That is, only passersby who actually talked to the ex-perimenters could be included in the experiment. Thus, one mightargue that only participants with a certain prosocial orientationtook part in the experiments, which might have influenced theirprosocial response (i.e., acting as a chaperone for a group ofjuvenile delinquents on a 2-hr trip to the zoo). However, as
people who actually talked to the experimenters could have been more social than other which could lead to them saying yes to the smaller request more.