  Social reinforcement and modular structure are two salient features observed
in the spreading of behavior through social contacts. In order to investigate
the interplay between these two features, we study the generalized epidemic
process on modular networks with equal-sized finite communities and adjustable
modularity. Using the analytical approach originally applied to clique-based
random networks, we show that the system exhibits a bond-percolation type
continuous phase transition for weak social reinforcement, whereas a
discontinuous phase transition occurs for sufficiently strong social
reinforcement. Our findings are numerically verified using the finite-size
scaling analysis and the crossings of the bimodality coefficient.
