Regulatory-focus based nudges to sustain citizen science reporting: results from a two-year randomized trial

Citizen science projects are playing an increasingly prominent role in addressing global health and environmental challenges, yet they often struggle to sustain volunteer engagement over time. This study evaluates the use of nudging intervention grounded in regulatory focus theory to enhance participation in a large-scale invasive mosquito-monitoring initiative. In a two-year randomized controlled trial (N = 600), participants received in-app notifications framed in either eager, vigilant, or neutral terms. We analyzed temporal and individual-level shifts in reporting behavior using paired-sample t-tests and generalized linear mixed-effects models. Results showed that regulatory focus based nudges significantly increased the likelihood of daily reporting relative to neutral controls. Importantly, prevention-focused individuals benefited most when message framing aligned with their dispositional regulatory orientation, evidencing a regulatory fit effect. Nudging not only counteracted the typical seasonal decline in engagement but also showed sustained effects post-intervention. These findings underscore the relevance of theory-informed interventions that can sustainably strengthen involvement at scale, offering a widely applicable solution to one of the field’s most persistent challenges. By strategically emphasizing either aspirational gains or precautionary responsibilities, organizers can reduce attrition and enhance data quality in citizen science initiatives.