Application of Cascade Theory to Online Systems: A Study of Email and Google Cascades

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Why do markets boom and crash? Why do fads and social norms start and end? The answer is found in a branch of social science literature called “cascade theory.” Cascade theory explains the observable human behavior of imitation: following the actions of someone else simply because one has observed that behavior, rather than following one’s own intuition. This article discusses cascade theory in the context of online systems, namely e-mail and Google. E-mail cascades parallel their offline cascade counterparts as information and misinformation is spread from person to person. However, e-mail cascades also exhibit an amplified herd effect and an amplified proliferation of the cascade itself. Google cascades are even more remarkable due to a unique compounding effect found in the ranking algorithm, which itself simultaneously follows and reinforces cascading behavior, something that is not seen in typical informational cascades.