  Culturomics was recently introduced as the application of high-throughput
data collection and analysis to the study of human culture. Here we make use of
this data by investigating fluctuations in yearly usage frequencies of specific
words that describe social and natural phenomena, as derived from books that
were published over the course of the past two centuries. We show that the
determination of the Hurst parameter by means of fractal analysis provides
fundamental insights into the nature of long-range correlations contained in
the culturomic trajectories, and by doing so, offers new interpretations as to
what might be the main driving forces behind the examined phenomena. Quite
remarkably, we find that social and natural phenomena are governed by
fundamentally different processes. While natural phenomena have properties that
are typical for processes with persistent long-range correlations, social
phenomena are better described as nonstationary, on-off intermittent, or Levy
walk processes.
