The number of social media platforms (SMP hereinafter) is ever-increasing, and all of these platforms compete for more attention and content. The global social media market is expected to grow to $223.11 billion in 2022 (Social Media Global Market Report, 2022). In an era characterized by the meteoric rise and evolution of Social Media Platforms (SMPs), understanding the interplay between platform features and user behaviors is both critical and complex. In this dissertation, we aim to elucidate the relationship between SMPs and society, with the ultimate objective of fostering a healthier social media ecosystem. This dissertation is comprised of two incisive essays, both of which are underpinned by robust theoretical frameworks. The first essay adopts an expansive purview of the SMP ecosystem. Grounded in Uses and Gratifications Theory and media studies, it establishes a user typology based on the previous typologies and examines the interaction between user motives, SMP scores, and SMP features. Employing the Analytic Hierarchy Process, a sophisticated decision-making tool, the study quantifies utility-driven choices across platforms. A notable revelation is the heterogeneity in user reliance on SMP features, contingent upon their underlying motives. This essay offers critical insights into the multifaceted nature of SMP utilization. The second essay focuses specifically on Reddit's ChangeMyView community, an exemplar of constructive discourse in the SMP environment. It constructs a theoretical model premised on the Elaboration Likelihood Model and the concept of pre-suasion, and utilizes a mixed-methods approach to explore the persuasive strategies using Content Analysis. We also utilize ChatGPT in the Content Analysis to corroborate our inferences. The findings confirm our theorization about the role of the Delta reward system in fostering reflective engagement with content, which leads to informed opinion formation. Collectively, with these essays, we aim to provide extensive insights into the dynamic interplay between SMPs and users. Both essays hold significant implications for research community, SMP decision-makers, organizations that use SMPs, and a broader audience interested in optimizing their social media repertoire. Through a theory-driven and empirical lens, employing several epistemologies, this dissertation provides a holistic depiction of the SMP ecosystem. / Doctor of Philosophy / The landscape of social media is constantly evolving with an ever-growing number of platforms vying for user attention. In this dissertation, we aim to analyze the relationship between social media platforms and their users, seeking ways to foster a healthier and more constructive social media environment. This dissertation is structured into two distinct yet interconnected essays. In the first essay, we look at the broader ecosystem of social media platforms. It categorizes users based on their motivations for using social media, such as seeking information or connecting with others. We examine how different features of social media platforms cater to these diverse motivations. To accomplish this, we employ a method known as the Analytic Hierarchy Process, which is a decision-making tool used to measure and analyze choices. The key insight from this essay is the diversity in how users interact with social media features, and how this interaction is influenced by their underlying motivations. In the second essay, we take a closer look at a specific community on Reddit called ChangeMyView. This community is unique as it encourages users to engage in thoughtful and reasoned debates. In this essay, we develop a theoretical model to understand the mechanisms through which information is processed and opinions are changed within this community with a strong focus on Delta system, a feature that rewards users for successfully changing someone's opinion through challenging their view and pointing the flaws in their thinking. Collectively, the dissertation provides an in-depth understanding of the dynamic relationship between social media platforms and users. It does so through rigorous analysis underpinned by theoretical frameworks. This research is not only academically significant but also has practical implications. It provides valuable insights for decision-makers to improve social media platforms, aids organizations in understanding how best to engage with social media, and informs users on optimizing their social media interactions. In essence, this dissertation serves as a comprehensive analysis that bridges the gap between the ever-evolving features of social media platforms and the multifaceted behaviors of their users.

The paper reports findings from a FAIR principles-based research project dedicated to investigating how cross-field research between the DH and Sociotechnical Sustainable Transport Research could help to enhance the holistic understanding of sociotechnical low-carbon transport transitions.  Using the hashtag search queries #sustainabletransport and #sustainablemobility, 33,121 Tweets (2013-2021) and 8,089 Instagram images including captions (2017/2018-2021) were mined using Python scripts. Quantitative text and sentiment analyses were applied to the Tweets and image captions. Additionally, an automated image analysis using the Instagram dataset was conducted. Synthesized results formed the base for the cross-platform analysis comprising: 1) hot topics, 2) mentioned users, 3) sentiment, 4) co-hashtags. Data were visualized via Tableau, Excel, RAWGraphs, and Bubbl.us. Whereas electromobility, one of Holden et al.’s Grand Narratives for sustainable mobility, has been significantly present in the digital discourse on both platforms (especially Instagram), #sustainabletransport has been closely associated with active transport, especially bicycling, and #sustainablemobility with the electromobility theme. The study has demonstrated the investigative potentials of cross-field cross-platform social media analysis studies and ultimately DH to enhance the understanding of sociotechnical low-carbon transport transitions. Drawing on core results, the paper also suggests an adapted version of the Geelsean Multi-Level Perspective.