  We present a self-contained discussion of the universality classes of the
generalized epidemic process (GEP) on Poisson random networks, which is a
simple model of social contagions with cooperative effects. These effects lead
to rich phase transitional behaviors that include continuous and discontinuous
transitions with tricriticality in between. With the help of a comprehensive
finite-size scaling theory, we numerically confirm static and dynamic scaling
behaviors of the GEP near continuous phase transitions and at tricriticality,
which verifies the field-theoretical results of previous studies. We also
propose a proper criterion for the discontinuous transition line, which is
shown to coincide with the bond percolation threshold.
