The misperception of length in vision, haptics and audition

Participants felt, saw and heard stimuli travel over predetermined distances in three orientations – gravitational-vertical, radial and horizontal. On all trials participants were required to judge the length of the distance travelled. Judgments based on visual information over-estimated length in the radial direction, while those based on haptic information overestimated length in the gravitational-vertical direction. Length estimates based on auditory information were similar across the three orientations. A combined modality condition using visual, haptic and auditory information mimicked the vision condition. Results are interpreted in light of the horizontal-vertical illusion