Barba's (2012) article deftly weaves three main themes in one argument about operant variability. From general theoretical considerations on operant behavior (Catania, 1973), Barba derives methodological guidelines about response differentiation and applies them to the study of operant variability. In the process, he uncovers unnoticed features of operant variability research (e.g., Neuringer, 2002) and proposes interesting modifications and extensions of current experimental practices. Barba's article calls for renewed attention to important issues, and the authors find merit in his proposal to evaluate operant variability by comparing response distributions along a common continuous measure. The authors are less convinced, however, by the conceptual underpinnings that he brings to the task. (Contains 1 figure and 1 footnote.)