Fluorescence anisotropy decay measurements were performed to determine the temperature and composition dependence of the local dynamics of each component of a miscible blend of high molecular weight polyisoprene (PI) and polyvinylethylene (PVE). The local dynamics of each component over the entire composition range from PI:PVE 0:100-100:0 was examined over the temperature range 20-100 degrees C. Optical measurements of the local dynamics of a probe chain in a matrix which is similar to 100% the second polymer species are reported for the first time. Two blending rules for the temperature and composition dependence of the component dynamics are proposed, and their suitability to describe the observed local component dynamics is assessed. Different blending rules were found to be appropriate for the different blend components. A comparison to the work of Gisser and Ediger, describing solvent modification in polymer solutions, is also performed. The relative time scale of the motions of the two polymers in the blend is found to be Linked to the rate at which the incorporation of a polymer additive influences the dynamics of the host polymer.