda-setting. To capture this hierarchical views of agendas and frames, we introduce the Supervised Hierarchical Latent Dirichlet Allocation (SHLDA) model, which jointly captures a collection of documents, each is associated with a continuous response variable such as the ideological position of the document's author on a liberal-conservative spectrum. In the topic hierarchy discovered by SHLDA, higher-level nodes map to more general agenda issues while lower-level nodes map to issue-specific frames. Although qualitative analysis shows that the topic hierarchies learned by SHLDA indeed capture the hierarchical view of agenda-setting and framing motivating the work, interpreting the discovered hierarchy still incurs moderately high cost due to the complex and abstract nature of framing. Motivated by improving the hierarchy, we introduce Hierarchical Ideal Point Topic Model (HIPTM) which jointly models a collection of votes (e.g., congressional roll call votes) and both the text associated with the voters (e.g., members of Congress) and the items (e.g., congressional bills). Customized specifically for capturing the two-level view of agendas and frames, HIPTM learns a two-level hierarchy of topics, in which first-level nodes map to an interpretable policy issue and second-level nodes map to issue-specific frames. In addition, instead of using pre-computed response variable, HIPTM also jointly estimates the ideological positions of voters on multiple interpretable dimensions

Automatic Emotion Recognition: Quantifying Dynamics and Structure in Human Behavior.

Emotion is a central part of human interaction, one that has a huge influence on its overall tone and outcome. Today's human-centered interactive technology can greatly benefit from automatic emotion recognition, as the extracted affective information can be used to measure, transmit, and respond to user needs. However, developing such systems is challenging due to the complexity of emotional expressions and their dynamics in terms of the inherent multimodality between audio and visual expressions, as well as the mixed factors of modulation that arise when a person speaks. To overcome these challenges, this thesis presents data-driven approaches that can quantify the underlying dynamics in audio-visual affective behavior. The first set of studies lay the foundation and central motivation of this thesis. We discover that it is crucial to model complex non-linear interactions between audio and visual emotion expressions, and that dynamic emotion patterns can be used in emotion recognition. Next, the understanding of the complex characteristics of emotion from the first set of studies leads us to examine multiple sources of modulation in audio-visual affective behavior. Specifically, we focus on how speech modulates facial displays of emotion. We develop a framework that uses speech signals which alter the temporal dynamics of individual facial regions to temporally segment and classify facial displays of emotion. Finally, we present methods to discover regions of emotionally salient events in a given audio-visual data. We demonstrate that different modalities, such as the upper face, lower face, and speech, express emotion with different timings and time scales, varying for each emotion type. We further extend this idea into another aspect of human behavior: human action events in videos. We show how transition patterns between events can be used for automatically segmenting and classifying action events. Our experimental results on audio-visual datasets show that the proposed systems not only improve performance, but also provide descriptions of how affective behaviors change over time. We conclude this dissertation with the future directions that will innovate three main research topics: machine adaptation for personalized technology, human-human interaction assistant systems, and human-centered multimedia content analysis.PhDElectrical Engineering: SystemsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/133459/1/yelinkim_1.pd