Diego Gambetta

Collegio Carlo Alberto

We provide a conceptual replication of an experimental study that uncovered a robust correlation between the strength of individuals’ family ties and their distrust of strangers, striving to establish whether the link is causal. Using a different subjects pool and an online setting, we repeat the binary trust-game experiment from Ermisch and Gambet...

How does the COVID-19 pandemic affect interpersonal trust? Most evidence shows that natural disasters reinforce trust and cooperation, but the COVID-19 virus differs from other calamities, since it spreads through contact with people, potentially increasing suspicion and distrust, as, according to contemporaneous writers’ accounts, seems to have be...

Religions seem to defy the law-of-demand, which suggests that all else equal, an increase in the cost of an activity will induce individuals to decrease the resources they spend on that activity. Rather than weakening religious organizations, evidence shows that the sacrifices exacted by religious practices are positively associated with the succes...

Does the threat posed by the COVID-19 pandemic affect interpersonal trust? While most evidence shows that natural threats reinforce trust and cooperation, the COVID-19 virus differs from other calamities since it spreads through contact with people, thus potentially increasing mistrust and suspicion towards human beings. We in-vestigate the link be...

Using a natural experiment, we find that in provinces where Turkey’s Islamic Justice and Development Party (AKP) just won the election in 2004, women, including those who are weakly religious or non-religious, now veil far more than in provinces in which AKP just lost, the more so the poorer they are. This effect, as we predict, does not occur for...

Much scientific research shows that the sacrifices imposed by religious practices are positively associated with the success of religious organizations. We present the first evidence that this association is causal. We employ a natural experiment that rests on a peculiar time-shifting feature of Ramadan that makes the length of fasting time vary fr...

Will fights erupt when resources are scarce and the rules regulating their distribution are absent or ignored? We conjecture that the answer depends on whether credible information about individuals’ toughness is available. When people send credible signs and signals of their toughness disputes may be solved without violence. We use a laboratory ex...

Will fights erupt when resources are scarce and the rules regulating their distribution are absent or ignored? We conjecture that the answer depends on whether credible information about individuals’ toughness is available. When people send credible signs and signals of their toughness disputes may be solved without violence. We use a laboratory ex...

Well-enforced norms create an opportunity for norm breakers to cooperate in ventures requiring trust. This is realized when norm breakers, by sharing evidence of their breaches, make themselves vulnerable to denunciation and therefore trustworthy. The sharing of compromising information (SCI) is a strategy employed by criminals, politicians, and ot...

How do political machines decide who should benefit from their patronage and who should not; how do their clients credibly signal their allegiance to the machine? We investigate whether veiling can serve as a signal that helps solve this classic information problem. Exploiting a natural experiment, we find that in provinces where Turkey’s Islamic J...

Different indicators show that Italy is an outlier in terms of corruption. As developed a country as Italy should have a much lower level of corruption. All the factors scholars have found to be affecting corruption fail to explain this puzzle. I start instead from the assumption that corrupt exchanges thrive when parties can trust each other both...

The sharp gap in development between the North and the South of Italy represents a paradigmatic case of persistent within‐country disparities. The evidence suggests that this gap could depend on a difference in the ability to cooperate. We investigate experimentally three possible sources of this difference, and find that Northerners and Southerner...

This article examines signaling theory as an element of analytical sociology, and particularly as an analytic framework for accounting for irrational behaviors. It first provides an overview of the basic principles of signaling theory, focusing on the distinction between signs and signals as well as the concepts of differential costs and differenti...

We employ a behavioral measure of trustworthiness obtained from a trust game carried out with a sample of the general British population, the individuals of which were extensively interviewed on earlier occasions. Our basic finding is that given past income, higher current income increases trustworthiness and, given current income, higher past inco...

There is anecdotal evidence that since the late 20th century young, educated, and urban Muslim women veil more frequently and strictly. Does this imply that the classical sociological theories of religion, which predict that modernization should cause a decrease in religious behaviours, do not apply to Islam? We investigate this question using stru...

The violent actions of a few extremists can alter the course of history, yet there persists a yawning gap between the potential impact of these individuals and what we understand about them. In Engineers of Jihad, Diego Gambetta and Steffen Hertog uncover two unexpected facts, which they imaginatively leverage to narrow that gap: they find that a d...

We present the first lab-in-the field experiment on the Italian North-South divide. Using a representative sample of the population, we measure whether regional disparities in ability to cooperate emerge even if differences in geography, institutions, and criminal intrusion are silenced. We report that a behavioural gap in cooperation exists: North...

This volume advances the research agenda of one of the most remarkable political thinkers of our time: Jon Elster. With an impressive list of contributors, it features studies in five topics in political and social theory: rationality and collective action, political and social norms, democracy and constitution making, transitional justice, and the...

When we become aware that our past actions carry information about qualities that we possess or lack, which others use to decide how to deal with us, are we unconcerned, content to rely on what we have done, or do we take action to alter this information? We study this question experimentally using generosity as a sign and a signal of trustworthine...

We exploit the fact that generosity and trustworthiness are highly correlated and the former can thus be a sign of the latter. Subjects decide between a generous and a mean split in a dictator game. Some of them are informed from the start that afterwards they will participate in a trust game and that their choice in the dictator game may matter; o...

Individuals who engage in deviant behaviors are more likely to be friends with other deviants compared to non-deviants. This pattern has been observed across different types of deviant activities and among different age groups. In question, however, is the mechanism that underlies this pattern. In this article we develop and test a new theory to ex...

Socio-economic performance differs not only across countries but within countries too and can persist even after religion, language, and formal institutions are long shared. One interpretation of these disparities is that successful regions are characterized by higher levels of trust, and, more generally, of cooperation. Here we study a classic cas...

We investigate a phenomenon which we have experienced as common when dealing with an assortment of Italian public and private institutions: people promise to exchange high quality goods and services (H), but then something goes wrong and the quality delivered is lower than promised (L). While this is perceived as ‘cheating' by outsiders, insiders s...

Social life offers innumerable instances in which trust relations involve multiple agents. In an experiment, we study a new setting called Collective Trust Game where there are multiple trustees, who may have an incentive to coordinate their actions. Trustworthiness has also a strategic motivation, and the trusters' decision depends upon their beli...

How do criminals communicate with each other? Unlike the rest of us, people planning crimes can't freely advertise their goods and services, nor can they rely on formal institutions to settle disputes and certify quality. They face uniquely intense dilemmas as they grapple with the basic problems of whom to trust, how to make themselves trusted, an...

We employ a behavioural measure of trustworthiness obtained from an experiment carried out with a sample of the general British population whose individuals were extensively interviewed on earlier occasions. These previous interviews allow us to have very good income measures, and in particular to construct a measure of relative income that uses pa...

We measure trust and trustworthiness in British society with a newly designed experiment using real monetary rewards and a sample of the British population. The study also asks the typical survey question that aims to measure trust, showing that it does not predict 'trust' as measured in the experiment. Overall, about 40% of people were willing to...

This article demonstrates that among violent Islamists engineers with a degree, individuals with an engineering education are three to four times more frequent than we would expect given the share of engineers among university students in Islamic countries.We then test a number of hypotheses to account for this phenomenon.We argue that a combinatio...

Predicting who will become a terrorist is a tough job, but we're beginning to get good clues from what people study

My course, which comprised 4 lectures, was an introduction to the principles of signalling theory, its history, and its common misconceptions. I also presented two applications: to trust decisions and to interpersonal violence. Herewith, I give a brief overview of the theory and of the range of its applications, without going into the details of th...

We provide direct evidence that people with strong family ties have a lower level of trust in strangers than people with weak family ties, and argue that this association is causal. We also investigate the mechanisms that underlie this effect, and provide evidence that these revolve around the level of outward exposure: factors that limit exposure...

This book attempts to shed light on suicide missions and provide answers to the questions we all ask. Are these the actions of aggressive religious zealots and unbridled, irrational radicals or is there a logic driving those behind them? Are their motivations religious or has Islam provided a language to express essentially political causes? How ca...

We find that graduates from subjects such as science, engineering, and medicine are strongly overrepresented among Islamist movements in the Muslim world, though not among the extremist Islamic groups which have emerged in Western countries more recently. We also find that engineers alone are strongly over-represented among graduates in violent gro...

Driving a taxi is dangerous, and picking up the wrong fare can be devastating. Yet drivers only have a moment to make a choice.

In this paper we present the design of a two-stage experiment which aims to measure trusting and trustworthiness in a representative sample of the British population. In the first part we discuss the shortcomings of the most common design of the ‘trust-game’ experiment in eliciting information about clear and cogent notions of trusting and trustwor...

This chapter begins by reviewing the variety and uniformity of features found in suicide missions (SMs) and among their organizers. It then reviews what is known about the perpetrators, arguing that the persons who die in SMs and the conditions that promote their self-sacrifice are fairly uniform, and although they are rare they are not historicall...

A taxi driver's life is dangerous work. Picking up a bad customer can leave the driver in a vulnerable position, and erring even once can prove fatal. To protect themselves, taxi drivers must quickly and accurately assess the trustworthiness of complete strangers. In Streetwise, Diego Gambetta and Heather Hamill take this predicament as a prototypi...

The system of proportional representation by which all Italian governments have been elected since the ratification of the present constitution dates from 1946. It predated the constitution itself and was never included in that document, so the reform of the electoral system requires no constitutional amendment. There were some minor alterations in...

In this article we embark on a re-orientation of the theory of trust which contains three steps1.

whether we necessarily need more cooperation, keeping, for the moment, the distinction between cooperation and trust blurred and their relationship implicit. According to the trite observation - Adam Smith wrote - if there is any society among robbers and murderers, they must at least abstain from robbing and murdering one another (Smith [1759] 197...

this paper is to reconcile individual rationality with protracted collective disaster. If anything, in this case, the latter results from an excess of individual rationality. This paper is an account of the remarkable responses to a generalized absence of trust and of the mechanisms by which such responses, while reinforcing distrust, have none the...

influence, the conditions which induce the entry of the mafia in specific industries, and the conditions and policies which make it disappear. The authors share the view that mafia protection in legitimate industries, although occasionally rapacious and unreliable, is frequently neither bogus nor limited to intimidating new entrants. Under some (pe...

It is sometimes assumed that voting is the central mechanism for political decision-making. The contributors to this volume focus on an alternative mechanism, that is decision by discussion or deliberation. The original contributions include case studies based on historical and current instances of deliberative democracy, normative discussion of th...

The advancement of social theory requires an analytical approach that systematically seeks to explicate the social mechanisms that generate and explain observed associations between events. These essays, written by prominent social scientists, advance criticisms of current trends in social theory and suggest alternative approaches. The mechanism ap...

The article assesses the effects, direct and indirect, intended and unintended, of the 1993 national electoral reform and the results of the 1994 general elections in Italy. It shows that the new system is not an eccentric compromise, and that those who forecast either its unworkability or its evil consequences were mistaken. However, in evaluating...

This is the first book to use economic theory in the analysis of all the different aspects of organised crime: the origins, the internal organisation, market behaviour and deterrence policies. The theory of rent-seeking is adopted to help understand the origin of criminal organisations from a state of anarchy, while modern industrial organisation t...

This chapter considers the modes by which the mafia exercises its influence on a number of legitimate industries in both Sicily and the United States. In particular it discusses the kinds of service the mafia provides, the economic consequences of its influence, the conditions that induce the entry of the mafia in specific industries, and the condi...

My attention to gossip as a notion worthy of reflection was attracted by a trivial detail: the English etymology of gossip is god-sib , godfather, or, generally, god parent, ‘denoting—says the English Oxford Dictionary—the spiritual affinity of the baptized and their sponsor’. This intriguing origin alludes to gossip as the performing of an initiat...

Unlike markets that are subject to asymmetric information, in inscrutable markets-such as religions and psychotherapies-not just buyers but sellers too do not know much about the quality of their products. Because buyers cannot discern which products are of good quality and sellers cannot construct ''honest'' signals to guide them, rational choice...

Most expressions and symbols associated with the mafia—indeed, the term mafia itself—are made up of an almost surrealist cocktail of bogus and genuine sources, mythical and prosaic characters, fiction and reality. Already in 1876, Franchetti was puzzling over ‘the tendency to turn a mafioso into a legendary type, a feeling natural enough indeed in...

We know much and understand little about the Italian mafia. The amount of factual information surrounding it—whatever that ‘it’ may be—is disproportionately and dramatically greater than our theoretical understanding of this elusive entity. We do not know everything it might be interesting to know, of course, yet in the monumental quantity of schol...

This book explores the factors which govern the range of educational decisions confronting individuals between compulsory school education and university. The data on which it draws come from two surveys conducted in north-west Italy, one of unemployed young people and one of high-school pupils. The author is in effect testing the two fundamental a...

Examined some of the mechanisms of educational choice in Italy through an analysis of 2 surveys conducted in the Piedmont region of Italy. Data were obtained from 1,031 high school students in one survey and from 1,739 14–29 yr olds who were not in school in the other. It is concluded that educational decisions in Italy can be characterized as an i...

This article demonstrates that among violent Islamists engineers with a degree, individuals with an engineering education are three to four times more frequent than we would expect given the share of engineers among university students in Islamic countries. We then test a number of hypotheses to account for this phenomenon. We argue that a combinat...

Traducción de: The Sicilian Mafia. The Business of Private Protection La tesis del autor de esta obra es que la mafia siciliana apareció porque esta organización tomó la falta de protección que el estado no proveía para garantizar las transacciones comerciales por medio de la venta de protección. Por otro lado esta comunidad criminal no es una orga...