• Watts, Preface and Chapter 1. (Available from Canvas)
• Milgram (1967). The small world problem. Psychology Today, 1:62-67. (Available from Canvas)
• Travers and Milgram (1969). An experimental study of the small world problem. Sociometry, 32(4):425-443.
• Kleinfeld (2002). The small world problem. Society, 39(2):61-66.

More on the small world problem and some history (02/03/25)

• Granovetter (2003). Ignorance, knowledge, and outcomes in a small world. Science, 301:773-774.
• Dodds, Muhamad, and Watts. (2003). An experimental study of search in a global social networks. Science, 301:827-829.
• Watts, Chapter 2. (Available from Canvas)
• Erdos-Reyni random graph animation by Uri Wilensky. (optional)

Understanding the small world phenomena (02/05/25)

• Watts, Chapter 3.
• Watts and Strogatz (1998). Collective dynamics of 'small-world' networks. Nature 393, 440-442.
• Victor (2011). Scientific Communication As Sequential Art.
• Watts (1999). Networks, dynamics, and the small world phenomenon. American Journal of Sociology, 105(2):493-527.

Degree distributions and power laws (02/10/25)

• Watts, Chapter 4, 101-114.
• Barabasi and Bonabeau (2003) Scale-free networks. Scientific American, 50-59. (Available from Canvas)
• Barabasi and Albert (1999) The emergence of scaling in random networks. Science, 286:509-512.
• Liljeros et al. (2001). The web of human sexual contacts. Nature, 411:907-908 with comment and rejoinder.

Foci (02/12/25)

• Gladwell (1999). Six degrees of Lois Weisberg. The New Yorker. (Available on Canvas)
• Watts, Chapter 4, 114-129. (Available on Canvas)
• Feld (1981) The focused organization of social ties. American Journal of Sociology, 86(5):1015-1035.

Social search (02/17/25)

• Watts, Chapter 5.
• Lee (1969). The Search for an Abortionist: Preface, Chapter 1, and Chapter 5. (Available from Canvas).

Spread of disease in networks (02/19/25)

• Watts, Chapter 6.
• Bearman et al. (2004). Chains of affection: The structure of adolescent romantic and sexual networks. American Journal of Sociology, 110(1):44-91.

The madness of crowds (02/24/25)

• Watts, Chapter 7.
• Asch (1955). Opinions and social pressure. Scientific American, 193(5):31-35. (Available on Canvas)
• Easley and Kleinberg (2010). Networks, Crowds, and Markets: Chapter 16 (Sec 16.1, 16.2, and 16.7).
• Tierney (2007). Diet and fat: A severe case of mistaken consensus. New York Times.

Thresholds, cascades, and predictability (02/26/25)

• Gladwell (1996). The tipping point. The New Yorker. (Available on Canvas)
• Watts, Chapter 8.
• Watts (2002). A simple model of global cascades on random networks. Proceedings of the National Academy of Sciences 99:5766-5771.

Cascades and fads in cultural markets (03/03/25)

• Hedstrom (2006). Experimental macro sociology: Predicting the next best seller. Science, 311:786-787.
• Salganik, Dodds, and Watts (2006). Experimental study of inequality and unpredictability in an artificial cultural market. Science, 311:854-856.
• Salganik and Watts (2008). Leading the herd astray: Experimental study of self-fulfilling prophecies in an artificial cultural market. Social Psychology Quarterly, 71:338-355.

Midterm exam

• 60 minute midterm exam.

Spring break

• Have a safe and restful break.

Core discussion networks and loneliness (03/17/25)

• Marsden (1985). Core discussion networks of Americans. American Sociological Review, 52(1):122-131. .
• Lee et al. (2023). Transformation of social relationships in COVID-19 America: Remote communication may amplify political echo chambers. Science Advances 9(511):1-14. .
• Murthey (2023). Surgeon General: We Have Become a Lonely Nation. It’s Time to Fix That. New York Times .

Strength of weak ties and finding a job (03/19/25)

• Granovetter, M. (1973). The strength of weak ties. American Journal of Sociology, 78(6), 1360-1380.
• Wang and Uzzi (2022). Weak ties, failed tries, and success. Science, 377(6612), 1256-1258.
• Rajkumar et al. (2022). A causal test of the strength of weak ties. Science, 377(6612), 1304-1310.
• Singer (2022) LinkedIn Ran Social Experiments on 20 Million Users Over Five Years New York Times.

Social networks and social capital (03/24/25)

• Reeves and Fall (2023) Seven key takeaways from Chetty’s new research on friendship and economic mobility Brookings Instution.
• Angrist and Sacerdote (2022) The social connections that shape economic prospects. Nature 608, 37-38.
• Chetty et al. (2022) Social capital I: measurement and associations with economic mobility. Nature 608, 108-121.
• Chetty et al. (2022) Social capital II: determinants of economic connectedness. Nature 608, 122-134.

Social encounters and turning points (03/26/25)

• Bandura (1982). The Psychology of Chance Encounters and Life Paths. American Psychologist.
• Goffman (2019). Go to More Parties? Social Occasions as Home to Unexpected Turning Points in Life Trajectories. Social Psychology Quarterly 82(1):51-74.

Social media and individuals (03/31/25)

• Kross et al. (2021). Social media and well-being: Pitfalls, progress, and next steps. Trends in Cognitive Science.
• Carey (2019). This is your brain off Facebook. New York Times.
• Allcott et al. (2020). The welfare effects of social media. American Economic Review.
• Baym et al. (2020). Mindfully scrolling: Rethinking Facebook after time deactived. Social Media + Society.

Social media and society (04/02/25)

• Crokett (2017). Moral outrage in the digital age. Nature Human Behavior.
• Brady et al. (2021). How social learning amplifies moral outrage expression in online social networks. Science Advances.
• Aral (2018). How lies spread online. New York Times.
• Vosoughi et al. (2018). The spread of true and false news online. Science.
• William Brady (2024) Bluesky thread about paper: "Misinformation exploits outrage to spread online".
• Molly Crockett (2024) Bluesky thread about creating the paper: "Misinformation exploits outrage to spread online".
• McLoughlin et al. (2024) Misinformation exploits outrage to spread online. Science 386(6725):991-996.

Social media and democracy (04/07/25)

• Stroud et al. (2020). A Proposal for Understanding Social Media's Impact on Elections: Rigorous, Peer-Reviewed Scientific Research Medium blog post.
• Guess et al. (2023). How do social media feed algorithms affect attitudes and behavior in an election campaign? Science. 381(6656):398-404.
• Kupferschmidt (2024). A study found Facebook's algorithm didn't promote political polarization. Critics have doubts. Science.
• Bagchi et al. (2024) Social media algorithms can curb misinformation, but do they? Science, eletter.
• Guess et al. (2024) Response to "Social media algorithms can curb misinformation, but do they?" Science, eletter.
• Understanding How and When Information Spread on Facebook During the 2020 Election, video from University of Pennsylvania features Sandra González-Bailón.
• González-Bailón et al. (2024) The Diffusion and Reach of (Mis)Information on Facebook During the U.S. 2020 Election. Sociological Science 11(41):2330-6696.

Fixing social media (04/09/25)

• Frank (2021). The economic case for regulating social media. New York Times.
• Pennycook and Rand (2020). The right way to fight fake news. New York Times.
• Bail et al. (2018). Exposure to opposing views on social media can increase political polarization. PNAS.
• Kaiser et al. (2021). Warnings that work: Combating misinformation without deplatforming. Lawfare.
• Kaiser et al. (2021). Adapting security warnings to counter online disinformation. 30th USENIX Security Symposium (USENIX Security 21).

Obesity is contagious . . . maybe (04/14/25)

• Thompson, C. (2009). Are your friends making you fat? New York Times Magazine, September 13.
• Watch James Fowler on The Colbert Report.
• Christakis, N.A. and Fowler, J.H. (2007). The spread of obesity in a large social network over 32 years. New England Journal of Medicine, 357:370-379.
• Johns, D. (2011). Disconnected? Slate.
• Lyons, R. (2011). The spread of evidence-poor medicine via flawed social-network analysis. Statistics, Politics and Policy, 2(1): Article 2.
• Gelman (2024) Here's a useful response by Christakis to criticisms of the contagion-of-obesity claims. Blog post.

Experimental studies of contagion (04/16/25)

• Nickerson, D.W. (2008). Is voting contagious? Evidence from two field experiments. American Political Science Review, 102(1):49-57.v
• Kramer, A.D.I. et al. (2014). Experimental evidence of massive-scale emotional contagion through social networks. Proceedings of the National Academy of Sciences.

Complex contagion (04/21/25)

• Gladwell (2010). Small change: The revolution will not be tweeted. New Yorker.
• Centola and Macy (2007). Complex contagion and the weakness of long ties. American Journal of Sociology, 113(3):702-734.
• Centola (2010). The spread of behavior in an online social network experiment. Science, 329(5996):1194-1197.

Seeding social change (04/23/25)

• Huber (2016) Students with influence over peers reduce school bullying by 30 percent. Princeton Univesrity website.
• Paluck et al. (2016) Changing climates of conflict: A social network driven experiment in 56 schools. Proceedings of the National Academy of Sciences 113(3):566-571.
• Cummings (2024) Targeting friends to induce social contagion to benefit the world. Yale Univesrity website.
• Airoldi and Christakis (2024). Induction of Social Contagion Across Diverse Outcomes in Structured Experiments in Isolated Honduras Villages. Science

This work is licensed under a Creative Commons Attribution 4.0 International License.