A Human-centric Approach to NLP in Healthcare Applications

The abundance of personal health information available to healthcare professionals can be a facilitator to better care. However, it can also be a barrier, as the relevant information is often buried in the sheer amount of personal data, and healthcare professionals already lack time to take care of both patients and their data. This dissertation focuses on the role of natural language processing (NLP) in healthcare and how it can surface information relevant to healthcare professionals by modeling the extensive collections of documents that describe those whom they serve. In this dissertation, the extensive natural language data about a person is modeled as a set of documents, where the model inference is at the level of the individual, but evidence supporting that inference is found in a subset of their documents. The effectiveness of this modeling approach is demonstrated in the context of three healthcare applications. In the first application, clinical coding, document-level attention is used to model the hierarchy between a clinical encounter and its documents, jointly learning the encounter labels and the assignment of credits to specific documents. The second application, suicidality assessment using social media, further investigates how document-level attention can surface "high-signal" posts from the document set representing a potentially at-risk individual. Finally, the third application aims to help healthcare professionals write discharge summaries using an extract-then-abstract multidocument summarization pipeline to surface relevant information. As in many healthcare applications, these three applications seek to assist, not replace, clinicians. Evaluation and model design thus centers around healthcare professionals' needs. In clinical coding, document-level attention is shown to align well with professional clinical coders' expectations of evidence. In suicidality assessment, document-level attention leads to better and more time-efficient assessment by surfacing document-level evidence, shown empirically using a theoretically grounded time-aware evaluation measure and a dataset annotated by suicidality experts. Finally, extract-then-abstract summarization pipelines that assist healthcare professionals in writing discharge summaries are evaluated by their ability to surface faithful and relevant evidence

Nowcasting user behaviour with social media and smart devices on a longitudinal basis: from macro- to micro-level modelling

The adoption of social media and smart devices by millions of users worldwide over the last decade has resulted in an unprecedented opportunity for NLP and social sciences. Users publish their thoughts and opinions on everyday issues through social media platforms, while they record their digital traces through their smart devices. Mining these rich resources offers new opportunities in sensing real-world events and indices (e.g., political preference, mental health indices) in a longitudinal fashion, either at the macro (population)-, or at the micro(user)-level. The current project aims at developing approaches to “nowcast" (predict the current state of) such indices at both levels of granularity. First, we build natural language resources for the static tasks of sentiment analysis, emotion disclosure and sarcasm detection over user-generated content. These are important for opinion monitoring on a large scale. Second, we propose a general approach that leverages textual data derived from generic social media streams to nowcast political indices at the macro-level. Third, we leverage temporally sensitive and asynchronous information to nowcast the political stance of social media users, at the micro-level using multiple kernel learning. We then focus further on the micro-level modelling, to account for heterogeneous data sources, such as information derived from users' smart phones, SMS and social media messages, to nowcast time-varying mental health indices of a small cohort of users on a longitudinal basis. Finally, we present the challenges faced when applying such micro-level approaches in a real-world setting and propose directions for future research

Deep learning with knowledge graphs for fine-grained emotion classification in text

This PhD thesis investigates two key challenges in the area of fine-grained emotion detection in textual data. More specifically, this work focuses on (i) the accurate classification of emotion in tweets and (ii) improving the learning of representations from knowledge graphs using graph convolutional neural networks.The first part of this work outlines the task of emotion keyword detection in tweets and introduces a new resource called the EEK dataset. Tweets have previously been categorised as short sequences or sentence-level sentiment analysis, and it could be argued that this should no longer be the case, especially since Twitter increased its allowed character limit. Recurrent Neural Networks have become a well-established method to classify tweets over recent years, but have struggled with accurately classifying longer sequences due to the vanishing and exploding gradient descent problem. A common technique to overcome this problem has been to prune tweets to a shorter sequence length. However, this also meant that often potentially important emotion carrying information, which is often found towards the end of a tweet, was lost (e.g., emojis and hashtags). As such, tweets mostly face also problems with classifying long sequences, similar to other natural language processing tasks. To overcome these challenges, a multi-scale hierarchical recurrent neural network is proposed and benchmarked against other existing methods. The proposed learning model outperforms existing methods on the same task by up to 10.52%. Another key component for the accurate classification of tweets has been the use of language models, where more recent techniques such as BERT and ELMO have achieved great success in a range of different tasks. However, in Sentiment Analysis, a key challenge has always been to use language models that do not only take advantage of the context a word is used in but also the sentiment it carries. Therefore the second part of this work looks at improving representation learning for emotion classification by introducing both linguistic and emotion knowledge to language models. A new linguistically inspired knowledge graph called RELATE is introduced. Then a new language model is trained on a Graph Convolutional Neural Network and compared against several other existing language models, where it is found that the proposed embedding representations achieve competitive results to other LMs, whilst requiring less pre-training time and data. Finally, it is investigated how the proposed methods can be applied to document-level classification tasks. More specifically, this work focuses on the accurate classification of suicide notes and analyses whether sentiment and linguistic features are important for accurate classification

When a few words are not enough: improving text classification through contextual information

Traditional text classification approaches may be ineffective when applied to texts with insufficient or limited number of words due to brevity of text and sparsity of feature space. The lack of contextual information can make texts ambiguous; hence, text classification approaches relying solely on words may not properly capture the critical features of a real-world problem. One of the popular approaches to overcoming this problem is to enrich texts with additional domain-specific features. Thus, this thesis shows how it can be done in two realworld problems in which text information alone is insufficient for classification. While one problem is depression detection based on the automatic analysis of clinical interviews, another problem is detecting fake online news. Depression profoundly affects how people behave, perceive, and interact. Language reveals our ideas, moods, feelings, beliefs, behaviours and personalities. However, because of inherent variations in the speech system, no single cue is sufficiently discriminative as a sign of depression on its own. This means that language alone may not be adequate for understanding a person’s mental characteristics and states. Therefore, adding contextual information can properly represent the critical features of texts. Speech includes both linguistic content (what people say) and acoustic aspects (how words are said), which provide important clues about the speaker’s emotional, physiological and mental characteristics. Therefore, we study the possibility of effectively detecting depression using unobtrusive and inexpensive technologies based on the automatic analysis of language (what you say) and speech (how you say it). For fake news detection, people seem to use their cognitive abilities to hide information, which induces behavioural change, thereby changing their writing style and word choices. Therefore, the spread of false claims has polluted the web. However, the claims are relatively short and include limited content. Thus, capturing only text features of the claims will not provide sufficient information to detect deceptive claims. Evidence articles can help support the factual claim by representing the central content of the claim more authentically. Therefore, we propose an automated credibility assessment approach based on linguistic analysis of the claim and its evidence articles

Proceedings of the Seventh Italian Conference on Computational Linguistics CLiC-it 2020

On behalf of the Program Committee, a very warm welcome to the Seventh Italian Conference on Computational Linguistics (CLiC-it 2020). This edition of the conference is held in Bologna and organised by the University of Bologna. The CLiC-it conference series is an initiative of the Italian Association for Computational Linguistics (AILC) which, after six years of activity, has clearly established itself as the premier national forum for research and development in the fields of Computational Linguistics and Natural Language Processing, where leading researchers and practitioners from academia and industry meet to share their research results, experiences, and challenges

Conversation analysis for computational modelling of task-oriented dialogue

Current methods of dialogue modelling for Conversational AI (CAI) bear little resemblance to the manner in which humans organise conversational interactions. The way utterances are represented, interpreted, and generated are determined by the necessities of the chosen technique and do not resemble those used during natural conversation. In this research we propose a new method of representing task-oriented dialogue, for the purpose of computational modelling, which draws inspiration from the study of human conversational structures, Conversation Analysis (CA). Our approach unifies two well established, yet disparate, methods of dialogue representation: Dialogue Acts (DA), which provide valuable semantic and intentional information, and the Adjacency Pair (AP), which are the predominant method by which structure is defined within CA. This computationally compatible approach subsequently benefits from the strengths, whilst overcoming the weaknesses, of its components.To evaluate this thesis we first develop and evaluate a novel CA Modelling Schema (CAMS), which combines concepts of DA’s and AP’s to form AP-type labels. Thus creating a single annotation scheme that is able to capture the semantic and syntactic structure of dialogue. We additionally annotate a task-oriented corpus with our schema to create CAMS-KVRET, a first-of-its-kind DA and AP labelled dataset. Next, we conduct detailed investigations of input representation and architectural considerations in order to develop and refine several ML models capable of automatically labelling dialogue with CAMS labels. Finally, we evaluate our proposed method of dialogue representation, and accompanying models, against several dialogue modelling tasks, including next label prediction, response generation, and structure representation.With our evaluation of CAMS we show that it is both reproducible, and inherently learnable, even for novice annotators. And further, that it is most intuitively applied to task-oriented dialogues. During development of our ML classifiers we determined that, in most cases, input and architectural choices are equally applicable to DA and AP classification. We evaluated our classification models against CAMS-KVRET, and achieved high test set classification accuracy for all label components of the corpus. Additionally, we were able to show that, not only is our model capable of learning the semantic and structural aspects of both the DA and AP components, but also that AP are more predictive of future utterance labels, and thus representative of the overall dialogue structure. These finding were further supported by the results of our next-label prediction and response generation experiments. Moreover, we found AP were able to reduce the perplexity of the generative model. Finally, by using χ2 analysis to create dialogue structure graphs, we demonstrate that AP produce a more generalised and efficient method of dialogue representation. Thus, our research has shown that integrating DA with AP, into AP-type labels, captures the semantic and syntactic structure of an interaction, in a format that is independent of the domain or topic, and which benefits the computational modelling of task-oriented dialogues