The effect of frequency cueing on the perceptual segregation of simultaneous tones: Bottom-up and top-down contributions.

Listeners were presented with two simultaneous tones of different frequencies (more than one octave apart) and asked to identify the tone that was amplitude-modulated while a tonal precursor was presented to cue the frequency of the lower frequency tone. Performance thresholds were estimated based on the duration of the tone-pair. In Exp. I the duration of the precursor varied from 100 to 400 ms and the inter-stimulus interval (ISI) between the precursor and the tone-pair varied from 0 to 1 s. The presence of the precursor facilitated segregation. As the ISI increased, the facilitation effect of the precursor increased for the precursor durations of 100 and 200 ms, but not for the 400-ms precursor duration. When the precursor was presented to the contralateral ear relative to the tone-pair in Exp. II, no significant change to the precursor effect was observed. These observations contradict the predictions of the model based solely on bottom-up processing, suggesting the likely involvement of top-down processes.