Protesting can take many forms—from waving signs, lighting candles, and making speeches to holding sit-ins, writing letters, and filing lawsuits. Some unusual tactics—such as paying for a purchase in pennies to slow down business—aren’t used often, but once successful, they can spread like wildfire.

Sarah Soule, a professor of organizational behavior at the Stanford Graduate School of Business, wanted to see just how such protest tactics have spread among social-movement organizations. To do that, she and Stanford sociology graduate student Dan Wang used network analysis to examine collaborations among groups.

For the study, Soule and Wang started with a publicly available database containing more than 24,000 protest events documented by The New York Times between 1960 and 1995. Soule and her collaborators developed the database over a decade with funding from the National Science Foundation, and it now is a useful staple for the study of protest in the United States for that period, she says.

The newspaper accounts often reported who organized and sponsored the protests. If two or more groups were listed, the researchers considered those groups as having collaborated. They then tracked each organization’s unique repertoire of tactics and asked, “Do they ever use those again in an event where they are protesting alone?” Soule says. The researchers found that groups being at a protest together did indeed influence diffusion of those tactics from one group to the next.

This idea has been discussed before, Soule says, but no one had rigorously applied a method to control for the known biases in doing this kind of network analysis. “Is it really that these organizations learned from each other, and the tactic diffused? Or is it just that these organizations are sort of similar, and so they do the same sorts of things?” Soule says. The method they developed was able to disentangle those effects.

From their analysis, Soule and Wang found that organizations with a broader repertoire of protest tactics tended to adopt new tactics more readily. More collaboration also facilitated the transfer of tactics. Groups that had more initial overlap in their tactical repertoires also experienced more diffusion.

Soule says organizational learning theory is often applied to the for-profit sector but not to the nonprofit sector, into which social movement organizations tend to fall. “One thing those types of organizations can think about is how collaboration does lead to learning and therefore to innovation,” she says.

The researchers “really put these network methods to extraordinarily good use in coming up with original findings about tactical diffusion,” says David Meyer, a professor of sociology and political science at the University of California, Irvine. “I think it’s going to inspire lots of other people to follow on what they’re doing.”

Dan J. Wang and Sarah A. Soule, “Social Movement Organizational Collaboration: Networks of Learning and the Diffusion of Protest Tactics, 1960–1995,” American Journal of Sociology 117, 2012.

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