Predictive Ability of the Auditory System during Smooth and Abrupt Movements of Low-Intensity Sound Images

The predictive ability of the human auditory system in locating the positions of the end points of movement trajectories was studied in comparison with stationary fused sound sources. Sound images moved smoothly or abruptly from the midline of the head towards one of the ears. Sound source movement was created by altering interaural stimulus time differences. The perceived positions of the end points of movement trajectories, like the positions of stationary sound images, depended on the final interaural time delay. With final interaural time delays of less than 200 μsec, the movement end points of sound images were displaced further from the midline of the head relative to the position of the corresponding stationary sound images; at delays of greater than 400 μsec, they were closer. The resulting anticipatory displacement can be regarded as a manifestation of the predictive ability of the auditory system in locating moving sound images. For smoothly moving sound images with interaural delays of greater than 400 μsec, longer-lasting stimuli were found to induce greater displacement of end points than those with shorter stimuli.