This paper presents evidence from a large-scale field experiment on conditional cooperation. The study tests how people's pro-social behavior is influenced by social comparisons. The experiment was conducted at the University of Zurich, where students were asked whether they wanted to contribute to two Social Funds. The students were randomly selected and provided with information about the average contribution rate of other students. Half of the students were told that a relatively high percentage (64%) of students contributed, while the other half were told that a relatively low percentage (46%) contributed. The results show that people behave pro-socially, conditional on others. The more others cooperate, the more one is inclined to do so as well. The type of person is important. Some individuals are more influenced by the pro-social behavior of others, while others are not. The study finds that people who contribute to the Funds are more likely to return the sheet with their expectations about others' behavior. The results support the theory of conditional cooperation, showing that people's behavior varies depending on the pro-social behavior of others. The contribution increases if people know that many others contribute as well. However, the effect is limited to certain types of people. The study also finds that people who are more indifferent to others' behavior are more likely to react to the information about others' behavior. The results suggest that people's behavior is influenced by social comparisons, and that people who are more sensitive to others' behavior are more likely to contribute to the Funds. The study concludes that people behave pro-socially conditional on the pro-social behavior of others, and that this behavior is influenced by social comparisons. The results provide evidence for the first time on conditional cooperation outside the laboratory situation.This paper presents evidence from a large-scale field experiment on conditional cooperation. The study tests how people's pro-social behavior is influenced by social comparisons. The experiment was conducted at the University of Zurich, where students were asked whether they wanted to contribute to two Social Funds. The students were randomly selected and provided with information about the average contribution rate of other students. Half of the students were told that a relatively high percentage (64%) of students contributed, while the other half were told that a relatively low percentage (46%) contributed. The results show that people behave pro-socially, conditional on others. The more others cooperate, the more one is inclined to do so as well. The type of person is important. Some individuals are more influenced by the pro-social behavior of others, while others are not. The study finds that people who contribute to the Funds are more likely to return the sheet with their expectations about others' behavior. The results support the theory of conditional cooperation, showing that people's behavior varies depending on the pro-social behavior of others. The contribution increases if people know that many others contribute as well. However, the effect is limited to certain types of people. The study also finds that people who are more indifferent to others' behavior are more likely to react to the information about others' behavior. The results suggest that people's behavior is influenced by social comparisons, and that people who are more sensitive to others' behavior are more likely to contribute to the Funds. The study concludes that people behave pro-socially conditional on the pro-social behavior of others, and that this behavior is influenced by social comparisons. The results provide evidence for the first time on conditional cooperation outside the laboratory situation.