Norms are people's beliefs about what others commonly do or value, and they can encourage individuals to change their behaviors to act in accordance with these perceptions. For example, if people believe others are buying all-electric vehicles (EVs), it should encourage them to purchase an EV for their next automobile. However, norms do not always change people's behaviors, and this project examines the factors determining what leads norms to be more contagious. In particular, it considers the role of dynamic norms, which are beliefs about how people's behaviors or beliefs are changing across time. These trend perceptions (e.g., an increasing number of people are purchasing EV automobiles) may be especially important in responding to major societal challenges. The project examines what qualities of trends lead people to follow suit when they see others as changing (leading the trend to grow) versus what attributes of a trend lead it to fail to spread and merely fade away. For example, attributes such as seeing a trend as likely to be long-lived (rather than a fad) or as being part of a broader shared social cause should encourage people to conform to that trend.<br/><br/>This project investigates important society trends affecting public health, sustainability, energy security, and social inequality by considering four attributes about trends that make them more likely to inspire people to adopt them: Longevity (will this trend last?), Universality (will this trend spread widely?), Common Cause (are people changing for a cause?), and Sufficiency (is more change needed for that cause?). Understanding how these conditions lead people to join social movements helps explain when trends spread or fade, improving the understanding of when society is more likely to change in response to societal challenges. The research uses correlational, experimental, and field work approaches with nonprofit partnerships. The findings can inform organizations and policy makers in promoting practices that increase energy independence and reduce societal discord.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.