  A beam of light, reflected at a planar interface, does not follow perfectly
the ray optics prediction. Diffractive corrections lead to beam shifts; either
the reflected beam is displaced (spatial shift) and/or travels in a different
direction (angular shift), as compared to geometric optics. How does the degree
of spatial coherence of light influence these shifts? Theoretically, this has
turned out to be a controversial issue. Here we resolve the controversy
experimentally; we show that the degree of spatial coherence influences the
angular beam shifts, while the spatial beam shifts are unaffected.
