INFLUENCE OF ACOUSTIC CONTEXT ON SOUND LOCALIZATION - AN AUDITORY ROELOFS EFFECT

The Roelofs effect is a visual direction illusion: if a large rectangu lar frame is seen offset from the straight-ahead direction, a small ta rget presented simultaneously is mislocalized in the opposite directio n. To investigate whether a similar context illusion might affect audi tory localization, we presented a ''frame'' of 6 speakers driven with a 300-Hz square wave, 30 degrees left or right of center. The ''target '' was a speaker driven with the same waveform, with the two sources i n random phase relationship. The target was mislocalized in a directio n opposite the frame, an auditory Roelofs effect. A second experiment, using dissimilar sounds for frame and target, yielded no frame-depend ent mislocalizations. The effect appeared both in verbal position esti mation, a measure of cognitive localization, and in open-loop pointing , a measure of localization in a sensorimotor system. We conclude that audition possesses only one representation of space, in contrast to t he two (cognitive and sensorimotor) of vision, The auditory representa tion corresponds most closely to vision's cognitive system.