The coadsorption of Na with CO and O on Ni(111) is studied by high-resolution electron energy loss spectroscopy. Experimental evidence for a very short-range interaction between Na and coadsorbates is reported, in contrast with recent theoretical predictions overestimating nonlocal alkali-induced effects. Loss spectra show distinct features, as a consequence of different local [CO]:[Na] and [O]:[Na] stoichiometries.