Calls to action and user engagement: The role of visual and verbal requests in nonprofit advocacy on Facebook

A common strategy to boost user engagement on social media is to incorporate requests into posts. While previous research has focused on the effects of direct verbal requests (i.e., commands), the role of subtler, indirect verbal and visual requests remains underexplored. We address this gap through a quantitative content analysis of 2250 Facebook posts from the 100 largest U.S. nonprofit organizations. Using a social semiotics lens, we argue that both verbal and visual modes can convey requests, although each relies on distinct semiotic resources. The influence of requests on user engagement may thus be shaped by general semiotic principles applicable to both modes as well as modality-specific principles. In line with our assumptions, users prefer posts that clearly reveal a charity's persuasive intent through verbal and visual requests (general principle of clarity). Moreover, posts fostering clarity by exclusively featuring either direct or indirect verbal requests are associated with greater user engagement compared to those combining both types. However, users are more responsive to indirect than direct verbal requests (verbal principle of nuance) and tend to be distracted from the verbal text when posts include a direct gaze image (visual principle of captivation).