Online deliberation platforms have become increasingly important spaces for civic engagement, offering diverse populations the opportunity to participate in public discourse, exchange ideas, and deliberate on policy issues. While these platforms hold great promise for fostering inclusive and participatory dialogue, the quality of contributions often falls short. Users frequently respond in shallow, reactive, or polarized ways. This undermines the deliberative potential of such platforms and raises important questions about how we might design interfaces that actively support more thoughtful and reasoned discourse.

In this dissertation, I examine how reflection can be systematically supported through interface interventions to enhance the deliberative quality of user contributions. Drawing from theories of deliberative democracy, cognitive reflection, and human-computer interaction (HCI), I develop and evaluate novel interface mechanisms that nudge users to reflect more deeply before they contribute to online discussions.

This work focuses on three key dimensions. First, I investigate the impact of reflection timing to encourage deeper thought without impeding conversational flow. Through a series of controlled experiments, I showed that a moderate pause before contribution significantly improves the rationality, coherence, and depth of user arguments. Second, I explore the use of interface-based time nudges to encourage users to pause and reflect. These interventions are designed to be lightweight and non-intrusive, aiming to enhance deliberative engagement while maintaining a positive user experience. Findings from user studies reveal that nudges can improve users’ argument repertoire and reduce impulsive responses. Third, I extend this work to the domain of multimodal reflective nudges, investigating how different modalities can support diverse reflective styles and cognitive preferences. Results show that different modalities produce varied cognitive and emotional effects, suggesting that platform designers should consider modality as a key factor in tailoring reflective support.

Across a series of empirical studies involving over 500 participants, I demonstrate that structured reflection mechanisms, when carefully timed, designed, and personalized, can significantly improve key deliberative indicators. These results not only offer theoretical contributions to the study of deliberation and reflective interaction but also provide practical design insights for civic technologies, public engagement tools, and social computing platforms. Ultimately, this dissertation proposes a design framework for integrating reflection into online deliberation systems, outlining actionable principles for promoting more reasoned, inclusive, and high-quality discourse. By foregrounding reflection as a designable element of digital interaction, my work contributes to the broader conversation on how we can build digital spaces that empower users to think critically, engage constructively, and participate meaningfully in democratic processes.

Shun Yi is a PhD candidate in the Information Systems Technology and Design (ISTD) pillar at the Singapore University of Technology and Design (SUTD), under the supervision of Professor Simon Perrault. Her primary research interest lies in Human-Computer Interaction (HCI), with a focus on designing reflective interfaces, AI-augmented tools, and digital systems that support thoughtful online engagement and collaborative sense-making. Prior to joining the PhD programme, she received her Bachelor’s degree in Quantitative Economics from the Singapore Management University (SMU).