The saying “don’t be a toad” in Colombia tells people to mind their own business and not to tell on others. The warning that “snitches get stitches” is common to many societies. It’s easy to imagine why groups adopt prosocial norms like sharing and volunteering. But what sustains an “antisocial” norm like this one? James Robinson talks to Tim Phillips about why people dislike but adopt antisocial norms, what that means for society, and what we can do to change them.