Audiotactile interactions beyond the space and body parts around the head.

Recent research has reported that spatial modulation effects of audiotactile interactions tend to be limited to the space and body parts around the head. The present study investigated the generality of this finding by manipulating body parts stimulated and spatial relationships between the body parts and sounds. In Experiment 1, tactile stimuli were presented randomly to either left or right cheek, hand (palm or back) placed near the head, and knee while auditory stimuli were presented to either the same or opposite side from loudspeakers close to the head. Participants made speeded spatial discrimination responses regarding the side (left versus right) of the tactile stimulation. For any body part stimulated, the performance was worse when the auditory stimuli were presented from the opposite side rather than from the same side. Experiment 2 demonstrated that the spatial modulation effects for the palm or the back of the hand occurred irrespective of hand position (near or far from the head) and sound position (near or far from the head). The sounds delivered from near the head exerted a greater influence on tactile spatial discrimination performance as compared with the sound delivered from far from the head. Furthermore, the back of the hand was more influenced by the auditory stimuli than the palm when the hands were placed near the sounds. These results suggest that the spatial modulation effects of audiotactile interactions can occur beyond the space and body surface around the head.