The effects of eye position and expectation on sound localization

Ss who are exposed to a sound coming from straight ahead, but who turn their eyes 20 deg to the side toward a visible speaker during the exposure period and expect to hear the sound coming from the visible source, show a shift in localization of the sound up to a maximum of about 9 deg. Ss who only turn their eyes 20 deg to the side during the exposure period show a smaller but significant shift in sound localization, while Ss who do not turn their eyes, but are led to expect that the sound will appear to come from a visible loudspeaker 20 deg to the side, show no significant shift. Comparison of test results before and after the exposure period, with eyes directed straight ahead and no visible speaker present, shows the presence of a localization aftereffect for those experimental groups that showed a significant localization shift during the exposure period. Sounds are localized a few degrees to the side of their physical location in the same direction as the shift in localization during the exposure period. Further experiments show that part, but not all, of the shift in localization during the exposure period can be understood in terms of a shift in perceived head direction. The localization aftereffects are shown not to be due to change in physical or perceived eye or head position.