From Exposure to Action: How Digital Campaign Ads Mobilize Citizens to Protect the Amazon

Despite widespread use of digital campaigns, it remains unclear which message features most effectively mobilize citizens and through which psychological pathways. In collaboration with a global NGO, we evaluate a COP 2025 climate campaign using a large-scale, cross-national email field experiment targeting 200,000 recipients, alongside an online survey experiment in Brazil, the UK, and the US with representative citizen samples. Both studies manipulate type of message appeal, framing, and tone, while holding images and calls-to-action constant. The primary outcome is whether citizens draft political messages to policymakers, with the survey experiment also measuring attitudes and intended behavior. The field experiment tests these effects in a real-world context and uses LLM-guided textual analysis to examine which persuasive appeals citizens naturally write. The survey experiment complements this by measuring mediators such as social norms, perceived urgency and issue-specific or general efficacy. Pre- and post-treatment measures assess shifts in attitudes, intended behavior, and the psychological pathways driving change. Together, the studies illuminate how citizens engage with policymakers, shedding light on the mechanisms linking communication strategies to political representation and participatory democracy.