A decision cognizant Kullback-Leibler divergence

In decision making systems involving multiple classifiers there is the need to assess classifier (in)congruence, that is to gauge the degree of agreement between their outputs. A commonly used measure for this purpose is the Kullback–Leibler (KL) divergence. We propose a variant of the KL divergence, named decision cognizant Kullback–Leibler divergence (DC-KL), to reduce the contribution of the minority classes, which obscure the true degree of classifier incongruence. We investigate the properties of the novel divergence measure analytically and by simulation studies. The proposed measure is demonstrated to be more robust to minority class clutter. Its sensitivity to estimation noise is also shown to be considerably lower than that of the classical KL divergence. These properties render the DC-KL divergence a much better statistic for discriminating between classifier congruence and incongruence in pattern recognition systems

Delta Divergence: A Novel Decision Cognizant Measure of Classifier Incongruence

In pattern recognition, disagreement between two classifiers regarding the predicted class membership of an observation can be indicative of an anomaly and its nuance. Since, in general, classifiers base their decisions on class a posteriori probabilities, the most natural approach to detecting classifier incongruence is to use divergence. However, existing divergences are not particularly suitable to gauge classifier incongruence. In this paper, we postulate the properties that a divergence measure should satisfy and propose a novel divergence measure, referred to as delta divergence. In contrast to existing measures, it focuses on the dominant (most probable) hypotheses and, thus, reduces the effect of the probability mass distributed over the non dominant hypotheses (clutter). The proposed measure satisfies other important properties, such as symmetry, and independence of classifier confidence. The relationship of the proposed divergence to some baseline measures, and its superiority, is shown experimentally

Unlocking the Pragmatics of Emoji: Evaluation of the Integration of Pragmatic Markers for Sarcasm Detection

Emojis have become an integral element of online communications, serving as a powerful, under-utilised resource for enhancing pragmatic understanding in NLP. Previous works have highlighted their potential for improvement of more complex tasks such as the identification of figurative literary devices including sarcasm due to their role in conveying tone within text. However present state-of-the-art does not include the consideration of emoji or adequately address sarcastic markers such as sentiment incongruence. This work aims to integrate these concepts to generate more robust solutions for sarcasm detection leveraging enhanced pragmatic features from both emoji and text tokens. This was achieved by establishing methodologies for sentiment feature extraction from emojis and a depth statistical evaluation of the features which characterise sarcastic text on Twitter. Current convention for generation of training data which implements weak-labelling using hashtags or keywords was evaluated against a human-annotated baseline; postulated validity concerns were verified where statistical evaluation found the content features deviated significantly from the baseline, highlighting potential validity concerns for many prominent works on the topic to date. Organic labelled sarcastic tweets containing emojis were crowd sourced by means of a survey to ensure valid outcomes for the sarcasm detection model. Given an established importance of both semantic and sentiment information, a novel sentiment-aware attention mechanism was constructed to enhance pattern recognition, balancing core features of sarcastic text: sentiment incongruence and context. This work establishes a framework for emoji feature extraction; a key roadblock cited in literature for their use in NLP tasks. The proposed sarcasm detection pipeline successfully facilitates the task using a GRU neural network with sentiment-aware attention, at an accuracy of 73% and promising indications regarding model robustness as part of a framework which is easily scalable for the inclusion of any future emojis released. Both enhanced sentiment information to supplement context in addition to consideration of the emoji were found to improve outcomes for the task

The functional neurophysiological sequelae associated with high frequency dream recallers

Background: Dreaming is a universal experience, yet there is considerable inter-individual variability with regard to dream recall frequency (DRF). Research on DRF has been prolific leading to the development of various models delineating possible processes involved in dream recall. One such model is the 'arousal-retrieval' model positing that intra-sleep wakefulness is required for dream traces to be encoded into long-term storage, essentially proposing increased DRF as a product of a better memory for dreams. Results from recent studies support this model by demonstrating longer periods of intra-sleep wakefulness in high frequency recallers (HFRs) compared to low frequency recallers (LFRs). Furthermore, results showed heightened brain reactivity, as well as increased regional cerebral blood flow in areas in the brain associated with dream production. These results are indicative of the existence of a functional neurophysiological trait innate to HRs, while also supporting the premise that apart from a better memory for dreams, HRs also may produce more dreams. Awakenings from rapid eye movement (REM) sleep yield the highest dream recall rates, rendering REM sleep as a reasonable starting point for studying rates of dream production. Furthermore, increased dream production during REM sleep might also affect related processes, for example, leading to enhanced overnight emotional memory consolidation and emotion regulation. Hypotheses: The current study investigated the functional neurophysiological sequelae associated with HFRs in a design where HFRs are compared to LFRs. Hypotheses include: (1) HFRs will score significantly higher on certain personality dimensions; (2) HFRs will experience significantly more awakenings, as well as longer periods of intra-sleep wakefulness; (3) HFRs will have significantly higher rates of dream production as measured by the frequency of eye movements (REM density) during REM sleep; and (4) increased dream production during REM sleep will lead to enhanced overnight emotional memory consolidation and emotion regulation in HFRs. Methods: The study consisted of two groups of healthy young adults: high frequency recallers (n = 19) and low frequency recallers (n = 17) who underwent polysomnographic recordings on two non-consecutive nights. Memory tasks and affective questionnaires were completed before and after a night of sleep. Results: (1) HFRs scored significantly higher on the 'agreeableness' personality dimension and on the Boundary Questionnaire; (2) HFRs experienced significantly more awakenings, especially from stage 2 non-rem (NREM) sleep, as well as significantly longer periods of intra-sleep wakefulness; (3) no significant between-group differences with regard to REM density, nor (4) overnight emotional memory consolidation and emotion regulation were found. Conclusion: Results support, firstly, the proposition that certain personality traits, differences in sleep architecture, and increased DRF are an expression of a functional neurophysiological arrangement innate to HFRs. Secondly, the findings suggest that NREM sleep, as opposed to REM sleep, is important in relation to DRF in this specific population. This is the first study to not only replicate existing findings, but to also contribute to the extant literature by illuminating additional characteristics and features associated with HFRs

Distributed Scaffolding: Wiki Collaboration Among Latino High School Chemistry Students

The primary purpose of this study was to evaluate if wiki collaboration among Latino high school chemistry students can help reduce the science achievement gap between Latino and White students. The study was a quasi-experimental pre/post control group mixed-methods design. It used three intact sections of a high school chemistry course. The first research question asked if there is a difference in academic achievement between a treatment and control group on selected concepts from the topics of bonding, physical changes, and chemical changes, when Latino high school chemistry students collaborate on a quasi-natural wiki project. Overall results for all three activities (Bonding, Physical Changes, and Chemical Changes) indicated no significant difference between the wiki and control group. However, students performing the chemical changes activity did significantly better than their respective control group. Furthermore, there was a significant association, with large effect size, between group membership and ability to overcome the misconception that aqueous ionic reactants in precipitation reactions exist as molecular pairs of ions. Qualitative analysis of classroom and computer lab dialogue, discussion board communication, student focus groups, teacher interviews, and wiki content attributes the better performance of the chemical changes wiki group to favorable differences in intersubjectivity and calibrated assistance, as well as learning about submicroscopic representations of precipitation reactions in multiple contexts. Furthermore, the nonsignificant result overall points to an aversion to peer editing as a possible cause. Drawing considerably on Vygotsky and Piaget, the results are discussed within the context of how distributed scaffolding facilitated medium levels of cognitive conflict. The second research question asked what the characteristics of distributed metacognitive scaffolding are when Latino high school chemistry students collaborate on a quasi-natural wiki project. Results suggested a higher frequency of metacognitive scaffolding by the teacher, over peers, for content knowledge and making connections knowledge. Teacher metacognitive scaffolding often took the form of posting discussion board questions designed to stimulate student reflection on their content or creativity. On the other hand, both teacher and peer metacognitive scaffolding for general goals knowledge and strategy knowledge was relatively infrequent. Recommendations are offered for improving teacher and peer metacognitive scaffolding

The effects of multiple forms of disgust exposure on the processing of emotional photographic images

Exposure to disgust has been found to influence both short term attentional processes and decision making. This thesis proposed to investigate the extent to which disgust exposure can also influence emotion processing and evaluation – specifically of real world photographic images. To this end, both behavioural and event related potential (ERP) paradigms were utilised. Disgust was induced in multiple ways – through videos, written scenarios and briefly presented prime images. After exposure to disgusting prime images, participants high in disgust propensity were quicker to respond to disgust targets (a congruence effect that was not obtained for fear targets preceded by fear primes). After reading disgusting sentences, participants who were high in disgust propensity were more likely to judge pleasant food images (as well as disgusting images) as unpleasant (but not other pleasant images) thus reconfirming the relationship between disgust and digestion. ERP data revealed that individuals high in attentional shifting ability had a suppressed Late Positive Potential (LPP) to both disgusting and threatening images but that this effect was washed out through reading disgusting scenarios. After exposure to disgusting videos, attentional focus was associated with an increased LPP response to disgust (but not fear) images. There was a strong occipital LPP enhancement for disgust (over both fear and neutral) that was independent of disgust exposure and could represent an electrophysiological marker of disgust processing. The results demonstrate that both the processing of disgusting images, as well as the processing of emotional images of a variety of content (both positive and negative), can be affected by disgust exposure. These effects can be seen early in processing and also influence later emotional assessments, and are strongly dependent on individual differences in disgust propensity and attentional control. The results highlight the extent to which disgust can influence multiple short-term emotion processing mechanisms

Investigating Phantom Motor Execution as treatment of Phantom Limb Pain

Phantom Limb Pain (PLP) is commonly suffered by people with amputations and even though it has been studied for centuries, it remains a mysterious object of debate among researchers. For one thing, despite the vast number of proposed PLP treatments, no therapy has so far proved to be reliably effective. For another, studies attempting to provide a mechanistic explanation of the condition have produced mixed and inconsistent results, thus providing unreliable guidance for devising new treatment approaches. Phantom Motor Execution (PME) – exertion of voluntary phantom limb movements – aims at restoring control over the phantom limb and the exercise of such control has been hypothesized to reverse neural changes implicated in PLP. Preliminary evidence supporting this hypothesis has been provided by clinical investigations on upper limb amputees. The main purpose of this doctoral thesis was to provide high quality and unbiased evidence for the use of PME as a treatment of PLP, by probing its efficacy with a Randomized Controlled Trial (RCT) on both upper and lower limb amputees. However, the implementation of this clinical investigation required of additional technology development related the extraction of motor volition via Myoelectric Pattern Recognition (MPR). In practice, this doctoral work consisted in the extension of PME technology to lower limb amputations by proposing and validating a new and more user-friendly recording method to acquire myoelectric signals. The use of PME was then shown to be efficacious in relieving PLP even in the lower limb population with a case study.Another necessity for providing unbiased evidence was to ensure that the highest standards were met when designing, conducting, analysing and reporting the results of the RCT. For this reason, the protocol for the RCT and the prospective Statistical Analysis Plan (SAP) were designed and published. The RCT was established as an international, multi-center effort in 2017 and it is expected to reach its conclusion in September 2021. Preliminary results of the RCT regarding the primary outcome showed reduction of PLP above what is considered clinically relevant, and whereas a higher reduction was obtained with PME, this was not statistically significant over the control treatment. The available evidence at this stage indicates that the RCT will not be able to rule out the role of contextual factors other than PME in providing pain relief. Having at hand a way to alleviate PLP provided a unique opportunity to investigate and identify its neural correlates, therefore this became a secondary aim of this thesis. In particular, patients suffering from PLP were followed regarding their pain trajectory through the therapy and brain imaging studies with functional Magnetic Resonance Imaging (fMRI) and electroencephalography (EEG) were performed. The present doctoral thesis reports part of this work by showing the early results of a cross-sectional study on the EEG correlates of PLP. The results show that it is possible to use machine-learning techniques to discriminate EEG recorded from patients with and without PLP. The findings further point to this technique as a promising target for future longitudinal research aiming at elucidating the neural mechanisms underlying PLP

Pancreatic cancer : prevention through improved diagnostics in individuals at risk

With the intent of timely detecting malignant precursors or pancreatic cancer (PC) in an early stage, current guidelines recommend surveillance for patients with pancreatic cystic neoplasms (PCNs), such as intraductal papillary mucinous neoplasms (IPMN), and individuals at risk (IAR) for familiar/hereditary pancreatic cancer (PC). This surveillance is mainly performed with magnetic resonance imaging (MRI). However, despite the associated examination time and costs, MRI is still suboptimal regarding its accuracy in predicting malignancy. This thesis aims to contribute towards improved secondary prevention of PC through more efficient and accurate diagnostic methods in patients with IPMN and familiar/hereditary PC through (i) a shorter MRI protocol, (ii) new imaging features and radiomics models for the prediction of malignancy, (iii) a better understanding of the surveillance program for IAR. In Study I, we compared a short (SP) and a comprehensive pancreatic MRI protocol (CP), with an acquisition time of approximately 8 and 35 minutes, respectively, in a cohort of 154 patients with PCNs. Our results showed that the SP provided equivalent clinical information in evaluating mural nodules, as well as cystic and main pancreatic duct diameters, compared to the more time-consuming and expensive CP in the surveillance of PCNs. In Study II, we assessed whether two novel features, such as volumetry and elongation value (EV) and other routinely used resection criteria, could predict malignancy in a cohort of 106 patients operated for BD- and mixed-type IPMN. Cases with mass-forming PC were excluded as a possible cause of main pancreatic duct (MPD) dilatation. Our results showed that volumetry and EV were not predictive for malignancy. Only elevated serum levels of CA19-9, mural nodules and dilated MPD (in the absence of stricturing masses) were associated with malignancy. In Study III, we evaluated the performance of MRI-based radiomics models in the preoperative prediction of malignancy in 130 patients operated for BD and mixed-type IPMN after exclusion of mass-forming PC. The radiomics models were internally cross-validated. Our results showed that a “pure” radiomics model outperformed a model including standard clinical and imaging features, suggesting that it might effectively predict malignancy in BD-IPMN even without standard clinical/imaging information. In Study IV, we described the imaging findings and the performance of a mainly MRI-based surveillance program in a cohort of 278 individuals at risk (IAR) for familial/hereditary PC. Our results showed that focal pancreatic lesions were identified in over half of IAR, the vast majority being small cysts. No lesions with high-grade dysplasia were detected. Five patients had PC, with the same prevalence of stage I and stage IV. The sensitivity and positive predictive values for detecting PC and its precursors were low (60% and 37%, respectively). In conclusion, a short pancreatic MRI protocol can be safely used in the surveillance of PCNs without losing relevant clinical information. Although novel imaging features cannot predict malignancy in IPMN, radiomics have shown its potentiality. In the context of individuals at risk for familial or hereditary PC undergoing surveillance, the early diagnosis of PC is still challenging with “traditional” cross-imaging methods such as MRI

Exploring the emergence and disappearance of transableism on transabled.org: Digital ethnography of a transient mental illness

Transableism is an historical condition that originated in an online community named transabled.org, existing between 1996 and 2013. Transableism manifested as the desire to be disabled, arising out of a felt sense of incongruence between one’s inner sense of identity as disabled, and one’s bodily reality as abled. During its existence, transableism attracted clinical attention and was proposed for entry into the Diagnostic and Statistical Manual of Mental Disorders (DSM) under the descriptor Body Integrity Identity Disorder (BIID). However, despite its growing visibility, in 2012 BIID failed to enter the DSM and the online transabled community disappeared. The aim of this thesis is to explore transableism’s rapid emergence and subsequent failure to achieve formal medical recognition. The key questions underpinning this thesis are (1) why did transableism emerge and (2) why did it disappear? Taking a qualitative approach, this thesis uses digital ethnography to analyse all content posted to transabled.org in its active years. The originality of this thesis lies in the way it uses the theoretical lens of an ecological niche of ‘transient mental illness’ (Hacking, 1998) to examine the historical, cultural and social factors which informed transableism, opening up a new, never before explored perspective. Use of the ecological niche of transient mental illness model provides a nuanced and holistic answer to the questions which underpin this thesis. I argue that transableism emerged because it reflected and expressed broader cultural understandings and tensions surrounding authentic versus inauthentic disability. Its emergence was also facilitated by a centralised model of community leadership which, for a time, successfully fostered a coherent group identity and enlisted the interests of clinicians. On the other hand, transableism disappeared because BIID failed to conform to an accepted authenticity politics of disabled identity and was policed accordingly. In addition, although the centralised model of community leadership initially facilitated transableism, towards the later years, this model collapsed, leading to conflict, community attrition and moderator burn out. Overall, this thesis makes 6 original contributions to knowledge by advancing understandings within (1) extant transableism scholarship, (2) broader medical sociological literatures, (3) the disability studies literature, (4) scholarship that explores claims to authentic identities, and the limits of such claims, (5) the literature on leadership and moderation practices within online communities and (6) the health advocacy community literature