Discriminating the direction of auditory motion

Abstract

Dichotic click trains presented through headphones were used to simulate changes in the interaural delay produced by a source moving horizontally in space. The interaural time-difference (ITD) in each click was increased by a constant ΔITD relative to the click immediately preceding it. Left motion was simulated with delays favoring the left ear and visa versa. The d’s for direction measured in a single interval design were linearly related to the number of clicks in the train and, by definition, the extent of change in ITD from first click to last. In experiment II, the middle clicks were eliminated; leaving only the first and last clicks. Performance was essentially unchanged, suggesting that subjects relied on only the onset–offset position of the moving image in experiment I. To examine this hypothesis, experiment III presented a variety of conditions for the middle clicks. If motion detection were simply based on the onset and offset of the total stimulus, then the interaural configuration of the middle clicks should be inconsequential. It was not. These results are explained in terms peripheral adaptation and an integration time of about 65 ms [Work supported by NIH.]