The ability to discriminate a change in frequency was measured in 2IFC, same‐different, and yes–no paradigms using two tasks commom in the literature—discrimination of two pure tones differing only in frequency and detection of frequency modulation(FM). In the pure‐tone task, differences in the level of frequency‐discrimination performance as a function of paradigm were similar to those previously observed for both frequency and intensity discrimination. The level of performance in 2IFC and same–different exceeded the level of performance in yes–no by more than the theory of signal detection would predict. For the FM detection data, differences in the level of performance between paradigms were less than the theory of signal detection would predict. These differences increased, however, when the same subjects were tested in a task requiring discrimination of two FMtones. These results suggest that a memory factor is operating in discrimination tasks to a greater degree than in detection tasks. The memory factor is interpreted in terms of criterion variance. Subject Classification: 65.54, 65.35, 65.75.