The study tested how different incentives affect people's charitable giving over time. They did this by having over 700 participants make repeated decisions about donating to charity in two rounds. The researchers found that when participants did a good deed before deciding to donate, they actually gave less. However, those who were encouraged to donate through social comparisons were more likely to give to charity again compared to those who were given money as a reward. This shows that how we are encouraged to be generous can impact our future giving behavior.