Abstract:
It was observed that the perceptual lateralization of a sound (test) having an interaural time difference (ITD) is shifted away from that of a prior sound (adapter) having a different ITD. First, the frequency selectivity of this ``auditory lateralization aftereffect'' was examined for sinusoids presented through headphones, with various combinations of adapter and test frequencies below 800 Hz, using the method of constant stimuli. The magnitude of the aftereffect was found to be largest when the frequencies of the two sounds were similar. It decreased as the frequency difference increased, and virtually disappeared at a frequency difference of one-half octave. Second, the ITD selectivity of the aftereffect was examined for 400-Hz tones. Subjects' judgments of lateralization were measured directly in terms of the azimuth of the test signal for various combinations of adapter and test ITDs in the range of (plus or minus)625 (mu)s. It was found that the magnitude of the aftereffect was rather small when the ITDs of the adapter and test signal were similar, and was largest when ITDs differed by 250 or 375 (mu)s. These results will be discussed in terms of implications for theories of binaural interaction, possible neural sites, and functional roles of the effects.