Common knowledge that help is needed increases helping behavior in children.

Although there is considerable evidence that at least some helping behavior is motivated by genuine concern for others' well-being, sometimes we also help solely out of a sense of obligation to the persons in need. Our sense of obligation to help may be particularly strong when there is common knowledge between the helper and the helpee that the helpee needs help. To test whether children's helping behavior is affected by having common knowledge with the recipient about the recipient's need, 6-year-olds faced a dilemma: They could either collect stickers or help an experimenter. Children were more likely to help when they and the experimenter had common knowledge about the experimenter's plight (because they heard it together) than when they each had private knowledge about it (because they heard it individually). These results suggest that already in young children common knowledge can heighten the sense of obligation to help others in need.