In the vector format, the area of overlap between two areas is the intersection. (intersect (analysis) tool in the toolbox. You can thus compute the intersection between the "minx range" and each other range, then you compute the area of the intersection in a new field using "calculate geometry" (not necessary with geodatabase). If you have several polygon, right-click on the area field and ask the statistics.
But if you talk about spatial analyst, I assume that you work with raster. Then you have a continuous field and the overlap is defined by the minimum of the two rasters. You can do this with cell statistics.
Another way to visualize your distributions is simply to use a difference between the two rasters. If you do A-B, negative value indicate that you have more B than A. You can do it with the raster calculator (map algebra).