The latest thinking on social networks explains why new technologies and innovative behaviors really spread. It’s not about “going viral.”

When Twitter launched in March 2006, the earth did not move. Its founders and a few early funders were excited about the technology, but the microblogging site was not the immediate blockbuster you might imagine it was, given that it now has more than 300 million users and has become a wildly influential marketing tool for businesses, nonprofits, and even politicians. Rather, Twitter crept along in its early months, growing slowly.

So, what happened to transform it from another also-ran into one of the largest communication platforms in the world?

Twitter seems on the surface to be the kind of technology that journalist Malcolm Gladwell and Wharton School marketing professor Jonah Berger refer to as “contagious.”1 To jump-start Twitter’s growth, its founders decided to promote it at a South by Southwest (SXSW) Interactive conference in 2007, where it was a big hit. From there, people assume it rapidly spread across the United States through the internet, thanks to social contacts connected by what network researchers call “weak ties” and “long bridges.”2 Two years later, in 2009, Twitter adoptions were catapulted into a global orbit when a major opinion leader, Oprah Winfrey, sent her first tweet on her talk show.

That narrative is easy to grasp and compelling. It gives startups, and the people who invest in them, a road map for success. Unfortunately, it is also inaccurate, and the road map leads to a dead end.

In a very interesting study, Twitter’s actual growth pattern was revealed to be surprisingly geographic.3 Friends and neighbors adopted the technology from one another in much the same way people join a PTA fund-raiser or get excited about a candidate for town office. Twitter didn’t spread virally across the internet; it spread locally, like a grassroots social movement.

Although that explanation of Twitter’s success is less sensational than the usual “going viral” story, it is far more useful for understanding how social networks promote behavioral change. And it corresponds with a growing body of research that describes behavioral change as a complex contagion, which needs reinforcing ties and wide bridges to spread. We’ll explore those concepts here. They are key elements in a diffusion playbook for companies attempting to launch innovations and facilitate both customer and employee adoption.


1. M. Gladwell, “The Tipping Point: How Little Things Can Make a Big Difference” (Boston: Little, Brown, 2000); and J. Berger, “Contagious: Why Things Catch On” (New York: Simon & Schuster, 2013).

2. M. Granovetter, “The Strength of Weak Ties,” American Journal of Sociology 78, no. 6 (May 1973): 1,360-1,380.

3. J.L. Toole, M. Cha, and M.C. González, “Modeling the Adoption of Innovations in the Presence of Geographic and Media Influences,” PLoS ONE 7, no. 1 (Jan. 19, 2012).

4. D. Centola and M. Macy, “Complex Contagions and the Weakness of Long Ties,” American Journal of Sociology 113, no. 3 (November 2007): 702-734.

5. D. Centola, “The Spread of Behavior in an Online Social Network Experiment,” Science (Sept. 3, 2010): 1,194-1,997.

6. Granovetter, “The Strength of Weak Ties.”

7. Ibid.

8. Gladwell, “The Tipping Point.”

9. D. Centola, “The Social Origins of Networks and Diffusion,” American Journal of Sociology 120, no. 5 (March 2015): 1,295-1,338.

10. M.T. Hansen, “The Search-Transfer Problem: The Role of Weak Ties in Sharing Knowledge Across Organization Subunits,” Administrative Science Quarterly 44, no. 1 (March 1999): 82-111; and D. Centola and A. Baronchelli, “The Spontaneous Emergence of Conventions: An Experimental Study of Cultural Evolution,” Proceedings of the National Academy of Sciences 112, no. 7 (Feb. 2, 2015): 1,989-1,994.

11. J. Ugander, L. Backstrom, C. Marlow, and J. Kleinberg, “Structural Diversity in Social Contagion,” Proceedings of the National Academy of Sciences 109, no. 16 (April 17, 2012): 5,962-5,966; and M. Karsai, G. Iñiguez, R. Kikas, K. Kaski, and J. Kertész, “Local Cascades Induced Global Contagion: How Heterogeneous Thresholds, Exogenous Effects, and Unconcerned Behaviour Govern Online Adoption Spreading,” Scientific Reports 6, no. 27178 (June 7, 2016).

12. R.S. Burt, “Structural Holes: The Social Structure of Competition” (Cambridge: Harvard University Press, 1992).

13. S.E. Page, “The Difference: How the Power of Diversity Creates Better Groups, Firms, Schools, and Societies” (Princeton, N.J.: Princeton University Press, 2007); and Hansen, “The Search-Transfer Problem.”

14. J.F. Padgett and C.K. Ansell, “Robust Action and the Rise of the Medici, 1400-1434,” American Journal of Sociology 98, no. 6 (May 1993): 1,259-1,319.

15. G. Simmel, “Sociology of Georg Simmel,” ed. K.H. Wolff (New York: Free Press, 1950); and D. Krackhardt, “The Ties That Torture: Simmelian Tie Analysis in Organizations,” Research in the Sociology of Organizations 16, no. 1 (January 1999): 183-210.

16. Hansen, “The Search-Transfer Problem”; and D.G. Ancona and D. Caldwell, “Bridging the Boundary: External Activity and Performance in Organizational Teams,” Administrative Science Quarterly 37, no. 4 (December 1992): 634-665.

17.M. de Vaan, B. Vedres, and D. Stark, “Game Changer: The Topology of Creativity,” American Journal of Sociology 120, no. 4 (January 2015): 1,144-1,194; and R. Reagans and B. McEvily, “Network Structure and Knowledge Transfer: The Effects of Cohesion and Range,” Administrative Science Quarterly 48, no. 2 (June 2003): 240-267.

18.G. Davis and H. Greve, “Corporate Elite Networks and Governance Changes in the 1980s,” American Journal of Sociology 103, no. 1 (July 1997): 1-37.