STIMULUS CLASSIFICATION PROCEDURE FOR ASSESSING THE EXTENT TO WHICH BINAURAL PROCESSING IS SPECTRALLY ANALYTIC OR SYNTHETIC

A two-dimensional stimulus classification paradigm was used to assess the extent to which listeners' processing of interaural delays at low frequencies is spectrally analytic or synthetic. Listeners were presen ted with a 753-Hz target with an interaural delay that varied from tri al to trial, taking on one of ten values, five leading to the left ear and five leading to the right. A 553-Hz distracter component was simu ltaneously presented, with its interaural delay also presented at one of ten different values. During a block of 100 trials, each of the pos sible combinations of target and distracter delay was presented once, and only once, in a random order. Listeners were instructed to make le ft-right judgments based on the target delay. Each condition was repea ted ten times, and the slopes of the best linear boundaries between le ft and right responses were used to derive the relative weights given to the target and distracter in judgments of laterality. Six of the ni ne listeners gave increasing weight to the target as the duration of t he signals was increased from 25 or 50 to 400 ms. Three listeners show ed little change with duration; one consistently gave equal weight to the target and distracter, two consistently gave greater weight to the target than to the distracter. The utility of classification paradigm s in the study of multidimensional acoustic signals is discussed.