  Effective equations often provide powerful tools to develop a systematic
understanding of detailed properties of a quantum system. This is especially
helpful in quantum cosmology where several conceptual and technical
difficulties associated with the full quantum equations can be avoided in this
way. Here, effective equations for Wheeler-DeWitt and loop quantizations of
spatially flat, isotropic cosmological models sourced by a massive or
interacting scalar are derived and studied. The resulting systems are
remarkably different from that given for a free, massless scalar. This has
implications for the coherence of evolving states and the realization of a
bounce in loop quantum cosmology.
