Influence of eye fixation on the effects of visual and auditory cuing in sound localization
Be�ta Tomoriov�1, Rudolf Andoga1, Norbert Kopčo1,2
1 Perception and Cognition Lab, Technical University of Ko�ice, Slovakia,
2 Dept. of Cognitive and Neural Systems, Boston University and
Center for Cognitive Neuroscience, Duke University
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Experiments were performed to examine the influence of auditory and visual cuing on horizontal sound localization in virtual environment. Subjects localized a transient auditory stimulus originating in the frontal horizontal plane. In most runs, the stimuli were preceded by a cue predicting (correctly or incorrectly) the hemisphere (left or right) from which the subsequent target arrived. Subjects were instructed to focus their attention to the side indicated by the cue. The cue could be either visual or auditory, and the cue-to-target onset asynchrony ranged from 400 to 1600 ms.
Results from the first experiment showed that both visual and auditory cuing biased the perceived location of the stimuli [Kopco, Tomoriova, Andoga, �Visual and auditory hemispheric cuing in horizontal sound localization�, J. Acoust. Soc. Am, 2007]. However, since the listeners� eyes were not fixated, the effects could be influenced by eye movements. In the current study, the same experiment was performed except that eyes were now fixating to the center of the display to eliminate this influence.
Results show a negligible effect of eye fixation on the bias caused by the visual cue, and a much much stronger effect of fixation on the bias caused by the auditory cue: Specifically, when the eyes were not fixated, the auditory cue biased the perceived locations towards the medial plane. With the eyes fixated, this bias almost disappeared. These results suggest that fixating the eyes reduces the listeners� ability to focus their attention on the side indicated by a cue, in particular when the cue is auditory. This reduction is probably caused by an interference between the task of fixating the center of the display and the task of reorienting attention towards the side of the cue.
[Supported by the Slovak Science Grant Agency.]