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Diego Gambetta

For prospective students

I supervise dissertations with an analytical approach, and a mix of behavioural theory and empirical data, including data from lab and field experiments. My supervisees’ research topics cover several areas, including the determinants and consequences of cooperation, conflict, corruption, inter-ethnic relations, migration, indebtedness, and political preferences.

My current interests focus on:

  • the behavioural traits of violent extremists
  • signalling and communication, especially when beset by deception;
  • trust and cooperation (or their obverse, distrust and cheating), in various domains—economic development, conflict and criminal markets;

Research Projects

On extremists

After completing Engineers of Jihad. The Curious Connection between Education and Extremism (with Steffen Hertog, Princeton University Press 2016), I have now plans to test experimentally some of the findings of the book.

On Signalling, Trust and Cooperation

I am pursuing two theoretical strands that I developed in Codes of the Underworld: How criminals Communicate (in chapters 3 and 4).

One project, with Aron Szekely, investigates experimentally how the amount of information on an opponent’s ‘toughness’ affects the chances that a conflict over scarce resources between two individuals results into a ‘fight’. The design aims at capturing situations, such as those found in prisons, in which there are no enforceable rules of allocation and in which ‘might is right’, and to find out how much order vs violent conflict emerges. We measure toughness by asking subjects to do a wall-sit for as long as they can resist. The information on how long they resisted is then revealed to the opponent who decides whether to challenge or ignore. If he challenges the other player may yield or resist. If he resists a fight ensues and yields a winner and a loser. We conjecture that when information on fighting prowess grows fighting decreases, exploitation does not increase, and fighting does not decrease among equally ‘tough’ subjects. We ran the experiment in the Bologna lab and we are in the process of writing up the results, including some implications on prison policy.

The other project posits that even in unpromising circumstances, such as interactions among criminals, some cooperation can be established if subjects exchange compromising information; this is information that once revealed would trigger punishment by a third party, such as the law or the community. I tested this with Jennifer Flashman (see publications below) using survey data to see whether deviant adolescent are especially likely to make friends with each other, over and above what activity-based homophily would predict. With Wojtek Przepiorka, we have designed an experimental test to see whether we can induce cooperation among those who behave as ‘villains’ in the experiment and who have thus reason to distrust each other and not to cooperate. We ran the experiment in March 2016; we plan to publish the results in the near future.

I am team-member of ‘Strangers’ (www.strangers.it), a project funded by the European Research Council for 2010-2014, and led by Marco Casari, an experimental economist at the University of Bologna. The project explores the behavioural differences between North and South Italy, a much conjectured phenomenon never before researched experimentally. Italy is an ideal case for a within-country study on development: since its unification in 1861 the country’s institutions are shared, yet there exists a persisting North-South gap along many social and economic dimensions. We ran a controlled lab-in-field experiment in four Italian cities, two in the North and two in the South, with a representative sample of the population (N=618). To study dispositions toward cooperation, altruism, and risk their experiment comprised a “Public Good” (PGG) experiment and a “Trust Game” (TG); individual tasks consisted of a choice over a set of lotteries and three modified dictator games (DG). The core results have been published in 2016 (see publications below). We are now planning another paper on the historical differences that may explain what caused the North-South divide over the long-term. We also have an ongoing follow-up set of experiments to try and disentangle the mechanisms driving the differences in cooperation. 

Seminars and workshops



  • Simone Cremaschi ("Journey to the Ghetto. Social mechanisms behind the exploitation of migrant labour")
  • Andris Saulitis ("Pay Up or Else... How people respond to being overindebted")
  • Bernhard Clemm von Hohenberg ("Online Polling Tools and Social Influence")
  • Ezgi Guler ("Do Reactions to Inequality Change as a Function of Social Standing?")
  • Irene Paneda Fernandez ("Migration in Europe: How do the privileged and the underprivileged differ in their conceptions of altruism and fairness?")
  • Melanie Sauter ("Not a target: Violence against humanitarian aid workers")




Selected Publications 


2016: Engineers of Jihad. What education can tell us about violent extremists. Princeton University Press (with Steffen Hertog)

2009: Codes of the underworld. How criminals communicate. Princeton University Press (translated into Chinese and Russian) 

2005: Streetwise. How taxi drivers establish customers’ trustworthiness. New York: Russell Sage Foundation (with Heather Hamill)

1993: The Sicilian mafia. The business of private protection. Harvard University Press (translated into Italian, German, Spanish and Polish)

1987: Were they pushed or did they jump? Individual decision mechanisms in education. Cambridge University Press (translated into Italian)


Edited books:

2005:  Making sense of suicide missions. Oxford: Oxford University Press (translated into Spanish)

1988: Trust. Making and breaking cooperative relations. Oxford: Basil Blackwell (translated into Italian; in a pirated version, in Chinese)



2018. “At the root of the North-South cooperation gap in Italy: Preferences or beliefs?”. The Economic Journal, accepted for publication in February 2018 (with Maria Bigoni, Stefania Bortolotti, and Marco Casari)

2016. “Behind the Veil: the Strategic Use of Religious Garb”. European Sociological Review (with Ozan Aksoy)

2016: "Income and Trustworthiness. Sociological Science" (with John Ermisch)

2015: “Amoral Familism, Social Capital, or Trust? The Behavioural Foundations of the Italian North-South Divide”. The Economic Journal, forthcoming (with Maria Bigoni, Stefania Bortolotti, Marco Casari, and Francesca Pancotto)

2014: “Signs and (counter)signals of trustworthiness”. Journal of Economic Behavior and Organisation, 2014, 106, 281-297 (with Aron Szekely)

2014: “Natural and strategic generosity as a signal of trustworthiness”. PLoS ONE 9(5): e97533. doi:10.1371/journal.pone.0097533 (with Wojtel Przepiorka)

2014: "Thick as thieves: homophily and trust among deviantsRationality and Society, (with Jennifer Flashman)

2013: "It takes two to cheat: an experiment on derived trustEuropean Economic Review, vol. 64, November, pp. 129-146 (with Maria Bigoni, Stefania Bortolotti, Marco Casari)

2012: “The L-worlds. The curious preference for low quality and its norms” Politics, Philosophy and Economics, (with Gloria Origgi), Vol. 12, No. 1, pp. 3-23

2010: “Do strong family ties inhibit trust?” Journal of Economic Behaviour and Organisation, 75, 3, 365-376 (with John Ermisch)

2009: “Why are there so many Engineers among Islamic Radicals?” Archives Européennes de Sociologie, L (2), 201-230 (with Steffen Hertog)

2009: “Heroic impatience": the Baader-Meinhof Gang 1968-1977”, Areté, 29, 11-34 (published in the US in The Nation, 22 March 2010).

2009: “Measuring People’s Trust”, Journal of the Royal Statistical Society, 172 (2009), part 4, 749-769 (with John Ermisch et al.)

2004: “Reason and Terror”, The Boston Review, Spring, 32-36, (published in the UK by Areté, 14, 2004)

1999: “Primo Levi’s last moments”, The Boston Review, summer 1999 (translated into Italian in Belfagor, LIV, 3, 1999 in Spanish in Revista de Occidente, 2004, and in Nuestra Memoria, Fundacion Memoria del Holocausto, 2005) 

1994: “Inscrutable markets”, Rationality and Society, 6, 3, 353-368

1994: “Godfather's gossip”, Archives Européennes de Sociologie, XXXV, 2, 199-223


Chapters in books:

2017. “Why is Italy disproportionally corrupt? A conjecture” in Basu, K. and T. Cordella, eds., Institution, Governance and the Control of Corruption, Palgrave https://www.palgrave.com/de/book/9783319738222

2009: “Signaling”, in P. Hedström and P. Bearman (eds.) The Oxford Handbook of Analytical Sociology, Oxford: Oxford University Press, pp. 168-194

2005: "Deceptive mimicry in humans". In S. Hurley and N. Chater (eds), Perspective or Imitation: From Cognitive Neuroscience to Social Science, Cambridge: MIT Press, vol II pp. 221-241.

2002: “Corruption: An Analytical Map”. In S. Kotkin and A. Sajo (eds.), Political Corruption of Transition: A Sceptic’s Handbook, Budapest: Central European University Press, pp. 33-56

2001: “Trust in signs”. In K. Cook (ed.) Trust and Society, New York: Russell Sage Foundation, pp.148-184 (with Michael Bacharach)

1998: “Claro!’ An essay on discursive machismo”. In J.Elster (ed.), Deliberative Democracy, Cambridge: Cambridge University Press, pp. 19-43

1998: “Concatenations of mechanisms”. In P. Hedström and R. Swedberg (eds.), Social mechanisms. An analytical approach to social theory, Cambridge: Cambridge University Press, pp. 102-24

1995: “Conspiracy among the many: the mafia in legitimate industries” (with Peter Reuter). In G.Fiorentini & S.Peltzman (eds.), The economics of organized crime, Cambridge: Cambridge University Press, pp.116-136

1988: “Can we trust trust?” In Gambetta (ed.) 1988a, 213-234


Page last updated on 23 January 2019