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Kyle Cassidy

Creating Critical Mass

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.

Cervical Cancer Prevention with Twitter

This project seeks to understand 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.

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Check here for the latest papers, publications and information about the Network Dynamics Group.

The Emperor’s Dilemma

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.

Cultural Drift

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.

Scale Free Failure

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.

Network Evolution

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.

Diffusing Health 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.

Homophily, networks, and critical mass

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.

A simple model of stability in critical mass dynamics

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.

Emergence of Spontaneous Social Norms

How do norms emerge? In small groups, people have complete knowledge of one another’s behaviors, making it relatively easy to create shared expectations.

Networked Innovation

Do efficient communication networks increase collective intelligence? 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.

Collective Intelligence

Decentralized networks offer enormous potential for crowd-sourced information aggregation, whether it takes the form of emergent market forces or a deliberative organizational process.

Birth Control Connect

Exposure to women using a novel method of contraception has the potential to influence contraceptive beliefs, and ultimately an individual’s decision to use contraception.


Sedentary lifestyle is an escalating national and global epidemic that has commanded increasing attention from health care professionals and social scientists.

Origins of Networks

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.

Complex Contagions

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.

Spreading Behavior Online

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.