Using streaks to promote prosocial behavior within groups

Decades of research and practice show that descriptive social norms (“X% of people are doing it”) are a powerful tool to increase prosocial behavior by conveying its popularity. We introduce a method to encourage norm compliance regardless of popularity: highlighting streaks of behavior across individuals within a group (“the last X people in a row have done it”). In six experiments with over 6,800 participants, we demonstrate that giving people the opportunity to join a small ongoing streak of charitable donors can be a stronger nudge than informing them about a high percentage of past donors, because streaks increase feelings of personal impact on future donors, and signal that the behavior is becoming more prevalent. Encouraging streaks may be an underutilized way to promote prosocial behavior, particularly for actions that are not already popular.