The study looked at why people sometimes put down negative members of their own group. They found that when a group feels very close-knit, negative group members can threaten the group's identity. To protect the group, people may criticize these negative members (known as the black-sheep effect). When groups don't feel as close-knit, this effect is less likely to happen. The researchers tested this by having people rate essays written by group members. They found that when groups felt very unified, people were more likely to criticize negative group members.