Evidence for Crossmodal Interactions across Depth on Target Localisation Performance in a Spatial Array

Auditory stimuli are known to improve visual target recognition and detection when both are presented in the same spatial location. However, most studies have focused on crossmodal spatial congruency along the horizontal plane and the effects of audio-visual spatial congruency in depth (ie along the depth axis) are relatively less well understood. In the following experiments we presented a visual (face) or auditory (voice) target stimulus in a location on a spatial array which was either spatially congruent or incongruent in depth (ie positioned directly in front or behind) with a crossmodal stimulus. The participant's task was to determine whether a visual (experiments 1 and 3) or auditory (experiment 2) target was located in the foreground or background of this array. We found that both visual and auditory targets were less accurately located when crossmodal stimuli were presented from different, compared to congruent, locations in depth. Moreover, this effect was particularly found for visual targets located in the periphery, although spatial incongruency affected the location of auditory targets across both locations. The relative distance of the array to the observer did not seem to modulate this congruency effect (experiment 3). Our results add to the growing evidence for multisensory influences on search performance and extend these findings to the localisation of targets in the depth plane.