Post-January 6th deplatforming reduced the reach of misinformation on Twitter.

The social media platforms of the twenty-first century have an enormous role in regulating speech in the USA and worldwide1. However, there has been little research on platform-wide interventions on speech2,3. Here we evaluate the effect of the decision by Twitter to suddenly deplatform 70,000 misinformation traffickers in response to the violence at the US Capitol on 6 January 2021 (a series of events commonly known as and referred to here as 'January 6th'). Using a panel of more than 500,000 active Twitter users4,5 and natural experimental designs6,7, we evaluate the effects of this intervention on the circulation of misinformation on Twitter. We show that the intervention reduced circulation of misinformation by the deplatformed users as well as by those who followed the deplatformed users, though we cannot identify the magnitude of the causal estimates owing to the co-occurrence of the deplatforming intervention with the events surrounding January 6th. We also find that many of the misinformation traffickers who were not deplatformed left Twitter following the intervention. The results inform the historical record surrounding the insurrection, a momentous event in US history, and indicate the capacity of social media platforms to control the circulation of misinformation, and more generally to regulate public discourse.

Mental health concerns during the COVID-19 pandemic as revealed by helpline calls.

Mental health is an important component of public health, especially in times of crisis. However, monitoring public mental health is difficult because data are often patchy and low-frequency1-3. Here we complement established approaches by using data from helplines, which offer a real-time measure of 'revealed' distress and mental health concerns across a range of topics4-9. We collected data on 8 million calls from 19 countries, focusing on the COVID-19 crisis. Call volumes peaked six weeks after the initial outbreak, at 35% above pre-pandemic levels. The increase was driven mainly by fear (including fear of infection), loneliness and, later in the pandemic, concerns about physical health. Relationship issues, economic problems, violence and suicidal ideation, however, were less prevalent than before the pandemic. This pattern was apparent both during the first wave and during subsequent COVID-19 waves. Issues linked directly to the pandemic therefore seem to have replaced rather than exacerbated underlying anxieties. Conditional on infection rates, suicide-related calls increased when containment policies became more stringent and decreased when income support was extended. This implies that financial relief can allay the distress triggered by lockdown measures and illustrates the insights that can be gleaned from the statistical analysis of helpline data.

Political organization and gender predict violence in the Andean archaeological record.

The relationship between sociopolitical organization and violence remains an enduring question in anthropological research. Less studied is the articulation of gender with violence in societies of different sociopolitical organization. We investigate the frequency and type of violence experienced by adult males and females in pre-Hispanic Andean archaeological contexts, comparing exposure to antemortem (nonlethal) and perimortem (potentially lethal) violence across three categories of sociopolitical organization: autonomous communities, regional cultural formations, and states. Using a database of 8,607 adults from 169 publications and over 155 sites, we construct a multinomial logistic regression using Bayesian Hamiltonian Monte Carlo methods to fit our model. The odds of antemortem and perimortem trauma were low for both sexes. However, the odds of antemortem trauma were consistently higher for males than females in all categories of sociopolitical organization, suggesting that men were more frequently exposed to violence. Males display similar odds of cranial trauma across all forms of sociopolitical organization, while females display slightly reduced odds of cranial trauma in states compared to autonomous communities. Perimortem trauma is especially strongly patterned by sex. In autonomous communities, the odds of potentially lethal cranial trauma are equivalent between the sexes; in states, they are consistent for males, but depressed for females. In the pre-Hispanic Andes, living in states dramatically reduced the chances of encountering lethal violence for females, but not males. Our study complicates the notion that increasing sociopolitical complexity leads to decreasing interpersonal violence and highlights the importance of gender in understanding the human history of violence.

Understanding the relationship between intergenerational mobility and community violence.

Violence is a key mechanism in the reproduction of community disadvantage. The existing evidence indicates that violence in a community impacts the intergenerational mobility of its residents. The current study explores the possibility of a reverse relationship. This study provisionally tests the hypothesis that depressed intergenerational mobility in a community may also spark subsequent community violence. We deploy a county measure of intergenerational mobility captured during early adulthood for a cohort of youth born between 1980 and 1986 and raised in low-income families [R. Chetty, N. Hendren, Quart. J. Econom. 133, 1163-1228 (2018)]. We model the relationship between county mobility scores and two county-level outcomes: violent crime and homicide. We find that a county's level of intergenerational mobility as measured by the Chetty-Hendren data is a major predictor of its rate of violent crime and homicide in 2008, when the youth in Chetty's mobility cohort were young adults (the same age the mobility measure was captured). In fact, mobility is a significantly stronger and more consistent predictor of community violent crime and homicide rates than more commonly used factors like poverty, inequality, unemployment, and law enforcement presence.

The politics of allyship: Multiethnic coalitions and mass attitudes toward protest.

Recent work finds that nonviolent resistance by ethnic minorities is perceived as more violent and requiring more policing than identical resistance by ethnic majorities, reducing its impact and effectiveness. We ask whether allies-advantaged group participants in disadvantaged group movements-can mitigate these barriers. On the one hand, allies can counter negative stereotypes and defuse threat perceptions among advantaged group members, while raising expectations of success and lowering expected risks among disadvantaged group members. On the other hand, allies can entail significant costs, carrying risks of cooptation, replication of power hierarchies, and marginalization of core constituencies. To shed light on this question we draw on the case of the Black Lives Matter (BLM) movement, which, in 2020, attracted unprecedented White participation. Employing a national survey experiment, we find that sizeable White presence at racial justice protests increases protest approval, reduces perceptions of violence, and raises the likelihood of participation among White audiences, while not causing significant backlash among Black audiences. Black respondents mostly see White presence as useful for advancing the movement's goals, and predominant White presence reduces expectations that protests will be forcefully repressed. We complement these results with analysis of tens of thousands of images shared on social media during the 2020 BLM protests, finding a significant association between the presence of Whites in the images and user engagement and amplification. The findings suggest that allyship can be a powerful tool for promoting sociopolitical change amid deep structural inequality.

Correcting misperceptions of the other political party does not robustly reduce support for undemocratic practices or partisan violence.

A growing consensus suggests that a cause of support for undemocratic practices and partisan violence is that partisans misperceive the other side. That is, they vastly exaggerate the extent to which members of the other party support undemocratic practices and violence. When these misperceptions are corrected, citizens' own beliefs moderate. I present results from an experiment that show that misperception corrections do not have an effect in the presence of competing information (i.e., that challenges the validity of the correction or offers a conflicting narrative). Basic corrections do not constitute a robust way to counter democratic backsliding stemming from citizens' misperceptions. The results highlight the need to devise stronger misperception interventions and, more generally, to consider competing information environments when devising any scalable behavioral intervention.

Conflict, violence, and warfare among early farmers in Northwestern Europe.

Bioarchaeological evidence of interpersonal violence and early warfare presents important insights into conflict in past societies. This evidence is critical for understanding the motivations for violence and its effects on opposing and competing individuals and groups across time and space. Selecting the Neolithic of northwestern Europe as an area for study, the present paper examines the variation and societal context for the violence recorded in the human skeletal remains from this region as one of the most important elements of human welfare. Compiling data from various sources, it becomes apparent that violence was endemic in Neolithic Europe, sometimes reaching levels of intergroup hostilities that ended in the utter destruction of entire communities. While the precise comparative quantification of healed and unhealed trauma remains a fundamental problem, patterns emerge that see conflict likely fostered by increasing competition between settled and growing communities, e.g., for access to arable land for food production. The further development of contextual information is paramount in order to address hypotheses on the motivations, origins, and evolution of violence as based on the study of human remains, the most direct indicator for actual small- and large-scale violence.

Commemorating local victims of past atrocities and far-right support over time.

Does public remembrance of past atrocities lead to decreased support for far-right parties today? Initiatives commemorating past atrocities aim to make visible the victims and crimes committed against them. This runs counter to revisionist actors who attempt to downplay or deny atrocities and victims. Memorials for victims might complicate such attempts and reduce support for revisionist actors. Yet, little empirical evidence exists on whether that happens. In this study, we examine whether exposure to local memorials that commemorate victims of atrocities reduces support for a revisionist far-right party. Our empirical case is the Stolpersteine ("stumbling stones") memorial in Berlin, Germany. It commemorates victims and survivors of Nazi persecution in front of their last freely chosen place of residence. We employ time-series cross-sectional analyses and a discontinuity design using a panel dataset that matches the location and date of placement of new Stolpersteine with the election results from seven elections (2013 to 2021) at the level of polling station areas. We find that, on average, the presence of Stolpersteine is associated with a 0.96%-point decrease in the far-right vote share in the following election. Our study suggests that local memorials that make past atrocities visible have implications for political behavior in the present.

Cultural threat perceptions predict violent extremism via need for cognitive closure.

Understanding the psychological processes that drive violent extremism is a pressing global issue. Across six studies, we demonstrate that perceived cultural threats lead to violent extremism because they increase people's need for cognitive closure (NFC). In general population samples (from Denmark, Afghanistan, Pakistan, France, and an international sample) and a sample of former Mujahideen in Afghanistan, single-level and multilevel mediation analyses revealed that NFC mediated the association between perceived cultural threats and violent extremist outcomes. Further, in comparisons between the sample of former Afghan Mujahideen and the general population sample from Afghanistan following the known-group paradigm, the former Mujahideen scored significantly higher on cultural threat, NFC, and violent extremist outcomes. Moreover, the proposed model successfully differentiated former Afghan Mujahideen participants from the general Afghan participants. Next, two preregistered experiments provided causal support for the model. Experimentally manipulating the predictor (cultural threat) in Pakistan led to higher scores on the mediator (NFC) and dependent variables (violent extremist outcomes). Finally, an experiment conducted in France demonstrated the causal effect of the mediator (NFC) on violent extremist outcomes. Two internal meta-analyses using state-of-the-art methods (i.e., meta-analytic structural equation modeling and pooled indirect effects analyses) further demonstrated the robustness of our results across the different extremist outcomes, designs, populations, and settings. Cultural threat perceptions seem to drive violent extremism by eliciting a need for cognitive closure.

Hate crime supporters are found across age, gender, and income groups and are susceptible to violent political appeals.

Hate crime is a pervasive problem across societies. Though perpetrators represent a small share of the population, their actions continue in part because they enjoy community support. But we know very little about this wider community of support; existing surveys do not measure whether citizens approve of hate crime. Focusing on Germany, where antiminority violence is entrenched, this paper uses original surveys to provide systematic evidence on the nature and impacts of hate crime support. Employing direct and indirect measures, I find that significant shares of the population support antirefugee hate crime and that the profile of supporters is broad, going much beyond common perpetrator types. I next use a candidate choice experiment to show that this support has disturbing political consequences: among radical right voters, hate crime supporters prefer candidates who endorse using gun violence against refugees. I conclude that a significant number of citizens empower potential perpetrators from the bottom-up and further legitimize hate crime from the top-down by championing violence-promoting political elites.

Evaluating the impact of a street outreach intervention on participant involvement in gun violence.

The past several years have witnessed increased calls for community violence interventions (CVIs) that address firearm violence while centering local expertise and avoiding the criminal legal system. Currently, little evidence exists on CVI effectiveness at the individual level. This study presents an evaluation of the impact of a street outreach-based CVI [Chicago CRED (Create Real Economic Destiny)] on participant involvement in violence. We used a quasiexperimental design with a treatment sample of 324 men recruited by outreach staff from 2016 to 2021 and a balanced comparison sample of 2,500 men from a network of individuals arrested in CRED's service areas. We conducted a Bayesian survival analysis to evaluate CRED's effect on individual violence-related outcomes on three levels of treatment: All enrolled participants, a subsample that made it through the initial phase, and those who completed programming. The intervention had a strong favorable effect on the probability of arrest for a violent crime for those completing the program: After 24 mo, CRED alumni experienced an 11.3 percentage point increase in survival rates of arrest for a violent crime relative to their comparisons (or, stated differently, a 73.4% reduction in violent crime arrests). The other two treatment levels experienced nontrivial declines in arrests but did not reach statistical significance. No statistically significant reduction in victimization risk was detected for any of the treatment levels. Results demonstrate that completion of violence intervention programming reduces the likelihood of criminal legal involvement for participants, despite the numerous systemic and environmental factors that impede personal success.

Impaired striatal glutamate/GABA regulation in violent offenders with antisocial personality disorder and psychopathy.

Men with antisocial personality disorder (ASPD) with or without psychopathy (+/-P) are responsible for most violent crime in society. Development of effective treatments is hindered by poor understanding of the neurochemical underpinnings of the condition. Men with ASPD with and without psychopathy demonstrate impulsive decision-making, associated with striatal abnormalities in functional neuroimaging studies. However, to date, no study has directly examined the potential neurochemical underpinnings of such abnormalities. We therefore investigated striatal glutamate: GABA ratio using Magnetic Resonance Spectroscopy in 30 violent offenders (16 ASPD-P, 14 ASPD + P) and 21 healthy non-offenders. Men with ASPD +/- P had a significant reduction in striatal glutamate : GABA ratio compared to non-offenders. We report, for the first time, striatal Glutamate/GABA dysregulation in ASPD +/- P, and discuss how this may be related to core behavioral abnormalities in the disorders.

Lung Disease and Social Justice: Chronic Obstructive Pulmonary Disease as a Manifestation of Structural Violence.

Lung health, the development of lung disease, and how well a person with lung disease is able to live all depend on a wide range of societal factors. These systemic factors that adversely affect people and cause injustice can be thought of as "structural violence." To make the causal processes relating to chronic obstructive pulmonary disease (COPD) more apparent, and the responsibility to interrupt or alleviate them clearer, we have developed a taxonomy to describe this. It contains five domains: 1) avoidable lung harms (processes impacting lung development, processes that disadvantage lung health in particular groups across the life course), 2) diagnostic delay (healthcare factors; norms and attitudes that mean COPD is not diagnosed in a timely way, denying people with COPD effective treatment), 3) inadequate COPD care (ways in which the provision of care for people with COPD falls short of what is needed to ensure they are able to enjoy the best possible health, considered as healthcare resource allocation and norms and attitudes influencing clinical practice), 4) low status of COPD (ways COPD as a condition and people with COPD are held in less regard and considered less of a priority than other comparable health problems), and 5) lack of support (factors that make living with COPD more difficult than it should be, i.e., socioenvironmental factors and factors that promote social isolation). This model has relevance for policymakers, healthcare professionals, and the public as an educational resource to change clinical practices and priorities and stimulate advocacy and activism with the goal of the elimination of COPD.

Protest movements involving limited violence can sometimes be effective: Evidence from the 2020 BlackLivesMatter protests.

SignificanceThe effects of recent protests for racial equality, particularly when they included violence, are currently of public and academic interest. To better understand these effects, we combine a dataset of all 2020 BlackLivesMatter protests with survey data containing measures of prejudice and support for police reform. Protests were not associated with reductions in prejudice, but were associated with increases in support for police reform. Specifically, a mix of nonviolent and violent protests was associated with an increase in police-reform support among conservatives living in liberal areas. This study highlights the importance of considering multiple measures of protest effectiveness and suggests that mass protest (including when it mixes nonviolence and violence) can be effective at advancing the movement's goals.

A comparison of political violence by left-wing, right-wing, and Islamist extremists in the United States and the world.

Although political violence has been perpetrated on behalf of a wide range of political ideologies, it is unclear whether there are systematic differences between ideologies in the use of violence to pursue a political cause. Prior research on this topic is scarce and mostly restricted to self-reported measures or less extreme forms of political aggression. Moreover, it has generally focused on respondents in Western countries and has been limited to either comparisons of the supporters of left-wing and right-wing causes or examinations of only Islamist extremism. In this research we address these gaps by comparing the use of political violence by left-wing, right-wing, and Islamist extremists in the United States and worldwide using two unique datasets that cover real-world examples of politically motivated, violent behaviors. Across both datasets, we find that radical acts perpetrated by individuals associated with left-wing causes are less likely to be violent. In the United States, we find no difference between the level of violence perpetrated by right-wing and Islamist extremists. However, differences in violence emerge on the global level, with Islamist extremists being more likely than right-wing extremists to engage in more violent acts.

Correcting inaccurate metaperceptions reduces Americans' support for partisan violence.

Scholars, policy makers, and the general public have expressed growing concern about the possibility of large-scale political violence in the United States. Prior research substantiates these worries, as studies reveal that many American partisans support the use of violence against rival partisans. Here, we propose that support for partisan violence is based in part on greatly exaggerated perceptions of rival partisans' support for violence. We also predict that correcting these inaccurate "metaperceptions" can reduce partisans' own support for partisan violence. We test these hypotheses in a series of preregistered, nationally representative, correlational, longitudinal, and experimental studies (total n = 4,741) collected both before and after the 2020 US presidential election and the 2021 US Capitol attack. In Studies 1 and 2, we found that both Democrats' and Republicans' perceptions of their rival partisans' support for violence and willingness to engage in violence were very inaccurate, with estimates ranging from 245 to 442% higher than actual levels. Further, we found that a brief, informational correction of these misperceptions reduced support for violence by 34% (Study 3) and willingness to engage in violence by 44% (Study 4). In the latter study, a follow-up survey revealed that the correction continued to significantly reduce support for violence approximately 1 mo later. Together, these results suggest that support for partisan violence in the United States stems in part from systematic overestimations of rival partisans' support for violence and that correcting these misperceptions can durably reduce support for partisan violence in the mass public.

Integrating topic modeling and word embedding to characterize violent deaths.

SignificanceWe introduce an approach to identify latent topics in large-scale text data. Our approach integrates two prominent methods of computational text analysis: topic modeling and word embedding. We apply our approach to written narratives of violent death (e.g., suicides and homicides) in the National Violent Death Reporting System (NVDRS). Many of our topics reveal aspects of violent death not captured in existing classification schemes. We also extract gender bias in the topics themselves (e.g., a topic about long guns is particularly masculine). Our findings suggest new lines of research that could contribute to reducing suicides or homicides. Our methods are broadly applicable to text data and can unlock similar information in other administrative databases.

Current research overstates American support for political violence.

SignificanceRecent political events show that members of extreme political groups support partisan violence, and survey evidence supposedly shows widespread public support. We show, however, that, after accounting for survey-based measurement error, support for partisan violence is far more limited. Prior estimates overstate support for political violence because of random responding by disengaged respondents and because of a reliance on hypothetical questions about violence in general instead of questions on specific acts of political violence. These same issues also cause the magnitude of the relationship between previously identified correlates and partisan violence to be overstated. As policy makers consider interventions designed to dampen support for violence, our results provide critical information about the magnitude of the problem.

Climate change-induced population pressure drives high rates of lethal violence in the Prehispanic central Andes.

Understanding the influence of climate change and population pressure on human conflict remains a critically important topic in the social sciences. Long-term records that evaluate these dynamics across multiple centuries and outside the range of modern climatic variation are especially capable of elucidating the relative effect of­and the interaction between­climate and demography. This is crucial given that climate change may structure population growth and carrying capacity, while both climate and population influence per capita resource availability. This study couples paleoclimatic and demographic data with osteological evaluations of lethal trauma from 149 directly accelerator mass spectrometry 14C-dated individuals from the Nasca highland region of Peru. Multiple local and supraregional precipitation proxies are combined with a summed probability distribution of 149 14C dates to estimate population dynamics during a 700-y study window. Counter to previous findings, our analysis reveals a precipitous increase in violent deaths associated with a period of productive and stable climate, but volatile population dynamics. We conclude that favorable local climate conditions fostered population growth that put pressure on the marginal and highly circumscribed resource base, resulting in violent resource competition that manifested in over 450 y of internecine warfare. These findings help support a general theory of intergroup violence, indicating that relative resource scarcity­whether driven by reduced resource abundance or increased competition­can lead to violence in subsistence societies when the outcome is lower per capita resource availability.

Reforming the police through procedural justice training: A multicity randomized trial at crime hot spots.

SignificanceOur study is a randomized trial in policing confirming that intensive training in procedural justice (PJ) can lead to more procedurally just behavior and less disrespectful treatment of people at high-crime places. The fact that the PJ intervention reduced arrests by police officers, positively influenced residents' perceptions of police harassment and violence, and also reduced crime provides important guidance for police reform in a period of strong criticism of policing. This randomized trial points to the potential for PJ training not simply to encourage fair and respectful policing but also to improve evaluations of the police and crime prevention effectiveness.