We elicit and compare behaviors in the laboratory and on a smartphone application that we developed for this study. Our participant pool consists of university students who are subjected to identical incentives and selection criteria. Behavior is similar across samples in measures of attitudes towards risk, effort, cognitive ability, strategic reasoning, trust, and lying aversion. Additionally, participants show comparable beliefs about the actions of the other players. We also identify certain quantitative differences between the two groups. Specifically, subjects using the app donate more in the dictator game, are faster, and show less consistency. These findings show the potential of using smartphone applications to organize experiments and emphasize the importance of a clear and simple interface in this environment.

Using an app for smartphones, we run an experiment among high-school students to study the pattern of aggregation of sparsely distributed information. Agents are randomly arranged in small networks and can share only non-verifiable pieces of information. Results show that while information exchange is high, the level and the distribution of centralities among network members are important to shape the overall level of information aggregation. A reduction in the asymmetry among agents’ network centralities is associated with an improvement in the performance of the group in terms of aggregation of information.

We study how the spread of the Lost Cause narrative—a revisionist and racist retelling of the US Civil War—shifted opinions and behaviors toward national reunification and racial discrimination against African Americans. Looking at screenings of The Birth of a Nation, a blockbuster movie that greatly popularized the Lost Cause after 1915, we find that the film shifted the public discourse toward a more patriotic and less divisive language, increased military enlistment, and fostered cultural convergence between former enemies. We document how the racist content of the narrative connects to reconciliation through a "common-enemy" type of argument.

Parental hesitancy poses a serious threat to the success of the COVID-19 childhood vaccination campaign. We investigate whether adults' opinions on childhood vaccination can be influenced via two survey experiments in Italy (n= 3,633 participants) and the UK (n= 3,314 participants). Respondents were randomly assigned to: a “risk treatment” that highlighted the potential risks of COVID-19 to a child, a “herd immunity treatment” that emphasized the community benefits of pediatric vaccination, or a control message. Participants’ probability of supporting COVID-19 childhood vaccination was then assessed on a 0-100 scale. We find that the “risk treatment” reduced the proportion of Italian parents strongly against vaccination by up to 29.6%, while increasing the proportion of neutral parents by up to 45.0%. The “herd immunity treatment”, instead, was only effective among non-parents, resulting in a lower proportion of individuals against pediatric vaccination and a higher proportion of individuals in favor (both shifted by around 20%).

As immunization campaigns are accelerating, understanding how to distribute the scarce doses of vaccines is of paramount importance and a quantitative analysis of the trade-offs involved in domestic-only versus cooperative distribution is still missing. In this study we use a network Susceptible-Infected-Removed (SIR) model to show circumstances under which it is in a country’s self-interest to ensure other countries can obtain COVID-19 vaccines rather than focusing only on vaccination of their own residents. In particular, we focus our analysis on the United States and estimate the internal burden of COVID-19 disease under different scenarios about vaccine cooperation. We show that in scenarios in which the US has reached the threshold for domestic herd immunity, the US may find it optimal to donate doses to other countries with lower vaccination coverage, as this would allow for a sharp reduction in the inflow of infected individuals from abroad.

In the absence of widespread vaccination for COVID-19, governments and public health officials have advocated for the public to wear masks during the pandemic. The decision to wear a mask in public is likely affected by both beliefs about its efficacy and the prevalence of the behavior. Greater mask use in the community may encourage others to follow this norm, but it also creates an incentive for individuals to free ride on the protection afforded to them by others. We report the results of two vignette-based experiments conducted in the United States (n = 3,100) and Italy (n = 2,659) to examine the causal relationship between beliefs, social norms, and reported intentions to engage in mask promoting behavior. In both countries, survey respondents were quota sampled to be representative of the country’s population on key demographics. We find that providing information about how masks protect others increases the likelihood that someone would wear a mask or encourage others to do so in the United States, but not in Italy. There is no effect of providing information about how masks protect the wearer in either country. Additionally, greater mask use increases intentions to wear a mask and encourage someone else to wear theirs properly in both the United States and Italy. Thus, community mask use may be self-reinforcing.

What is the effect of Twitter on political participation? I study how the spread of this social network has affected voting behavior and donations to politicians during the 2008, 2012, and 2016 US presidential elections. To do this, I develop a novel measure of Twitter penetration using location data collected from users. To address endogeneity in the diffusion of Twitter across regions, I exploit variation in the popularity of sport teams that have signed new players with Twitter accounts, thus making the social network more interesting for their fans. My instrumental variables estimates do not show significant effects of Twitter on average participation, as measured by turnout and donations to politicians. However, I find a differential effect across parties, with the Democratic Party being penalized in terms of votes and the Republican Party receiving more donations. I provide two pieces of evidence on the mechanisms behind these results. First, I show that Twitter reduces voters' information about politics and increases political polarization. Second, by downloading and categorizing tweets written by users, I show that the majority of users write about sports or entertainment and ignore politics for most of the year. Peaks in interest happen only during presidential debates, when both the quantity of partisan tweets and the average sentiment favor the Republican Party.