Milena Tsvetkova

London School of Economics and Political Science | LSE · Department of Methodology

Disagreement and conflict are a fact of social life and considerably affect our well-being and productivity. Such negative interactions are rarely explicitly declared and recorded and this makes them hard for scientists to study. We overcome this challenge by investigating the patterns in the timing and configuration of contributions to a large onl...

Segregation is widespread in all realms of human society. Several influential studies have argued that intolerance is not a prerequisite for a segregated society, and that segregation can arise even when people generally prefer diversity. We investigated this paradox experimentally, by letting groups of high-school students play four different real...

Previous research has shown that reciprocity can be contagious when there is no option to repay the benefactor and the recipient instead channels repayment toward strangers. In this study, we test whether retaliation can also be contagious. Extending previous work on “paying it forward,” we tested two mechanisms for the social contagion of antisoci...

Why do people help strangers when there is a low probability that help will be directly reciprocated or socially rewarded? A possible explanation is that these acts are contagious: those who receive or observe help from a stranger become more likely to help others. We test two mechanisms for the social contagion of generosity among strangers: gener...

Most people dislike inequality, yet large disparities in income and wealth remain remarkably high in many democratic countries. One possible explanation is that people's social networks affect their perception of inequality and consequently, their demands for redistribution. In this study, we investigate the effects of assortativity by wealth (obse...

Integrative experiment design promises to foster cumulative knowledge by changing how we design experiments, build theories, and conduct research. I support the push to increase commensurability across experimental research but raise several reservations regarding results-driven and large-team-based research. I argue that it is vital to preserve ac...

Mechanisms of social control reinforce norms that appear harmful or wasteful, such as mutilation practises or extensive body tattoos. We suggest such norms arise to serve as signals that distinguish between ingroup ‘friends' and outgroup ‘foes', facilitating parochial cooperation. Combining insights from research on signalling and parochial coopera...

Inequality prevails in science. Individual inequality means that most perish quickly and only a few are successful, while gender inequality implies that there are differences in achievements for women and men. Using large-scale bibliographic data and following a computational approach, we study the evolution of individual and gender inequality for...

Mechanisms of social control reinforce norms that appear harmful or wasteful, such as mutilation practices or extensive body tattoos. We suggest such norms arise to serve as signals that distinguish between ingroup “friends” and outgroup “foes”, facilitating parochial cooperation. Combining insights from research on signalling and parochial coopera...

Humans and other intelligent agents often rely on collective decision making based on an intuition that groups outperform individuals. However, at present, we lack a complete theoretical understanding of when groups perform better. Here, we examine performance in collective decision making in the context of a real-world citizen science task environ...

People differ in intelligence, cognitive ability, personality traits, motivation, and similar valued and, to a large degree, inherited characteristics that determine success and achievements. When does individual heterogeneity lead to a fair distribution of rewards and outcomes? Here, we develop this question theoretically and then test it experime...

Rankings and leaderboards are often used in crowdsourcing contests and online communities to motivate individual contributions but feedback based on social comparison can also have negative effects. Here, we study the unequal effects of such feedback on individual effort and performance for individuals of different ability. We hypothesize that the...

The rise of social media and computational social science (CSS) has opened countless opportunities to explore social science questions with new forms of data and methods. However, CSS research on socioeconomic inequality, a fundamental problem in sociology, has been constrained due to the lack of individual-level socioeconomic status (SES) measures...

Antisocial behavior can be contagious, spreading from individual to individual and rippling through social networks. Moreover, it can spread not only through third-party influence from observation, just like innovations or individual behavior do, but also through direct experience, via “pay-it-forward” retaliation. Here, we distinguish between the...

The standard experimental paradigm in the social, behavioral, and economic sciences is extremely limited. Although recent advances in digital technologies and crowdsourcing services allow individual experiments to be deployed and run faster than in traditional physical labs, a majority of experiments still focus on one-off results that do not gener...

In the last several decades, ample evidence from across evolutionary biology, behavioural economics and econophysics has solidified our knowledge that reputation can promote cooperation across different contexts and environments. Higher levels of cooperation entail higher final payoffs on average, but how are these payoffs distributed among individ...

Collective decision-making is ubiquitous when observing the behavior of intelligent agents, including humans. However, there are inconsistencies in our theoretical understanding of whether there is a collective advantage from interacting with group members of varying levels of competence in solving problems of varying complexity. Moreover, most exi...

Ranking in contests and competitions is often used to motivate individual contributions but it can have negative impact on the group. Here, we study the effect of social comparison on the dispersion and predictability of individual performance. We hypothesize that the effects of social comparison on effort will differ for top-performers and bottom-...

Antisocial behavior such as negative gossip, cheating, or bullying can be contagious, spreading from individual to individual and rippling through social networks. Previous experimental research has suggested that individuals who either experience or observe antisocial behavior become more likely to behave antisocially. Here, we distinguish between...

There are few research studies focusing on how humans can better understand segregation using mathematical models. In this paper, we explore how upper secondary school students work with the Schelling model using a computer game that was purposely designed for this study. The students were then allowed to run the model themselves. The results show...

Our upbringing and education influence not only how we present and distinguish ourselves in the social world but also how we perceive others. We apply this central sociological idea to the social media context. We conduct a large-scale online study to investigate whether observers can correctly guess the education of others from their Facebook prof...

From small communities to entire nations and society at large, inequality in wealth, social status, and power is one of the most pervasive and tenacious features of the social world. What causes inequality to emerge and persist? In this study, we investigate how the structure and rules of our interactions can increase inequality in social groups. S...

Z-scores for network assortativity by wealth for fixed and strategically rewired networks from a subset of the experiments on (A) network structure, (B) network fluidity, and (C) reputation tracking. The z-score shows to what extent the observed assortativity by wealth for each experimental condition deviates from what we expect to see in a network...

The relationship between individual use of punishment and individual wealth in the treatment conditions with punishment. In each plot, values for individuals in the same interaction group are shown with the same symbol. The figure also shows fitted lines and estimates from ordinary least-square regressions (standardized regression coefficient, equi...

Z-scores for network assortativity by cooperativeness for fixed and strategically rewired networks from a subset of the experiments on (A) network structure, (B) network fluidity, and (C) reputation tracking. The z-score shows to what extent the observed assortativity by cooperativeness for each experimental condition deviates from what we expect t...

The relationship between group average wealth and group inequality in the experiments on network structure and network fluidity. The figure shows fitted lines and estimates from ordinary least-square regressions (standardized regression coefficient, equivalent to the Pearson correlation, on top and p-value on bottom, with asterisk if p < 0.05). The...

The relationship between group average wealth and group inequality in the experiments on reputation and punishment. The figure shows fitted lines and estimates from ordinary least-square regressions (standardized regression coefficient, equivalent to the Pearson correlation, on top and p-value on bottom, with asterisk if p < 0.05). The standard err...

The relationship between individual cooperativeness and individual wealth in the conditions from the experiments on network structure. In each plot, values for individuals in the same interaction group are shown with the same symbol. The figure also shows fitted curves and estimates from ordinary least-square regressions (standardized regression co...

The relationship between individual cooperativeness and individual wealth in the conditions from the experiments on network fluidity. In each plot, values for individuals in the same interaction group are shown with the same symbol. The figure also shows fitted curves and estimates from ordinary least-square regressions (standardized regression coe...

The relationship between individual cooperativeness and individual wealth in the conditions from the experiments on network fluidity. In each plot, values for individuals in the same interaction group are shown with the same symbol. The figure also shows fitted curves and estimates from ordinary least-square regressions (standardized regression coe...

The relationship between individual use of punishment and individual cooperativeness in the treatment conditions with punishment. In each plot, values for individuals in the same interaction group are shown with the same symbol. The figure also shows fitted lines and estimates from ordinary least-square regressions (standardized regression coeffici...

In recent years, there has been a huge increase in the number of bots online, varying from Web crawlers for search engines, to chatbots for online customer service, spambots on social media, and content-editing bots in online collaboration communities. The online world has turned into an ecosystem of bots. However, our knowledge of how these automa...

The number of bots, the number of edits by bots, and the proportion of edits done by bots between 2001 and 2010. Between 2003 and 2008 the number of bots and their activity have been increasing. This trend, however, appears to have subsided after 2008, suggesting that the system may have stabilized. (TIFF)

Bots reciprocate much more than humans do also at a smaller timescale. We measure reciprocity as the proportion of observed turning points out of all possible. (A) A significant proportion of bot-bot interactions have intermediate or high values of reciprocity. (B) The majority of human-human interactions are not reciprocated. (TIFF)

Four types of interaction trajectories suggested by the k-means analysis. The left panels show a sample of the trajectories, including bot-bot and human-human interactions and trajectories from all languages. The right panels show the distribution of latency, imbalance, and reciprocity for each type of trajectory. The three properties measure the a...

Descriptive statistics for the bot-bot layer and the human-human layer in the multi-layer networks of reverts. Bots revert each other to a great extent. They also reciprocate each other’s reverts to a considerable extent. Their interactions are not as clustered as for human editors. Still, both for bots and humans, more senior editors tend to rever...

The number of articles with a certain number of bot-bot and human-human reverts. (A) Few articles include more than 10 bot-bot reverts. The most contested articles tend to be about foreign countries and personalities. Further, the same articles also re-appear in different languages. (B) There are many articles that are highly contested by humans. T...

Performance of the k-means clustering algorithm for different number of clusters and for sub-samples with different minimum length of trajectories. (A) The elbow method requires the smallest k that most significantly reduces the sum of squared errors for the clustering. Here, the method suggests that four clusters give the best clustering of the da...

For the majority of languages, bots are mainly reverted by other bots, as opposed to human editors or vandals. English and the Romance languages in our data present exceptions, with less than 20% of bot reverts are done by other bots. (TIFF)

Bot-bot interactions are on average more balanced than human-human interactions. We define imbalance as the final proportion of reverts between i and j that were not reciprocated. (A) A significant proportion of bot-bot interactions have low imbalance. (B) The majority of human-human interactions are perfectly unbalanced. (TIFF)

Bot-bot interactions have different characteristic time scale than human-human interactions. The figures show the distribution of interactions for a particular latency, where we define latency as the mean log time in seconds between successive reverts. (A) Bot-bot interactions have a characteristic latency of 1 month, as indicated by the peak in th...

In recent years, there has been a huge increase in the number of bots online, varying from Web crawlers for search engines, to chatbots for online customer service, spambots on social media, and content-editing bots in online collaboration communities. The online world has turned into an ecosystem of bots. However, our knowledge of how these automa...

Recently developed information communication technologies, particularly the Internet, have affected how we, both as individuals and as a society, create, store, and recall information. Internet also provides us with a great opportunity to study memory using transactional large scale data, in a quantitative framework similar to the practice in stati...

Recently developed information communication technologies, particularly the Internet, have affected how we, both as individuals and as a society, create, store, and recall information. Internet also provides us with a great opportunity to study memory using transactional large scale data, in a quantitative framework similar to the practice in stati...

In the HUMANE research project, we aim to support analysis of, and design for human‐machine networks. Towards this end, we have developed a HUMANE typology and method. The typology serves to characterize human‐machine networks on dimensions pertaining to the level of agency in the actors of the network, the strength of the relations between the act...

Researchers have used Wikipedia data as a source to quantify attention on the web. One way to do it is by analysing the editorial activities and visitors' views of a set of Wikipedia articles. In this paper, we particularly study attention to aircraft incidents and accidents using Wikipedia in two different language editions, English and Spanish. W...

The Internet not only has changed the dynamics of our collective attention, but also through the transactional log of online activities, provides us with the opportunity to study attention dynamics at scale. In this paper, we particularly study attention to aircraft incidents and accidents using Wikipedia transactional data in two different languag...

In this paper we outline an initial typology and framework for the purpose of profiling human-machine networks, that is, collective structures where humans and machines interact to produce synergistic effects. Profiling a human-machine network along the dimensions of the typology is intended to facilitate access to relevant design knowledge and exp...

In this paper we outline an initial typology and framework for the purpose of profiling human-machine networks, that is, collective structures where humans and machines interact to produce synergistic effects. Profiling a human-machine network along the dimensions of the typology is intended to facilitate access to relevant design knowledge and exp...

Disagreement and conflict are a fact of social life and considerably affect our well-being and productivity. Such negative interactions are rarely explicitly declared and recorded and this makes them hard for scientists to study. We overcome this challenge by investigating the patterns in the timing and configuration of contributions to a large onl...

In the current hyper-connected era, modern Information and Communication Technology systems form sophisticated networks where not only do people interact with other people, but also machines take an increasingly visible and participatory role. Such human-machine networks (HMNs) are embedded in the daily lives of people, both or personal and profess...

Design for human-machine networks is challenging. To improve our understanding of human-machine networks and strengthen the design of such networks and supporting technologies, a first version of the HUMANE typology and method has been developed. The typology is based on a systematic literature review (HUMANE D1.1), and is structured according to f...

Every day, millions of people write online restaurant reviews, leave product ratings, provide answers to an unknown user’s question, or contribute lines of code to open-source software, all without any direct reward or recognition. People help strangers offline as well, as when people anonymously donate blood or stop to help a stranded motorist, bu...

The outsourcing of domestic tasks is an important strategy for coping with the competing time claims of the family and the workplace. Previous research explained the use of domestic help mainly in terms of financial and time constraints. In this article, we conceptualize household work as producing not only goods but also direct utility, and we arg...

Noise is widely regarded as a residual category—the unexplained variance in a linear model or the random disturbance of a predictable pattern. Accordingly, formal models often impose the simplifying assumption that the world is noise-free and social dynamics are deterministic. Where noise is assigned causal importance, it is often assumed to be a s...

We present a model of social interaction in which actors choose their partners and play the Chicken Game with them. In contrast to most previous models of the coevolution of games and networks, we assume that the actors can employ different actions against different partners. This allows us to derive two different solutions to the coordination and...

The outsourcing of domestic tasks is an important strategy for coping with the competing time claims of the family and the workplace. Previous research explained the use of domestic help mainly in terms of financial and time constraints. In this article, we conceptualize household work as producing not only goods but also direct utility, and we arg...

In this article, we develop a simple model for the effect of gossip spread on social network structure. We define gossip as information passed between two individuals A and B about a third individual C which affects the strengths of all three relationships: it strengthens A-B and weakens both B-C and A-C. We find, in both an analytic derivation and...

Asymmetric relations such as lending money, doing favors and giving advice form the basis of mutual aid and cooperation in human societies. However, they also provide a mechanism for the emergence of inequalities and hierarchies. Reciprocal behavior at the dyadic and network levels can prevent the aggregation of unequal exchange into unfair macro-l...