Focalisation attentionnelle appliquée aux flux auditifs. Premières mesures

Abstract
The focalization of attention on an auditory stream was studied by asking subjects to detect a temporal irregularity in the onset interval between two tones of a regular sequence in a 2AFC procedure. Eight subjects heard the sequence with the irregularity in the presence of two other regular sequences, each of these three sequences having its specific tempo, number and frequency of tones. One of these sequences was presented alone as a cue for the target preceding two observation intervals, each containing the three concurrent sequences. The size of the irregularity detected at a 90% level in a target sequence was only detected at chance level in both non-target sequences. Increasing the level of a probe sequence above the level of both the target and the other non-target sequence resulted in a significant improvement of the detection 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 three other subjects, the detection in the probe remained at chance level whatever the probe level. Therefore, the attenuation of unattended auditory streams can attain as much as 18 dB, at least for some subjects.