Abstract
The Line Motion Illusion is characterised as illusory perception of a solid line appearing to grow away from a preceding visual or auditory cue. This illusion is attributed to the widening of spatial attention after attention has been narrowly captured to the cue's location. Although this illusion has been found using either visual or auditory cues (Shimojo, Miyauchi, & Hikosaka, 1997), it has yet to be examined under different crossmodal conditions where cues from different modalities may either enhance or compete in capturing attention when cues are spatially congruent or incongruent. Subjects' perception of the illusion was assessed under spatially congruent and incongruent crossmodal conditions using auditory and visual cues. In the congruent condition, the auditory cue (a short tone) and the visual cue (a flash) were both presented on the same side of the display (either left or right). In the incongruent condition, the cues were presented simultaneously on opposite sides. These crossmodal conditions were compared to unimodal conditions of only visual or auditory cues. We also manipulated the time interval between the presentation of cues and bar to assess the extent to which the illusion depended on the timing of the cues. Eye position was monitored via an SMI RED eye tracker to ensure they maintained fixation. Overall results show similarly high rates of reporting the illusion across all conditions (73-90%). However, in the incongruent crossmodal condition subjects reported the illusory motion from visual cues significantly more than the auditory cues. We also found the illusion depended on the relative timing between the cues and the bar. Our findings provide new insights into the extent to which visual and auditory cues compete in the putative capture of attention to produce the line motion illusion.
Meeting abstract presented at VSS 2018