  Non-standard scenarios described by effective interactions can manifest
themselves indirectly, via corrections to the Standard Model cross sections. It
should be desirable to identify at a given confidence level the source of such
deviations among the different possible explanations. We here discuss the
identification reach on gravity in extra dimensions from the four-fermion
compositeness-inspired contact interactions and viceversa, using as basic
observable the differential cross section of $e^+e^-\to\bar{f}f$ at the ILC,
and emphasize the role of beams polarization in enhancing the identification
sensitivity.
