From Awareness to Action: Ambient Display and Customizable Attention Signals for Self-regulated Smartphone Usage

People often use their phones longer than optimal. Researchers have developed various tools to reduce screen time, primarily using blocking or self-tracking and reflection strategies. However, blocking does not support the internalization of motivation, and self-tracking and reflection often lack constant exposure to tracking data. We propose ambient display, an always-on feedback mechanism, to convey self-tracking data and support reflection as a novel intervention for problematic smartphone usage. We report on the design and evaluation of TIMER, an Android app that displays the current session length and offers customizable attention signals to enhance the ambient display's noticeability when needed. Participants (N = 41) used TIMER for three weeks: no intervention in Week 1, ambient display in Week 2, and ambient display with attention signals in Week 3. We found that the ambient display reduced daily screen time by 38 minutes (10.7% of the baseline), and adding attention signals led to a further reduction of 32 minutes (9.0%). Participants reported improved competence in controlling smartphone usage, but their motivation did not change. While TIMER's simplicity and effectiveness in raising awareness were well received, we explore ways to further enhance ambient displays and better support users' motivation.