Conspiracy theories play a troubling role in political discourse, yet the motivations of conspiracy endorsers can be obscure to outsiders. Online forums provide a valuable window into the day-to-day discourse of conspiracy theorizing, but one that is difficult to quantify. We used non-negative matrix factorization to create a topic model of the r/conspiracy forum on Reddit.com. This subreddit provides a large and unique corpus which spans many years and numerous authors. We show that within the forum, there are multiple sub-populations distinguishable by their topic loading. Further, these differences are readily interpretable as differences in background beliefs and motivations. These groups regularly interact with one another by commenting; hence topic modeling reveals subgroups that would not be revealed by simple network analyses. The diversity of the distinct subgroups places constraints on theories of what generates conspiracy theorizing: neither simple irrationality nor common preoccupations of topics seem to fit the bill. Instead, we suggest, conspiracy theorizing seems to be primarily driven by higher-order preoccupations with evidence and argument, along with rhetorical strategies which allow diverse groups to each address any particular theme.
Automatic annotation of histopathological images using a latent topic model based on non-negative matrix factorization
