I study solidarity and cooperation in diverse communities and have projects in New York City, Milan, and Eastern Germany investigating the relationship between ethnic heterogeneity and collective outcomes. I use an experimental approach (field, lab-in-the-field behavioral games, and natural experiments) to answer three groups of questions:

1) In-group/Out-group Dynamics: What is the effect of out-group exposure? what explains variation in levels of prosocial behavior across communities? and what is the relationship between in-group and out-group prosociality?

2) Diversity and Social Differentiation: To what extent ethnicity, rather than poverty affect prosocial behavior? How do discrimination and social deference take place in everyday life?

3) Types of interactions and mechanisms: How do natives, minorities and immigrants behave in different types of interactions? What mechanisms bring about cooperation in heterogeneous communities?

Generalized or Parochial Altruism? Evidence from a Nationwide Lost-Letter Experiment”, under review.

Strangers in Hostile Lands: Exposure to Refugees and Right-wing Support”. (with M. Schaub and J. Gereke), under review.

2019 “Does Poverty Undermine Cooperation in Multiethnic Settings? Evidence from a Cooperative Investment Experiment”, Journal of Experimental Political Science, 1-14. (with M. Schaub and J. Gereke)

2018 “Ethnic diversity, poverty and social trust in Germany: Evidence from a behavioral measure of trust”, PLOS ONE, 13(7). (with J. Gereke and M. Schaub)

2015 “Love thy Neighbor? Ethnoracial Diversity and Trust Reexamined”, American Journal of Sociology, 121(3): 722-782. (with M. Abascal)


American politics over the last four decades has been characterized by increased partisanship in Congress and growing polarization of the political debate. However, we still do not fully know how mass opinion has responded to elite polarization.

Picture 1.png

Based on a conception of political division as a process of ideational and relational alignment that splits the polity into opposite camps, my work does not simply provide a systemic account of political change, but also captures the micro-level tensions that ordinary citizens experience in an era of increased political partisanship. For instance, Americans have become politically more divided yet people with different political views live, work, and spend time together. How do people deal with the conflicting political views within their social networks? Moreover, party alignment along moral and economic issues has made it difficult for certain socio-demographic profiles to define their political allegiance: Will a wealthy, secular individual identify with the Republican party's economic views, or with the Democratic party's moral views?


Centrifugal Politics, Crosscutting People: The Demographic and Social Network Bases of Partisanship in American Public Opinion,” advance contract with Princeton University Press (co-published with the Russell Sage Foundation).

[2019] “Polarization and Secular Trends in U.S. Public Opinion”, Journal of Politics, forthcoming. (with B. Park)

2017 " 'It could turn ugly': Selective Disclosure of Political Views and Biased Network Perception,” Social Networks, 52:1-17. [lead article]  (with S. Cowan).

2014 “Neither Ideologues, nor Agnostics: Alternative Voters’ Belief System in an Age of Partisan Politics,”  American Journal of Sociology, (with A. Goldberg).

2011 “Partisan Joiners: Associational Membership and Political Polarization in America (1974-2004),” Social Science Quarterly, 92(3): 631-655. 

2008 “Partisans Without Constraint: Political Polarization and Trends in American Public Opinion,” American Journal of Sociology, 114(2): 408-46 (with A. Gelman).

2007 “Dynamics of Political Polarization,” American Sociological Review, 72: 784-811 (with P. Bearman). 


Development scholars regard farmer organizations as a core component of poverty reduction strategies, but little is known about the social dynamics that make certain producer organizations more successful than others. In collaboration with Guy Grossman, I have conducted an extensive research to study how producer organizations solve classic problems of collective action.

picture 2.png

Adopting an innovative methodological framework that combines “lab in the field” behavioral experiments with observational data, we gathered extensive information on 50 producer organizations, administered more than 3,000 individual level interviews, and collected social network information for each of our subjects. In addition, we took a series of behavioral experiments, typically conducted in a laboratory environment, to the field, and performed our research with members of pre-existing groups – farmer cooperatives – that face collective action problems on a regular basis. The farmer groups we studied were created as part of the Uganda’s largest recent rural development intervention – the Agriculture Productivity Enhancement Project (APEP) –, whose goal was to support small farmers integration into commercial farming, exploit economies of scale and bargain for better prices.

In general, we can distinguish between two types of solutions to collective action problems: (a) centralized solutions, in which a leader or small elite are the locus of coordination, control and enforcement of cooperative efforts, and (b) decentralized solutions, in which cooperation emerges from loosely coordinated efforts, via social networks. Whereas centralized solutions rely on legitimate authority and the threat of punishment, cooperation in decentralized solutions is sustained through mechanisms of direct and indirect reciprocity, and peer-pressure. This research addresses both aspects.


2015 “Cooperative Networks: Altruism, Group Solidarity, Reciprocity and Sanctioning in Ugandan Farmer Organizations,American Journal of Sociology.

2013 “The Effect of Group Attachment and Social Position on Prosocial Behavior. Evidence from Lab-in-the-Field Experiments,PLOS ONE, 8(3) (with G. Grossman).

2012 “The Impact of Elections on Cooperation: Evidence from a Lab in the Field Experiment in Uganda,” American Journal of Political Science, 56(4): 964-985 (with Guy Grossman)

2011 “Centralized Sanctioning and Legitimate Authority Promote Cooperation in Humans", Proceedings of the National Academy of Sciences, 108(27): 11023-11027 (with Guy Grossman).


Group cooperation and social division are two sides of the same coin: as people come together to form groups, they also separate themselves from others. Both cooperation and division originate from the activity of individuals and groups acting on the basis of their interests and partisan views of what society ought to be. By studying social actors at the intersection of the social categories and relational networks to which they belong, I aim to capture the dynamics of identity formation and social influence that trigger economic and political action and to connect attitudinal changes to broader processes of interest representation and public goods provision.


In this macro area of research I combine a long-term interest in formal models of collective action and dynamics of group formation with the empirical study of different forms of political coordination (e.g., by looking at the structural features of civic networks in Glasgow and Bristol, at the divisive patterns of associational membership in America, and at the construction of consent in the LGBT movement).

2011 “Cultural Anchors and the Organization of Difference: A Multi-method Analysis of LGBT Marches on Washington,” American Sociological Review, 76: 179-206. [lead article] (with Amin Ghaziani)

2011 “Partisan Joiners: Associational Membership and Political Polarization in America (1974-2004),Social Science Quarterly, 92(3): 631-655. 

2009 “Collective Action” in P. Hedström and P. Bearman (eds.) The Oxford Handbook of Analytical Sociology.

2007 “The Integrative Power of Civic Networks,” American Journal of Sociology, 113(3): 735-80 (with M. Diani).

2007 “Dynamics of Political Polarization,” American Sociological Review, 72: 784-811 (with P. Bearman). 

2005 “Oltre il free rider: l’utilizzo di modelli formali nello studio dell’azione collettiva,” Rassegna Italiana di Sociologia, 40,1: 125-156. En. title: “Beyond Free Riding: On the Use of Formal Models for the Study of Collective Action.”


The vast majority of sociologists dismiss rational choice theory (RCT) as inadequate for its assumption of a selfish actor and for its reliance on optimization strategies. However they rarely provide an alternative: Most sociologists either do not spell out how decisions are made, or rely on decision making processes that still include some sort of utility maximization. In contrast, research programs in cognitive psychology and decision science have developed computational models of adaptive decision making that rely on fast and frugal heuristics, a set of satisfacing strategies that do not require a large amount of information (frugal) and rely on reasoning algorithms that are very simple and rapid (fast). Inspired by this research, I approached the study of voting behavior asking what are the judgment processes that regular citizens use in making up their mind about politics given the capacity of the human mind, and the constraints of the social environment in which they operate.   


2012 “The Simple Art of Voting. The Cognitive Shortcuts of Italian Voters”, Oxford University Press.

2006 “Voter Heuristics and Political Cognition in Italy: An Empirical Typology”, Electoral Studies, 25: 448-466 (with H.M.A. Schadee).

2004 “Il fascino della coalizione. Come e perche' le alleanze elettorali influenzano il modo in cui gli elettori interpretano la politica,” Rivista Italiana di Scienza Politica, 34, 2: 249-276 (with H.M.A. Schadee). En. title: “The Appeal of Coalitions: How and Why Electoral Alliances Affect Voters’ Political Understanding.”

2003 “Il voto ideologico esiste? L’utilizzo delle categorie di sinistra e destra nell’elettorato italiano”, Quaderni dell’Osservatorio Elettorale, 49: 5-34. En. title: “Does the Ideological Voter Exist?: The Use