ASA 127th Meeting M.I.T. 1994 June 6-10

4pPP14. Preliminary measures of the focusing of attention on auditory streams.

Marie-Claire Botte

Carolyn Drake

Renaud Brochard

Stephen McAdams

Anne-Marie Argenti

Perception Auditive, Lab. de Psychol. Exp., CNRS URA 316), Universite Rene Descartes, EPHE, 28 rue Serpente, F-75006, Paris, France

The focusing of attention on an auditory stream was studied by asking subjects to detect a temporal irregularity in the interonset interval between two successive tones of a regular sequence in a 2AFC procedure. Eight subjects heard the sequence with the irregularity presented concomitantly with two other regular sequences, each sequence having its own specific tempo, number, and frequency of tones. One of these sequences, presented alone as a cue for the target, preceded two observation intervals 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 nontarget sequences. Increasing the level of a probe sequence above the level of both the target and the other nontarget sequences resulted in a significant improvement in detection for five subjects. Detection performance in the probe sequence was equivalent to that in the target sequence when the probe level was increased by 18 dB. For the three other subjects, detection in the probe sequence remained at chance, whatever its level. Therefore, the ``attenuation'' of unattended auditory streams can attain as much as 18 dB for some subjects, probably being higher for others.