A probe-signal study of auditory discrimination of complex tones

The present experiments used an analogue of the probe-signal method of Greenberg and Larkin [J. Acoust. Soc. Am. 44, 1513-1523 (1968)] to investigate the extent to which listeners direct attention to a particular spectral region when discriminating complex tones. The listeners' task was to discriminate between two seven-component complex tones on the basis of an increment in the level of a single component. On two-thirds of trials the increment was achieved by adding a fixed primary signal to one component of the complex. The primary-signal trials were relatively easy and were intended to cue listeners to attend to the component to which the primary was added. On the remaining trials a smaller probe signal was added either to the cued component, or to one of three other components. The results of the first experiment, in which the complex tones had a flat spectrum, showed significantly better performance for probe signals applied to the cued component compared to the other three components. To control for the possibility that the observed pattern of results was due to the use of timbral cues, a second experiment was conducted in which the spectral profile of the tones was randomized between trials. The results for the second experiment were similar to those of the first experiment and are consistent with the idea that listeners were focusing attention on the spectral region defined by the primary signal.