ATTENTIONAL FOCUSING APPLIED TO AUDITORY STREAMS - PRELIMINARY MEASUREMENTS

The focalization of attention on an auditory stream was studied by ask ing subjects to detect a temporal irregularity in the onset interval b etween two tones of a regular sequence in a 2AFC procedure. Eight subj ects heard the sequence with the irregularity in the presence of two o ther regular sequences, each of these three sequences having its speci fic tempo, number and frequency of tones. One of these sequences was p resented alone as a cue for the target preceding two observation inter vals, each containing the three concurrent sequences. The size of the irregularity detected at a 90% level in a target sequence was only det ected at chance level in both non-target sequences. Increasing the lev el of a probe sequence above the level of both the target and the othe r non-target sequence resulted in a significant improvement of the det ection for five subjects. The detection in the probe was equivalent to that in the target for a 18-dB increase of the probe level. For the t hree other subjects, the detection in the probe remained at chance lev el whatever the probe level. Therefore, the attenuation of unattended auditory streams can attain as much as 18 dB, at least for some subjec ts.