A regional systems approach has become a mainstay for examining intersocietal interaction in the prehistoric Southwest, although problems with the approach exist. Particularly problematic for the model is how smaller-scale societies might have interacted with larger-scale societies. As a case study in comprehending areas in between, I examine the Animas phase (about A.D. 1150-1450), located in extreme southeastern Arizona, southwestern New Mexico, and northeastern Sonora. Considerable controversy exists over the relationship between Animas phase sites and the much more imposing remains found at and near Paquimé (Casas Grandes) in northwestern Chihuahua. This debate is explored through two contrasting theories about smaller-scale societies: (1) that they are relatively stable and autonomous remnants of older social systems or (2) that they are dependent peripheries marginalized by core areas. Neither of the models appears to adequately explain the mosaic of features that the Animas phase possesses. A more dynamic model is proposed that recognizes the presence of regional interaction, the low efficiency and high costs of interactión for the prehistoric Southwest, and the sources of power of small-scale social systems.