The ability of human listeners to localize sound sources can be measured by discrimination experiments, such as the minimum audible angle (MAA) paradigm, or by source identification experiments. In principle, these two kinds of experiments can be unified by a statistical decision theory model, incorporating a process whereby a sensory scale is referenced to an absolute scale. To test this idea we performed several kinds of free field discrimination and source identification experiments, both in the light and in the dark. Among our conclusions are the following: (1) The variance of the referencing process depends upon the width of the absolute scale required by the experiment. It doubles as the width increases from 2°–33°. (2) The MAA experiment, nominally a measurement of discrimination, probably includes a source identification component as well. In fact, our data in the light are consistent with a model in which the MAA experiment is treated exclusively as a source identification task. [Work supported by the NIH and NIMH.]