Discrimination of pure tones after a variable time delay was investigated using an ABX procedure. Three experiments were performed. In the first, scores for subjects were near perfect (>90%) for systematically increasing delays between B and X of up to 120 sec when A and B were equal‐amplitude pure tones of 1000 and 1100 Hz, respectively. In the second and third experiments, three tone pairs were employed having frequency spacings of 10% and 2%, respectively. The pair used, the order within pairs, and the order in which variable delays were presented were all randomized. In these experiments, scores fell abruptly after a delay of 20 sec for the 10% spacing and after 5 sec for the 2% spacing. The superior discrimination of Expt. 1 is attributed to learning.

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