Critical Parameters of Spatial Diffusion Processes

The variety of outcomes of spatial diffusion processes-for example, "hierarchical" versus "contagious" spread, total versus partial saturation, and logistic versus other patterns of acceptance over time-makes it tempting to propose a multiplicity of processes. In this paper, however, the contrary hypothesis is tested, namely that the variability of observed outcomes can be generated by essentially one simple diffusion processthe difference in values of certain critical