Keep the cat in the bag: Children understand that telling a friend's secret can harm the friendship.

Secrets play a powerful role in human social relationships. Here, we examine the developmental trajectory of 3- to 10-year-old children's (N = 630) expectations about (a) how relationships impact whether people will keep secrets, and (b) how relationships are impacted when a confidee keeps versus tells a confider's secret. Sophisticated expectations about the role of secrets in relationship maintenance develop across childhood. In particular, school-age children (6- to 10-year-olds) expect friends to be more likely to keep each other's secrets than nonfriends (Study 1), and expect that if a friend breaks this norm and shares his friend's secret with a third-party, it will harm the friendship (Studies 2 and 3). These expectations were specific to inferences about secrets: school-age children did not expect that sharing (or keeping) a friend's fact or surprise would impact the friendship strength (Studies 2 and 3). These findings did not hold for preschoolers (3- to 5-year-olds), who did not have clear expectations linking secret sharing to friendship strength. Taken together, our results indicate that by 6 years of age, children understand that social relationships can increase people's obligations to keep each other's secrets, and that failing to do so can harm the relationship. (PsycInfo Database Record (c) 2020 APA, all rights reserved).