Instability and violence in Imperial Rome: A "laboratory" for studying social contagion?

Imperial Rome with its >50% assassination rate of emperors, many of whom are depicted in history as ‘deranged’, initially appears a chaotic period of history beyond the purview of science. But time series analysis indicates this violence occurred non-randomly: reign length was autocorrelated and demonstrated ‘memory persistence,’ and short reigns occurred in clusters. Additionally, deviations from average reign-length occurred in patterns matching the Empire's rise and decline. A model is proposed for how army-backed usurpation and post-coup instability likely generated the observed cycles. The five-century span of Imperial Rome likely makes it the longest-lived regime with fair documentation, and potentially provides a ‘laboratory’ with ongoing relevance for studying transmission of violence and instability. © 2016 Wiley Periodicals, Inc. Complexity, 2016