Preheating Prosocial Behaviour

Casey Wichman
About This Project

Assistant Professor Casey Wichman's paper "Preheating Prosocial Behaviour" was published in The Economic Journal. Wichman writes:

One prevailing theory in economics is that people donate to public goods because they receive a "warm glow" from donating. In this paper, we gather social media data for more than 20,000 Twitter users before and after donating to a public good. We analyze the sentiment of their tweets and find that Twitter users' moods increase before donating. This finding contradicts previous evidence and suggests that people may engage in prosocial behavior because they are in a good mood rather than the other way around. These findings could be valuable for charitable organizations designing fundraising campaigns, especially on social media platforms.


We provide new evidence on motivations for voluntary contributions to public goods in a natural setting. Using natural-language processing on users’ Twitter posts, we measure revealed sentiment changes before and after making a donation to Wikipedia. We find strong evidence that sentiment improves in the hour and minutes directly before contributing, which we call ‘preheating.’ Results are robust to alternative fixed effects and approaches to inference, and supported by a complementary online experiment with randomised mood inducement among Twitter users. Preheating suggests that affective states influence giving, in addition to reward-seeking, utility-maximising behaviour that has been documented in other contexts.

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