On the DL for Frequency

Abstract

Difference limens (DL) for 3 frequencies (250, 1000, and 4000 c.p.s.) were detd. for 2 trained observers by 2 psychophysical methods. In the 1st method (AX), the subject is presented a standard tone followed by a test tone; he judges whether the test tone is higher or lower than the standard. In the 2nd method (ABX), the subject decides whether the 3rd in a series of 3 tones sounds more like the 1st or the 2nd of the series. Though the 2 observers differ considerably in sensitivity, their DLs for the AX procedure are less than half the DLs for the ABX procedure. Comparison of these data with data in the literature on DLs for frequency indicates a wide range of values for different psychophysical procedures and for different subjects. Some observations reported illustrate the effect of such factors as practice and ensemble of stimulus conditions upon size of the DL. The influence of the stimulus ensemble upon judgement time is discussed briefly. In view of all exptl. data, it would be rather imprudent to postulate a "true" DL, or to infer the behavior of the peripheral organ from the size of DL measured under a given set of conditions. While there is undoubtedly some relation between the size of the DL and the so-called channel capacity, there is little reason to assume that the relation is a particularly simple one, given the different operations by means of which these 2 quantities are detd.