(Dis)engagement by design How digital design choices impact smartphone overuse and digital well-being

As engagement-driven design features increasingly shape everyday smartphone and social media environments, concerns have grown that such design contributes to perceived overuse and undermines digital well-being. At the same time, both smartphones and social media apps offer built-in tools and settings intended to help users manage their use. Individuals may thus seek to regulate their use through technology-based disconnection strategies, referring to tools and settings within the technology itself that support users in limiting or structuring their engagement, such as notification management, app limits, and screen time tracking.
Despite growing scholarly and societal interest, little systematic evidence exists regarding whether people who perceive overuse actually turn to such strategies, whether these strategies are effective, and how specific design features shape both established and emerging habits. This dissertation addresses these gaps across four empirical chapters. The first chapter provides longitudinal insights by investigating how perceived smartphone overuse relates to self-initiated technology-based disconnection strategies in the general population. Building on this, the subsequent three chapters employ controlled field experiments to examine how notifications and algorithmic personalization affect digital well-being, objective use, and habits.
Across these studies, three overarching conclusions emerge. Perceived overuse is widespread, but does not consistently translate into intentions or actions to reduce use. Technology-based disconnection is common, yet often ineffective, and when effective it tends to compromise key benefits such as enjoyment. Finally, while design features like personalization play a powerful role in sustaining established habits, early habit formation appears less sensitive to such features. Together, these findings underscore that improving digital well-being cannot rely on user initiative alone, but requires structural, evidence-based changes to platform design.