Reviewed by
Elizabeth Hunter
Dublin Institute of Technology
Complex Spreading Phenomena in Social Systems provides an overview of the field of complex contagions. Complex contagions are contagions where transmission requires reinforcement from multiple contacts; opposed to simple contagions that only require one contact for transmission. This book takes on the job of defining why it is necessary to study complex contagions as their own entity and develop new methods that deviate from those used for simple contagions.Many of the topics introduced in the book are extremely relevant in today’s world such as misinformation spreading on social media; learning how to study these contagions and differentiate them from more simple contagions can prove useful in many areas. Understanding how information and memes go viral and how information spreads during an emergency can provide better ways to get important information distributed to as many people as possible and help to stop the spread of misinformation.
The book also introduces us to the difficulties of studying complex contagions. Unlike a simple contagion, there are issues such as homophily, shared environments, and dependence and these factors need to be taken into consideration when determining if someone adopts an idea or behavior. The introduction first presents this problems and potential solutions and they are discussed in many of the chapters later in the book.
The book is broken down into four sections: Introduction, Models and Theories, Observational Studies, and Controlled Studies. The introduction starts with a literature review on the topic of complex contagions and discusses applications, advances in the field and directions for future work. It introduces readers to Granovetter’s work, one of the earliest studies on network dynamics and network diffusion. Granovetter is referenced throughout the text in many different chapters and most of the models and studies discussed are influenced or motivated by Granovetter. Readers are then given a chapter introducing them to modeling complex contagions and the contagion condition and finally a chapter on the challenges of using observational data. While the introduction provides an overview of the topic and a base for readers to continue on into the more complex topics in later chapters, it leaves readers wondering what is to come and how the topics in the introduction relate to the rest of the book. The editors write the last chapter as a conclusion of the whole work, however, the book could significantly benefit from an introductory text from the editors that maps out the topics in the book and relates the topics to each other.
The modeling section stars with a generalized model that can be used for both disease like and social like spreading behaviors. The next two chapters take similar models and add complexity, discussing message passing and optimal modularity. The final two move in a different direction, discussing how to analyze empirical datasets by simulating spreading phenomena and theories for how to identify influencers in networks. Combining real data with models these two chapters serve as a bridge between the Models and Theories section and the Observational Studies section.
The Observational Studies section of the book is the most relevant section where complex contagions are related to hot topics in today’s world and this section is where the idea of why studying complex contagions is important is really driven home to the readers. Included in the section are chapters on misinformation spreading on Facebook, the effects of bots on information diffusion, and information spreading during emergencies. These topics all feel highly relevant in today’s society and the section shows how complex contagions relate to these topics.
The Controlled Studies section concludes the book: it begins with a chapter that discusses randomized experiments, then two chapters that discuss actual experiments and then is finished with a conclusion by the editors. The section importantly provides details of real experiments, the experimental design and discussions of how researchers controlled for factors such as homophily that are present in the observational studies. While the flow of the section is much improved from having a more general Randomized Experiments chapter before the chapters with experiments it deviates from the previous sections in that it includes a generalized overview section and does not just jump straight into models or observational studies.
Overall the book provides a wide overview of the field, not simply focusing on the models of complex contagions or theory but also including observational studies and controlled studies. It leaves the reader with a better understanding of complex contagions, the importance of studying complex contagions, and the difficulties of studying complex contagions and also serves as a good introduction to the field. However, at times it feels as if the chapters have no relation to the one before or after. Some models and topics are reintroduced in multiple chapters and at times there is little flow from one chapter to the next. This is a short fall that comes from both the ambitious overview of topic of complex contagions the book takes on and the style of book where each chapter is written by a different set of authors.
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