Emphasizing society's expectations enhances charitable giving in NGO advertisements

People are often prompted to donate to charities through subtle cues rather than purely noble intentions. While previous studies have identified various factors that promote prosocial behavior, these factors have not been fully tested in designing effective donation advertisements. Here, focusing on advertisements for the nongovernmental organization WaterAid Japan, we conducted an online nudge experiment (n = 6,232) that revealed emphasizing "society's expectation" is most effective at soliciting donations without adverse psychological effects. We then tested messages with this emphasis in real-world advertisements on a commercial online platform (Yahoo Ads), comparing them to alternative framings that emphasized "inequity aversion," "sense of control," or "warm glow." The "society's expectation" message achieved the highest number of impressions and clicks to the final donation page, suggesting its strong effect in activating prosocial instincts in real-world social decision-making.