Doctor of Philosophy (Ph.D.)

Permanent URI for this collectionhttp://192.248.9.226/handle/123/12348

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Measuring trustworthiness of workers in the crowdsourced collection of subjective judgements
(2023) Meedin, GSN; Perera, GIUS
Social media platforms have become integral parts of our lives, enabling people to connect, share, and express themselves on a global scale. Alongside the benefits, there are also substantial challenges that arise from the unfiltered and unrestricted nature of these platforms. One such challenge is the presence of inappropriate and hateful content on social media. While platforms employ algorithms and human moderators to identify and remove inappropriate content, they often struggle to keep up with the constant flood of new posts. Social media posts are written in a variety of languages and multimedia formats. As a result, social media platforms find it more difficult to filter these before reaching a more diverse audience range, as moderation of these social media platform posts necessitates greater contextual, social, and cultural insights, as well as language skills. Social media platforms use a variety of techniques to capture these insights, and linguistic expertise to effectively moderate social media posts. These techniques help platforms better understand the degrees of content and ensure that inappropriate or harmful posts are accurately identified and addressed. These techniques include Natural Language Processing (NLP) algorithms, keyword and phrase detection, image and video recognition, contextual analysis, cultural sensitivity training, machine learning, AI improvement etc. Data annotation forms the foundation for training these algorithms and identifying and classifying various types of content accurately. Often crowdsourcing platforms such as Mechanical Turk and Crowd Flower are used to get the datasets annotated in these techniques. The accuracy of the annotation process is crucial for effective content moderation on social media platforms. Crowdsourcing platforms take several trust measures to maintain the quality of annotations and to minimize errors. In addition to these procedures, determining the trustworthiness of workers on crowdsourcing platforms is critical for ensuring the quality and reliability of the contributions they give. Accuracy metrics, majority voting, completion rate, inter-rater agreement, and reputation scores are a few such measurements used by existing researchers. Even though majority voting is used to ensure consensus, existing research shows that the annotated results do not reflect the actual user perception and hence the trustworthiness of the annotation is less. In this research, a crowdsourcing platform was designed and developed to allow the annotation process by overcoming the limitations of measuring trustworthiness which would facilitate identifying inappropriate social media content using crowd responses. Here the research focus was limited to social media content written in Sinhala and Sinhala words written in English (Singlish) letters as the most popular Mechanical Turk and Crowd Flower do not allow workers from Sri Lanka. As outcomes of this research, a few novel approaches were proposed, implemented, and evaluated for hate speech annotation, hate speech corpus generation, measuring user experience, identifying worker types and personality traits and hate speech post-identification. In addition, the implemented crowdsourcing platform can extend the task designs to other annotation tasks; language and inappropriate content identification, text identification from images, hate speech propagator ranking and sentiment analysis. When evaluating the quality of the results for accuracy and performance, it was identified that the consensus-based approach of ensuring the trustworthiness of crowdsourcing participants is highly affected by the crowd’s biases and the Hawthorne effect. Therefore, a comparison and analysis of the annotation quality of the crowdsourcing platform with consensus, reputation, and gold v standard-based approaches were conducted and a model to measure the trustworthiness of crowd response was developed. The major outcome of this research is the crowdsourcing platform that can be used for local annotation processes with the assurance of worker reliability. The number of tasks completed by the workers within a given period, the number of tasks attempted by each worker within a given period, the percentage of tasks completed compared to tasks attempted, time taken to complete tasks, the accuracy of responses considering golden rules, time taken to submit responses after each task assignment and the consistency of response time provided were identified as the quantitative measurements to assess the trustworthiness of workers. After this identification, the relationship between reputation score, performance score and bias score was formulated by analysing the worker responses. The worker behaviour model and trust measurement model showed an accuracy of 87% and 91% respectively after comparing with the expert response score which can be further improved by incorporating contextual analysis, worker belief and opinion analysis. The proposed methodology would accelerate data collection, enhance data quality, and would promote the development of high-quality labelled datasets. Keywords: Annotation, Collaboration, Crowdsourcing, Human-Computer Interaction, Trustworthiness

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