Check or reject? Trust and motivation development in app-based warning systems

App-based warning systems notify people of upcoming hazards, but they will only be used if users trust them, which, in turn, depends on the system’s performance (i.e., number of false alarms). Thus, the present work aims to present initial evidence on how trust in warning systems develops over time. We conducted two field experiments in which participants used a mobile (fire) emergency warning system for two weeks with variable conditions. Study 1 combined online and in-app questionnaires in a longitudinal design (Nscreening = 623, Napp = 265). Notably, false alarms led to a significant decrease in trustworthiness, trust, motivation, and intention to use, whereas a responsibility diffusion manipulation did not have negative effects. In study 2, we examined under real-life conditions app users’ on-site responses after false alarms by applying questionnaires, behavioural observations, and in-depth interviews (Nscreening = 119, Napp = 58). Before the field experiment on site, participants completed a fire safety training. While the training had a positive influence on motivation, gamification of the app showed no effects. Overall, the results agree with recent models about the development of trust over time and highlight the dynamic nature of our relationship to warning systems. Finally, we derive implications for warning system design.