Projects

“creating-critical-mass-98x98" Creating Critical Mass

Active

The “tipping point” is a common explanation for sudden shifts in collective behavior, but the limitations of historical evidence and conflicting theoretical models present a challenge to understanding how a small but committed group can change the behavior of an entire population. On the one hand, economic theories emphasize strategic choice and suggest that established conventions are highly stable. On the other hand, a popular physics model emphasizes the dynamics of individual interactions, predicting that a group with just 10% of the population can initiate social change, but does not for account individual preferences to conform to the majority.


data-science-98x98 Networked Innovation

Active

Do efficient communication networks increase innovation? Scientists, engineers and strategists all work within highly connected environments where each person’s solutions are used to inspire and inform the work of others. The communication networks between researchers can determine the rate at which new ideas and innovations reach the rest of the community, giving rise to better solutions to difficult problems. As the complexity of the problem increases, so does the putative need for more efficient collaboration networks.


collective-intelligence-98x98 Collective Intelligence

Active

Decentralized networks offer enormous potential for crowd-sourced information aggregation, whether it takes the form of emergent market forces or a deliberative organizational process. In 1907, Sir Francis Galton observed that a large number of individual beliefs can produce highly accurate opinions when averaged. Even when no one person knows the right solution, independent errors cancel each other out, and groups as a whole can produce answers with pinpoint accuracy. The challenge with harnessing such statistical power is that when people communicate, they learn from each other, and in turn adjust their beliefs based on information circulating in the network.


NDG-square-birthcontrol Birth Control Connect

Active

This project evaluates women’s attitudes about birth control. We conduct a randomized controlled trial to examine whether anonymous online discussion with women who use intrauterine devices (IUDs) as their method of birth control can change the attitudes toward IUDs among women who have never used IUDs. The intervention is an anonymous online community, in which non-IUD users are assigned either into 9-person groups with other non-IUD users or 9-person groups with 4 IUD users. The study will observe attitude changes among non-IUD users within these groups.


ineq-img-sq.jpg Durable Inequality

Active

Do reduced barriers to social exchange create more durable forms of inequality? We investigate this puzzle with a simple model of pairwise bargaining in populations stuck in states of inter-group inequality. This model builds on previous work suggesting populations should reach stable states of equality given infinite time. We consider the implications of both increasing the number of interacting groups, and varying the structure of interaction networks.


NDG-square-cancertwitter Preventing Cervical Cancer With Twitter

Active

This project studies the discussion of HPV vaccination and cervical cancer on social media. Cervical cancer causes 4,220 annual deaths. 17% women do not receive appropriate Pap smear screening. Only 35% of girls 13 to 17 fully receive HPV vaccine. Unfortunately physician based recommendation approaches miss many women. However, social media is used extensively – especially by young women. Using a mixed methods approach combining machine learning, qualitative analysis, and experimental manipulations. We will analyze Twitter discussion to determine how social media messages can most effectively be used to promote HPV vaccination and cervical cancer screenings.


Support or Competition?

2016

Online social networks have become a highly attractive target for large scale health initiatives; however, there is insufficient knowledge about why online networks might be effective sources of social influence for improving physical activity levels. In a randomized controlled trial, we evaluate the effects of social support and social comparison independently, and in combination, to determine how social motivations for behavior change directly impact people’s exercise activity.


NDG-square-originsofnetworks Origins of Networks

2015

Recent research on social contagion has demonstrated significant effects of network topology on the dynamics of diffusion. However, network topologies are not given a priori. Rather, they are patterns of relations that emerge from individual and structural features of society, such as population composition, group heterogeneity, homophily, and social consolidation.


NDG-square-pennshape Shape UP

2015

Sedentary lifestyle is an escalating national and global epidemic that has commanded increasing attention from health care professionals and social scientists. Paradoxically, the advent of the Internet and social media may be both an explanatory factor in this epidemic, and a potential solution.


norms99 Emergence of Social Norms

2015

How do norms emerge? In small groups, people have complete knowledge of one another’s behaviors, making it relatively easy to create shared expectations. In larger groups, reaching a consensus or convention on basic behaviors such as how to greet one another, which side of the road to drive on, and what constitutes a “fair” bargaining outcome, can be established by top down, authoritative decree. However, most examples of large-scale patterns of social coordination do not rely upon global control, nor can they always assume common knowledge among all members of a group, or pre-existing cultural “focal points” that will provide familiar references for social self-organization.


ohc-98x98 Network Evolution

2013

How do online health networks evolve? A growing number of online health communities offer individuals the opportunity to receive information, advice, and support from their peers. Our recent studies have demonstrated that these new online contacts can be important informational resources, and can even exert significant influence on individuals’ behavior in various contexts. However little is known about how people select their health contacts in these virtual domains. This is because selection preferences in peer networks are notoriously difficult to detect. In existing networks, unobserved pressures on tie formation—such as common organizational memberships, introductions by friends of friends, or limitations on accessibility—may mistakenly be interpreted as individual preferences for interacting/not interacting with others.


Simple Model of Stability Stability in Critical Mass Dynamics

2013

Collective behaviors often spread via the self-reinforcing dynamics of critical mass. In collective behaviors with strongly self-reinforcing dynamics, incentives to participate increase with the number of participants, such that incentives are highest when the full population has adopted the behavior. By contrast, when collective behaviors have weakly self-reinforcing dynamics, incentives to participate “peak out” early, leaving a residual fraction of non-participants. In systems of collective action, this residual fraction constitutes free riders, who enjoy the collective good without contributing anything themselves.


NDG-square-homophilycriticalmass Homophily, Networks, & Critical Mass

2013

Formal theories of collective action face the problem that in large groups a single actor makes such a small impact on the collective good that cooperation is irrational. Critical mass theorists argue that this ‘large group problem’ can be solved by an initial critical mass of contributors, whose efforts can produce a ‘bandwagon’ effect, making cooperation rational for the remaining members of the population.


NDG-square-diffusinghealth Diffusing Health Innovations

2011

How does the composition of a population affect the adoption of health behaviors and innovations? To understand how changes in people’s social “neighborhoods” affect the spread of health innovations, we developed an in vivo study that manipulated the level of “homophily”—similarity of social contacts—among the participants in an online fitness program.


NDG-square-scalefreefailure Scale Free Failure

2009

A class of inhomogenously wired networks called “scale-free” networks have been shown to be more robust against failure than more homogenously connected exponential networks. However, for “complex contagions,” such as social movements, collective behaviors, and cultural and social norms, multiple reinforcing ties are needed to support the spread of a behavior diffusion. Scale-free networks are much less robust than exponential networks for the spread of complex contagions, which highlights the value of more homogenously distributed social networks for the robust transmission of collective behavior.


NDG-square-spreadingbehavioronine Spreading Behavior Online

2009

How do behaviors spread through social networks? Harnessing the new opportunity offered by social media, our research pioneered the use of online technologies to investigate the effects of social structure on the spread of health behaviors. Using experimentally controlled online health communities, we recruited over 1,500 people to join a health website, called “The Healthy Lifestyle Network,” in which participants were embedded into anonymous, Internet-based networks. Once participants joined the study, they were randomized into one of two network conditions – one community was designed with tightly clustered, “strong tie” networks, and one was designed with randomly structured “weak tie” or “small world” networks.


NDG-square-_complexcontagions Complex Contagions

2007

The strength of weak ties is that they tend to be long—they connect socially distant locations, allowing information to diffuse rapidly. The authors test whether this “strength of weak ties” generalizes from simple to complex contagions. Complex contagions require social affirmation from multiple sources. Results show that as adoption thresholds increase, long ties can impede diffusion.


NDG-square-culturaldrift Cultural Drift

2007

Studies of cultural differentiation have shown that social mechanisms that normally lead to cultural convergence—homophily and influence—can also explain how distinct cultural groups can form. However, this emergent cultural diversity has proven to be unstable in the face of cultural drift—small errors or innovations that allow cultures to change from within.


NDG-square-emperorsdilemma The Emperor’s Dilemma

2005

The authors demonstrate the uses of agent-based computational models in an application to a social enigma they call the “emperor’s dilemma,” based on the Hans Christian Andersen fable. In this model, agents must decide whether to comply with and enforce a norm that is supported by a few fanatics and opposed by the vast majority. They find that cascades of self-reinforcing support for a highly unpopular norm cannot occur in a fully connected social network.