Welcome to Michael Macy's Website

A Structural Learning Model of Cultural Polarization

“Why on earth," asks Steven Pinker in The Blank Slate, "should people's beliefs about sex predict their beliefs about the size of the military? What does religion have to do with taxes? Whence the linkage between strict construction of the Constitution and disdain for shocking art?” A simple toy model of opinion cascades on a dynamic network suggests an answer: People are attracted to those with similar cultural preferences, repelled by those with salient differences, and are positively and negatively influenced by those to whom they are attracted/repelled. The model consists of 100 fully connected agents with initially random traits on 10 cultural dimensions. The axes displayed above are the two principle eigenvectors from the 10-dimensional opinion matrix. The size of the circle indicates the number of agents with that cultural profile. Multiple runs show how the dynamics of social influence, homophily, and xenophobia can lead to cultural polarization, such that agents at each pole have identical traits on all ten cultural dimensions and are maximally dissimilar to the "outgroup" at the opposite pole. Thus, from a random start, all 45 pairwise cultural dimensions come to be highly correlated, but the signs of the correlations are in all cases entirely arbitrary. Incomplete polarization is also possible, with agents aligned on a small number of cross-cutting dimensions. The model's results were recently confirmed in a laboratory experiment with human subjects (click here).

Michael W. Macy

Goldwin Smith Professor of Arts and Sciences

Department of Sociology

Department of Information Science

Director, Social Dynamics Laboratory

Cornell University

Ithaca, NY 14853

Voice: (607) 255-4269

Fax: (607) 202-4913

Email: mwm14@cornell.edu

CV: Click Here

Click here for New York Times Op Ed discussion of  our PNAS paper on "Polarization and Tipping Points"

Click here for interview on Medhi Hasan Show 

Click here for quote about "the tipping point" on CNN's "The Lead with Jake Tapper"

Click here for Nature feature story by Jim Giles on computational social science at Cornell

Click here for Oct 2011 "Naked Scientist" interview on BBC

Click here for Seti Institute's "Big Picture Science" interview on Public Radio

Click here for March 2014 NY Times Op Ed "The Science of Paying It Forward"

Click here for Guardian article on "Partisan Consumption of Science"

Click here or here for "Science Friday" interview

Click here for our lifestyle-politics.com website

Why does our world not degenerate into the world of Mad Max -- and why does it sometimes seem as if it may? Social order can be imposed "from above" by a global policing mechanism or it can emerge "from below" through local interactions with no centralized coordination. Suppose no member of the population has the ability to identify or impose a global solution. How then is social order possible? My research explores how norms, opinions, emotions, and collective action emerge and spread through local interaction. The motivating problem is one that defines the human condition: the overwhelming need for norms that constrain aggressive and mutually destructive behavior is no guarantee that such rules will emerge or be obeyed by anyone except a few "suckers." On the contrary, norms can even make matters worse, by obligating people to engage in behaviors that are individually and collectively harmful (e.g., pressuring one's neighbors to cheer a "naked emperor"). Our research team uses computational models, laboratory experiments with human subjects, and "big data" from online networks to look for elementary principles of social interaction that may yield clues about possible answers to these and related puzzles about human behavior and social interaction. A wine-tasting study with Robb Willer and Ko Kuwabara showed that participants not only rated a vinegar-tainted wine over one that was untainted but also publicly rated fellow wine tasters higher who agreed. However, when  the ratings were private, participants revealed their true beliefs. The public pressure  for "false enforcement" is a "complex  contagion" that  depends on social reinforcement from multiple neighbors. Follow-up studies with Damon Centola, Vladimir Barash, and Chris Cameron showed how complex contagions depend initially on dense local structure but once the contagion achieves a critical mass, diffusion can leverage the long-range ties characteristic of small world networks. In another small-worlds study (with Nathan Eagle and Rob Claxton) using a nearly complete set of telephone logs from the UK we found that small worlds are associated with economic development. A related study with Patrick Park and Joshua Blumenstock used global online phone and social media networks to reveal "social wormholes" that create high-bandwidth connections across vast network distances. 

These studies used digital traces of behavior to observe global patterns that would be difficult or even impossible to measure using  conventional sources of observational data such as surveys. For  example, Scott Golder and I analyzed the affective content of global Twitter messages to reveal remarkable similarity in diurnal and seasonal mood variations across diverse cultures. A follow-up study with Minsu Park and colleagues at Spotify used global streaming logs to reveal similar patterns in the emotions people experience through music. Recent research has focused on political polarization. Daniel Della-Posta, Yongren Shi and I wondered why liberals drink lattes, and a study with Bill Shi, Yongren Shi, Fedor Dokshin and James Evans shows how polarization extends even to the consumption of books on popular science.

I have listed below some of my papers that you are welcome to download:

Political polarization of news media and influencers on Twitter in the 2016 and 2020 US presidential elections

James Flamino, Alessandro Galezzi, Stuart Feldman, Michael Macy, Brendan Cross, Zhenkun Zhou, Matteo Serafino, Alexandre Bovet, Hernan A Makse, and Boleslaw K Szymanski

Nature Human Behaviour, 2023

Fighting bias with bias: How same-race endorsements reduce racial discrimination on Airbnb

Minsu Park, Chao Yu, and Michael W. Macy

Science Advances 9 (6), eadd2315

Polarization and Tipping Points

Michael W. Macy, Manqing Ma, Daniel R. Tabin, Jianxi Gao, and Boleslaw K. Szymanski

Proceedings of the National Academy of Sciences,  2021, 118: e2102144118

Threshold Models of Collective Behavior II: The Predictability Paradox and Spontaneous Instigation

Michael Macy and Anna Evtushenko 

Sociological Science, 7: 628-648, 2020

Opinion Cascades and the Unpredictability of Partisan Polarization

Michael Macy, Sebastian Deri, Alex Ruch, and Natalie Tong

Science Advances, August, 2019

The Strength of Long-Range Ties in Population Scale Social Networks

Patrick Park, Joshua Blumenstock, and Michael Macy

Science, 362: 1410–13, 2019

It’s not just how the game is played, it’s whether you win or lose

Mario D. Molina, Mauricio Bucca, and Michael W. Macy

Science Advances 5: eaau1156, 2019

The Opacity Problem in Social Contagion

George Berry, Christopher Cameron, Patrick Park, and Michael Macy

Social Networks 56:93-101, 2019

Global Music Streaming Data Reveals Diurnal and Seasonal Patterns of Affective Preference

Minsu Park, Jennifer Thom, Sarah Mennicken, Henriette Cramer, and Michael Macy

Nature Human Behaviour, Dec. 2018

Peer effects on adolescent smoking: Are popular teens more influential?

Juan David Robalino and Michael Macy

Plos One July, 2018

Cultural Fault Lines and Political Polarization

Yongren Shi, Kai Mast, Ingmar Weber, Agrippa Kellum, and Michael Macy

Proceedings of the 2017 ACM on Web Science, pp. 213-217

Bots as Virtual Confederates: Design and Ethics

Peter Krafft, Michael Macy, Sandy Pentland

Proceedings of CSCW 2017

The Local Dynamics of Institutional Change

Chris Cameron and Michael Macy

Rationality and Society 2017

Millions of Online Book Co-purchases Reveal the Politicization and Polarization of U.S. Science

F. Bill Shi, Yongen Shi, Fedor Dokshin, James Evans and Michael Macy.

Nature Human Behaviour 2017

Automated Hate Speech Detection and the Problem of Offensive Language

Tom Davidson, Dana Warmsly, Ingmar Weber, and Michael Macy.

Proceedings of the ICWSM 2017.

Complex Contagions and the Diffusion of Popular Twitter Hashtags in Nigeria

Clay Fink, Aurora Schmidt, Vlad Barash, Chris Cameron, and Michael Macy.

Social Network Analysis and Mining, December 2016, 6:1

Investigating the Observability of Complex Contagion in Empirical Social Networks

Clay Fink, Aurora Schmidt, Vlad Barash, John Kelly, Chris Cameron, and Michael Macy

Proceedings of ICWSM 2016

Measuring Structural Similarity in Large Online Networks

Yongren Shi and Michael Macy

Social Science Research 2016

Embracing Cultural Diversity: Online Social Ties in Distributed Workgroups

Wei Dong, Kate Ehrlich, Michael Macy, and Michael Muller.

Proceedings of CSCW 2016

The Center Cannot Hold

Daniel DellaPosta and Michael Macy

In Order on the Edge of Chaos, Cambridge University Press, 2016.

Why Do Liberals Drink Lattes?

Daniel Della Posta, Yongren Shi, and Michael Macy

American Journal of Sociology, March, 2015

The Mesh of Civilizations in the Global Network of Digital Communication

Bogdan State, Patrick Park, Ingmar Weber, and Michael Macy

PLOS ONE, May 29, 2015

The Social Contagion of Anti-Social Behavior

Milena Tsvetkova and Michael Macy

Sociological Science, Feb. 10, 20

Big Theory: A Trojan Horse for Economics?

Michael Macy

Review of Behavioral Economics 2014

The Signal Importance of Noise

Michael Macy and Milena Tsvetkova

Sociological Methods and Research 2015

Digital Footprints: Opportunities and Challenges for Social Research

Scott Golder and Michael Macy

Annual Review of Sociology, Vol. 40, 2014

The Social Contagion of Generosity

Milena Tsvetkova and Michael Macy

PLOS One Feb. 13, 2014: 9(2): e87275

Statistical Mechanics and Social Sciences

Santo Fortunato, Michael Macy, Sidney Redner

Journal of Statistical Physics 2013, 151:1-8

Critical Phenomena in Complex Contagions

Vladimir Barash, Chris Cameron, and Michael Macy

Social Networks 2012, 34:451-61

Diurnal and Seasonal Mood Vary with Work, Sleep and Daylength Across Diverse Cultures

Scott Golder and Michael Macy

Science 2011, 333:1878-81

Small Worlds and Cultural Polarization

Andreas Flache and Michael Macy

Journal of Mathematical Sociology 2011, 34: 146-76

Local Convergence and Global Diversity: From Interpersonal to Social Influence

Andreas Flache and Michael Macy

Journal of Conflict Resolution 2011, 55: 970-95

Network Diversity and Economic Development

Nathan Eagle, Rob Claxton, and Michael Macy

Science 2010, 328: 1029-1031

Computational Social Science

David Lazer et al.

Science 2009, 323: 712-723

The False Enforcement of Unpopular Norms

Rob Willer, Ko Kuwabara, and Michael Macy

American Journal of Sociology 2009, 115:451-490

Neighborhood Chance and Neighborhood Change

Arnout Van de Rijt, David Siegel, and Michael Macy

American Journal of Sociology 2009, 114:1166-80

Complex Contagions and the Weakness of Long Ties

Damon Centola and Michael Macy

American Journal of Sociology 2007, 113:702-34

Culture, Identity, and Structure in Social Exchange: A Web-based Trust Experiment in the U.S. and Japan

Kuwabara, K., R. Willer, M. Macy, R. Mashima, S. Terai, and T. Yamagishi

Social Psychology Quarterly, 2007, 70:461-79

Collective Action and the Empirical Content of Stochastic Learning Models

M. Macy and A. Flache

American Journal of Sociology, 2007, 112: 1546-54

Cascade Dynamics of Complex Propagation

Damon Centola, Victor M. Eguiluz, and Michael Macy

Physica A 2007, 374: 449-456

Power and Dependence in Intimate Exchange

Arnout van de Rijt, and Michael Macy

Social Forces 2006, 84:1455-70

Ethnic Preferences and Residential Segregation: Theoretical Explorations Beyond Detroit

Michael Macy and Arnout van de Rijt

Journal of Mathematical Sociology 2006, 30: 275-88

The Emperor's Dilemma: A Computational Model of Self-Enforcing Norms

Damon Centola, Robb Willer, and Michael Macy

American Journal of Sociology 2005, 110:1009-40

Social Life in Silico: The Science of Artificial Societies

Damon Centola and Michael Macy

Handbook of Group Research and Practice 2005, pp. 273-2812

Power, Identity, and Collective Action in Social Exchange

Brent Simpson and Michael Macy

Social Forces, June, 2004.

Polarization in Dynamic Networks: A Hopfield Model of Emergent Structure

Michael Macy, James Kitts, Andreas Flache, and Steve Benard

Dynamic Social Network Modeling and Analysis, National Academy Press, 2003

Learning Dynamics in Social Dilemmas

Michael Macy and Andreas Flache

Proceedings of the National Academy of Sciences, May 14, 2002.

Stochastic Collusion and the Power Law of Learning

Andreas Flache and Michael Macy

Journal of Conflict Resolution, October, 2002

From Factors to Actors: Computational Sociology and Agent-Based Modeling

Michael Macy and Robert Willer

Annual Review of Sociology, Vol. 28, 2002

Trust and Market Formation in the U.S. and Japan

Michael Macy and Yoshimichi Sato

Proceedings of the National Academy of Sciences, April, 2002

Social Simulation

Michael W. Macy

In N. Smelser and P. Baltes, eds., International Encyclopedia of the Social and Behavioral Sciences, Elsevier, 2002

Dependence and Cooperation in Fuzzy Dilemmas: The Effects of Environmental and Endowment Uncertainty

R. Thomas Boone and Michael W. Macy

In R. Suleiman, D. Budescu, & D. Messick, eds., ContemporaryPsychological Research on Social Dilemmas

Cambridge University Press, 2002.

'In Search of Excellence': Fads, Success Stories, and Adaptive Emulation*

David Strang and Michael Macy

Best Paper Proceedings of the 1999 Academy of Management Conference, Chicago,IL

American Journal of Sociology, July, 2001.

*HTML Preprint not identical to published version

Collective Action and Power Inequality: Coalitions in Exchange Networks*

Brent Simpson and Michael Macy

Social Psychology Quarterly, March, 2001.

Structural Learning: Attraction and Conformity in Task-Oriented Groups

James Kitts, Michael Macy, and Andreas Flache

Computational and Mathematical Organization Theory, 1999, vol. 5(2):129-45.

Unlocking the Doors to Prisoners Dilemma: Dependence, Selectivity, and Cooperation

R. Thomas Boone and Michael Macy

Social Psychology Quarterly 1999, 62: 32-52.

The Evolution of Trust and Cooperation between Strangers: A Computational Model*

Michael Macy and John Skvoretz

American Sociological Review, October, 1998

Presented at the Sante Fe Institute, August 6, 1996

Social Order and Emergent Rationality

Michael Macy

In A. Sica, ed. Whatis Social Theory: The Philosophical Debates, 1998, Blackwell.

Dependence and Cooperation in the Game of Trump

R. Thomas Boone and Michael Macy

Advances in Group Processes, vol. 15, 1998

Social Order in an Artificial World

Michael W. Macy

Journal of Artificial Societies and Social Simulation, January, 1998.

The Weakness of Strong Ties II: Collective Action Failure in a Self-Organizing Social Network

Michael Macy , James Kitts, and Andreas Flache

Presented at American Sociological Association, Toronto, August 11, 1997.

Identity, Interest, and Emergent Rationality: An Evolutionary Synthesis

Michael Macy

Rationality and Society, vol. 9, 1997.

The Weakness of Strong Ties: Collective Action Failure in a Highly Cohesive Group

Andreas Flache and Michael W. Macy

Journal of Mathematical Sociology, June, 1996

Natural Selection and Social Learning in Prisoner's Dilemma: Co-adaptationwith Genetic Algorithms and Artificial Neural Networks

Michael W. Macy

Sociological Methods and Research, Vol 25, August, 1996, pp. 103-137

Beyond Rationality in Models of Choice

Michael W. Macy and Andreas Flache

Annual Review of Sociology, Vol. 21, 1995

PAVLOV and the Evolution of Cooperation: An Experimental Test

Michael W. Macy

Social Psychology Quarterly, June, 1995

Artificial Social Intelligence

William Bainbridge, Edward Brent, David Heise, Michael Macy, Barry Markovsky, & John Skvoretz

Annual Review of Sociology, Vol. 21, 1995

Once Upon a Time There Was a Suboptimal Equilibrium

Michael W. Macy

The Agora, June, 1996

Cowardly Lions: Genetic Programming or Social Learning?

Michael W. Macy

The Agora, December, 1995

Social Class

Michael W. Macy

The Encyclopedia of Language and Linguistics

Backward-Looking Social Control

Michael W. Macy

American Sociological Review, 1993, Vol. 58:819-36.

Chains of Cooperation: Threshold Effects in Collective Action

Michael W. Macy

American Sociological Review, 1991, Vol. 56:730-47.

Learning to Cooperate: Stochastic and Tacit Collusion in Social Exchange

Michael W. Macy

American Journal of Sociology, 1991, Vol. 97:808-43.

Learning Theory and the Logic of Critical Mass

Michael W. Macy

American Sociological Review, 1990, Vol. 55:809-26.

Value Theory and the Golden Eggs: Appropriating the Magic of Accumulation

Michael W. Macy

Sociological Theory, 1988, Vol. 6: 131-52.