Factors in the discrimination of tonal patterns. III. Frequency discrimination with components of well-learned...

Estimates of the effectiveness of selective auditory attention were obtained by adjusting the level of a target tone, which was presented as one 40-msec component in a ten-tone sequential pattern. When the levels of target and nontarget tones were the same, frequency-discrimination thresholds (delta f/f) following prolonged training varied from 0.01-0.02 for minimal-uncertainty testing conditions to 0.1-0.2 under high trial-to-trial stimulus uncertainty. The functions relating frequency discrimination to target-tone level are widely separated for the two conditions; comparing them, we conclude that the effects of selective auditory attention can be equated to a 50-dB variation in signal level. Patterns that had been well-learned during the minimal-stimulus (remembered standard) procedure. The results of these latter experiments are consistent with a "top-down" processing interpretation in which well-learned patterns are first identified to locate the portions requiring further resolution.