Valerio Capraro

Università degli Studi di Milano-Bicocca | UNIMIB · Department of Psychology

Are humans intuitively altruistic, or does altruism require self-control? A theory of social heuristics, whereby intuitive responses favor typically successful behaviors, suggests that the answer may depend on who you are. In particular, evidence suggests that women are expected to behave altruistically, and are punished for failing to be altruisti...

The opportunity to tell a white lie (i.e., a lie that benefits another person) generates a moral conflict between two opposite moral dictates, one pushing towards telling always the truth and the other pushing towards helping others. Here we study how people resolve this moral conflict. What does telling a white lie signal about a person's pro-soci...

Cooperation in one-shot anonymous interactions is a widely documented aspect of human behaviour. Here we shed light on the motivations behind this behaviour by experimentally exploring cooperation in a one-shot continuous-strategy Prisoner’s Dilemma (i.e. one-shot two-player Public Goods Game). We examine the distribution of cooperation amounts, an...

Sofic and hyperlinear groups are the countable discrete groups that can be approximated in a suitable sense by finite symmetric groups and groups of unitary matrices. These notions turned out to be very deep and fruitful, and stimulated in the last 15 years an impressive amount of research touching several seemingly distant areas of mathematics inc...

SOCIAL DILEMMAS ARE SITUATIONS IN WHICH COLLECTIVE INTERESTS ARE AT ODDS WITH PRIVATE INTERESTS: pollution, depletion of natural resources, and intergroup conflicts, are at their core social dilemmas. Because of their multidisciplinarity and their importance, social dilemmas have been studied by economists, biologists, psychologists, sociologists,...

Generative artificial intelligence holds enormous potential to revolutionize decision-making processes, from everyday to high-stake scenarios. However, as many decisions carry social implications, for AI to be a reliable assistant for decision-making it is crucial that it is able to capture the balance between self-interest and the interest of othe...

Understanding what factors are linked to public health behavior in a global pandemic is critical to mobilizing an effective public health response. Although public policy and health messages are often framed through the lens of individual benefit, many of the behavioral strategies needed to combat a pandemic require individual sacrifices to benefit...

The COVID-19 pandemic has affected all domains of human life, including the economic and social fabric of societies. One of the central strategies for managing public health throughout the pandemic has been through persuasive messaging and collective behaviour change. To help scholars better understand the social and moral psychology behind public...

Professional fact-checking of individual news headlines is an effective way to fight misinformation, but it is not easily scalable, because it cannot keep pace with the massive speed at which news content gets posted on social media. Here we provide evidence for the effectiveness of ratings of news sources, instead of individual news articles. In a...

In a world severely put under stress by COVID-19, generosity becomes increasingly essential both when able to transcend local boundaries, building upon universalistic values, and when directed toward more local contexts, such as the native country. This study aims to investigate an underresearched determinant of generosity at these two levels, a fa...

In this paper we investigate the effect of moral suasion on ingroup favouritism. We report a well-powered, pre-registered, two-stage 2x2 mixed-design experiment. In the first stage, groups are formed on the basis of how participants answer a set of questions, concerning non-morally relevant issues in one treatment (assorting on non-moral preference...

We report on three pre-registered studies testing whether people in the position of describing a decision problem to decision-makers exploit this opportunity for their benefit, by choosing descriptions that may be potentially beneficial for themselves. In Study 1, recipients of an extreme dictator game (where dictators can either take the whole pie...

Understanding whether preferences are sensitive to the frame has been a major topic of debate in the last decades. For example, several works have explored whether the dictator game in the give frame gives rise to a different rate of pro-sociality than the same game in the take frame, leading to mixed results. Here we contribute to this debate with...

Social and behavioral science research proliferated during the COVID-19 pandemic, reflecting the substantial increase in influence of behavioral science in public health and public policy more broadly. This review presents a comprehensive assessment of 742 scientific articles on human behavior during COVID-19. Two independent teams evaluated 19 sub...

Accuracy prompts, nudges that make accuracy salient, typically decrease the sharing of fake news, while having little effect on real news. Here, we introduce a new accuracy prompt that is more effective than previous prompts, because it does not only reduce fake news sharing, but it also increases real news sharing. We report four preregistered stu...

At the beginning of 2020, COVID-19 became a global problem. Despite all the efforts to emphasize the relevance of preventive measures, not everyone adhered to them. Thus, learning more about the characteristics determining attitudinal and behavioral responses to the pandemic is crucial to improving future interventions. In this study, we applied ma...

We review the literature on models that try to explain human behavior in social interactions described by normal-form games with monetary payoffs. We start by covering social and moral preferences. We then focus on the growing body of research showing that people react to the language in which actions are described, especially when it activates mor...

We review the literature on models that try to explain human behavior in social interactions described by normal-form games with monetary payoffs. We start by covering social and moral preferences. We then focus on the growing body of research showing that people react to the language in which actions are described, especially when it activates mor...

Changing collective behaviour and supporting non-pharmaceutical interventions is an important component in mitigating virus transmission during a pandemic. In a large international collaboration (Study 1, N = 49,968 across 67 countries), we investigated self-reported factors associated with public health behaviours (e.g., spatial distancing and str...

Previous studies have shown that women tend to be more egalitarian and less self-interested than men whereas men tend to be more concerned with social efficiency motives. The roots of such differences, however, remain unknown. Since different cognitive styles have also been associated with different distributional social preferences, we hypothesise...

Sender-receiver games are simple models of information transmission that provide a formalism to study the evolution of honest signaling and deception between a sender and a receiver. In many practical scenarios, lies often affect groups of receivers, which inevitably entangles the payoffs of individuals to the payoffs of other agents in their group...

Sender-receiver games are simple models of information transmission that provide a formalism to study the evolution of honest signaling and deception between a sender and a receiver. In many practical scenarios, lies often affect groups of receivers, which inevitably entangles the payoffs of individuals to the payoffs of other agents in their group...

Do people discriminate between men and women when they have the option to punish defectors or reward cooperators? Here, we report on four pre-registered experiments that shed some light on this question. Study 1 (N = 544) shows that people do not discriminate between genders when they have the option to punish (reward) defectors (cooperators) in a...

In this article, we study whether people in the position of describing a decision problem to decision-makers exploit this opportunity for their benefit, by choosing descriptions that may be potentially beneficial for themselves. To this end, we design, pre-register, and conduct an experiment in which dictator game recipients are asked to choose the...

Cooperation is essential to overcome global pandemics and other health crises, as many preventative measures require people to bear a personal cost to benefit other people or society as a whole. Wearing a face mask, for example, protects other people more than it protects oneself. In this essay, we discuss several mechanisms that are known to promo...

A growing body of work suggests that people are sensitive to moral framing in economic games involving prosociality, suggesting that people hold moral preferences for doing the “right thing”. What gives rise to these preferences? Here, we evaluate the explanatory power of a reputation-based account, which proposes that people respond to moral frame...

One-shot anonymous unselfishness in economic games is commonly explained by social preferences, which assume that people care about the monetary pay-offs of others. However, during the last 10 years, research has shown that different types of unselfish behaviour, including cooperation, altruism, truth-telling, altruistic punishment and trustworthin...

Finding messaging to promote the use of face masks is fundamental during a pandemic. Study 1 (N=399) shows that telling people to “rely on their reasoning” increases intentions to wear a face mask, compared with telling them to “rely on their emotions”. In Study 2 (N=591) we add a baseline. However, the results show only a non‐significant trend. St...

One-shot anonymous unselfishness in economic games is commonly explained by social preferences, which assume that people care about the monetary payoffs of others. However, during the last ten years, research has shown that different types of unselfish behaviour, including cooperation, altruism, truth-telling, altruistic punishment, and trustworthi...

We report three pre-registered studies (total N=1,799) exploring the effect of nudging personal and injunctive norms in decisions that involve a trade-off between objective equality and efficiency. The first two studies provide evidence that: (i) nudging the personal norm has a similar effect to nudging the injunctive norm; (ii) when both norms are...

We report three pre-registered studies (total N=1,799) exploring the effect of nudging personal and injunctive norms in decisions that involve a trade-off between objective equality and efficiency. The first two studies provide evidence that: (i) nudging the personal norm has a similar effect to nudging the injunctive norm; (ii) when both norms are...

The ongoing COVID-19 pandemic is a devastating global health crisis. Without a vaccine or effective medication, the best hope for mitigating virus transmission is collective behavior change and support for public health interventions (e.g., physical distancing, physical hygiene, and endorsement of health policies). In a large-scale international co...

Trust and trustworthiness form the basis for continued social and economic interactions, and they are also fundamental for cooperation, fairness, honesty, and indeed for many other forms of prosocial and moral behavior. However, trust entails risks, and building a trustworthy reputation requires effort. So how did trust and trustworthiness evolve,...

Trust and trustworthiness form the basis for continued social and economic interactions, and they are also fundamental for cooperation, fairness, honesty, and indeed for many other forms of prosocial and moral behaviour. However, trust entails risks, and building a trustworthy reputation requires effort. So how did trust and trustworthiness evolve,...

Finding mechanisms to promote the use of face masks is fundamental during the second phase of the COVID-19 pandemic response, when shelter-in-place rules are relaxed and some segments of the population are allowed to circulate more freely. Here we report three pre-registered studies (total N = 1,920), using an heterogenous sample of people living i...

Now that various countries are or will soon be moving towards relaxing shelter-in-place rules, it is important that people use a face covering, to avoid an exponential resurgence of the spreading of the coronavirus disease (COVID-19). Here we report a pre-registered online experiment (N=2,459) using a heterogenous, although not representative, samp...

The new coronavirus disease (COVID-19) threatens the lives of millions of people around the world, making it the largest health threat in recent times. Billions of people around the world are asked to adhere to strict shelter-in-place rules, finalised to slow down the spread of the virus. Appeals and messages are being used by leaders and policy-ma...

The COVID-19 pandemic represents a massive global health crisis. Because the crisis requires large-scale behaviour change and places significant psychological burdens on individuals, insights from the social and behavioural sciences can be used to help align human behaviour with the recommendations of epidemiologists and public health experts. Here...

A growing body of work suggests that people are sensitive to moral framing in economic games involving prosociality, suggesting that people hold moral preferences for doing the "right thing". What gives rise to these preferences? Here, we evaluate the explanatory power of a reputation-based account, which proposes that people respond to moral frame...

Do people discriminate between men and women when they are in charge of punishing defectors or rewarding cooperators? Answering this question has potentially far-reaching implications on gender equity, since cooperative behaviour forms the basis of our societies and is typically enforced through punishment or rewarding. In this paper we report on t...

The COVID-19 pandemic represents a massive, global health crisis. Because the crisis requires large-scale behavior change and poses significant psychological burdens on individuals, insights from the social and behavioural sciences are critical for optimizing pandemic response. Here we review relevant research from a diversity of research areas rel...

Lies can have a negating impact on governments, companies, and the society as a whole. Understanding the dynamics of lying is therefore of crucial importance across different fields of research. While lying has been studied before in well-mixed populations, it is a fact that real interactions are rarely well-mixed. Indeed, they are usually structur...

Recent work highlights that cooperation in the one-shot Prisoner's dilemma (PD) is primarily driven by moral preferences for doing the right thing, rather than social preferences for equity or efficiency. To our knowledge, nothing is known on whether moral preferences affect cooperation in the Stag-Hunt Game (SHG). Cooperation in the SHG fundamenta...

In this paper we investigate the effect of moral suasion on ingroup favouritism. We report a well-powered, pre-registered, two-stage 2x2 mixed-design experiment. In the first stage, groups are formed on the basis of how participants answer to a set of questions, concerning non-morally relevant issues in one treatment (assorting on non-moral prefere...

Lies can have a negating impact on governments, companies, and the society as a whole. Understanding the dynamics of lying is therefore of crucial importance across different fields of research. While lying has been studied before in well-mixed populations, it is a fact that real interactions are rarely well-mixed. Indeed, they are usually structur...

We explore whether priming emotion versus deliberation affects speciesism—the tendency to prioritize certain individuals over others on the basis of their species membership (three main and two supplementary studies, four preregistered; N = 3,288). We find that the tendency to prioritize humans over animals (anthropocentric speciesism) decreases wh...

[This corrects the article DOI: 10.1371/journal.pone.0205066.].

In this paper we investigate the effect of moral suasion on ingroup favouritism. We report a well-powered, pre-registered, two-stage 2x2 mixed-design experiment. In the first stage, groups are formed on the basis of how participants answer to a set of questions, concerning non-morally relevant issues in one treatment (assortativity on non-moral pre...

Understanding the cognitive underpinnings of moral judgment is one of most pressing problems in psychological science. Some highly-cited studies suggest that reliance on intuition decreases utilitarian (expected welfare maximizing) judgments in sacrificial moral dilemmas in which one has to decide whether to instrumentally harm (IH) one person to s...

In the past few decades, numerous experiments have shown that humans do not always behave so as to maximize their material payoff. Cooperative behavior when noncooperation is a dominant strategy (with respect to the material payoffs) is particularly puzzling. Here we propose a novel approach to explain cooperation, assuming what Halpern and Pass ca...

We explore whether priming emotion versus deliberation affects speciesism—the tendency to prioritize certain individuals over others on the basis of their species-membership (three main and two supplementary studies; four pre-registered; N = 3,288). We find that the tendency to prioritize humans over animals (anthropocentric speciesism) decreases w...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The conflict between pro-self and pro-social behaviour is at the core of many key problems of our time, as, for example, the reduction of air pollution and the redistribution of scarce resources. For the well-being of our societies, it is thus crucial to find mechanisms to promote pro-social choices over egoistic ones. Particularly important, becau...

This paper studies lying in a novel context. Previous work has focused on situations in which people are either fully aware of the economic consequences of all available actions (e.g., die-under-cup paradigm), or they are uncertain, but this uncertainty cannot be cleared in any way (e.g., sender-receiver game). On the contrary, in reality, people o...

Recent work highlights that cooperation in the one-shot Prisoner's dilemma (PD) is primarily driven by moral preferences for doing the right thing, rather than social preferences for equity or efficiency. By contrast, little is known on what motivates cooperation in the Stag-Hunt Game (SHG). Cooperation in the SHG fundamentally differs from coopera...

Lies can have profoundly negative consequences for individuals, groups and even for societies. Understanding how lying evolves and when it proliferates is therefore of significant importance for our personal and societal well-being. To that effect, we here study the sender-receiver game in well-mixed populations with methods of statistical physics....

Lies can have profoundly negative consequences for individuals, groups, and even for societies. Understanding how lying evolves and when it proliferates is therefore of significant importance for our personal and societal well-being. To that effect, we here study the sender-receiver game in well-mixed populations with methods of statistical physics...

We experimentally study how redistribution choices are affected by positive and negative information regarding the behaviour of a previous participant in a dictator game with a taking option. We use the strategy method to identify behavioural "types", and thus distinguish "conformists" from "counter-conformists", and unconditional choosers. Uncondi...

The conflict between pro-self and pro-social behaviour is at the core of many key problems of our time, as, for example, the reduction of air pollution and the redistribution of scarce resources. For the well-being of our societies, it is thus crucial to find mechanisms to promote pro-social choices over egoistic ones. Particularly important, becau...

We experimentally study how redistribution choices are affected by positive and negative information regarding the behaviour of a previous participant in a dictator game with a taking option. We use the strategy method to identify behavioural ‘types’, and thus distinguish ‘conformists’ from ‘counter-conformists’, and unconditional choosers. Uncondi...

Which social decisions are intuitive? Which are deliberative? The dual-process approach to human sociality has emerged in the last decades as a vibrant and exciting area of research. Here, I review the existing literature on the cognitive basis of cooperation, altruism, honesty, equity-efficiency, positive and negative reciprocity, and moral judgme...

Which social decisions are intuitive? Which are deliberative? The dual-process approach to human sociality has emerged in the last decades as a vibrant and exciting area of research. Here, I review the existing literature on the cognitive basis of cooperation, altruism, honesty, equity-efficiency, positive and negative reciprocity, and moral judgme...

In this paper we investigate the evolution of cooperation when the interaction structure is strictly local, and hence fitness only depends on local behaviors, while the competition structure is partly global, and hence selection can happen also between distant agents. We explore this novel setup by means of numerical simulations in a model where ag...

Understanding the cognitive underpinnings of moral judgment is one of most pressing problems in psychological science. Some highly-cited studies suggest that reliance on intuition decreases utilitarian (expected welfare maximizing) judgments in sacrificial moral dilemmas in which one has to decide whether to instrumentally harm (IH) one person to s...

Gender differences in human behaviour have attracted generations of social scientists, who have explored whether males and females act differently in domains involving competition, risk taking, cooperation, altruism, honesty, as well as many others. Yet, little is known about gender differences in the equity-efficiency trade-off. This gap is partic...

Understanding whether the size of the interacting group has an effect on cooperative behavior has been a major topic of debate since the seminal works on cooperation in the 1960s. Half a century later, scholars have yet to reach a consensus, with some arguing that cooperation is harder in larger groups, while others that cooperation is easier in la...

Previous experiments have found mixed results on whether honesty is intuitive or requires deliberation. Here we add to this literature by building on prior work of Capraro (2017). We report a large study (N = 1,389) manipulating time pressure vs time delay in a deception game. We find that, in this setting, people are more honest under time pressur...

Understanding the cognitive underpinnings of moral judgment is one of most pressing problems in psychological science. Classic studies suggest that intuition decreases utilitarian (expected welfare maximizing) judgments in sacrificial moral dilemmas, in which one has to decide whether to instrumentally harm (IH) one person to save a greater number...

Recent work shows that people are not solely motivated by the economic consequences of the available actions, but they also have moral preferences for `doing the right thing', independently of its economic consequences. Here we add to this literature with two experiments. In Study 1 ($N=567$) we implement an extreme dictator game in which dictators...