title: Falling skyscrapers: when cross-modal perception of verticality fails.
abstract: The perception of verticality is critical for balance control and interaction with the world. But this complex process fails badly under certain circumstances-usually as the result of an illusion. Here, we report on a real-world example of how the brain fails to disregard body position on a moving mountain tram and adopts an inappropriate frame of reference, which prompts passengers to perceive skyscrapers leaning by as much as 30°. To elucidate the sensory origin of this misperception, we conducted field experiments on the moving tram to systematically disentangle the contributions of four sensory systems known to affect verticality perception, namely, vestibular, tactile, proprioceptive, and visual cues. Our results refute the intuitive assumption that the perceived tilt of the buildings is based on visual error signals and demonstrate instead that a unified percept of verticality is a product of the synergistic interaction among multiple sensory systems and the contextual information available in the real world.
authors.affiliation: Department of Psychology, The University of Hong Kong, Hong Kong. ch_tseng@alumni.uci.edu
authors.forename: Chia-Huei
authors.initials: CH
authors.lastname: Tseng
authors.forename: Hiu Mei
authors.initials: HM
authors.lastname: Chow
authors.forename: Lothar
authors.initials: L
authors.lastname: Spillmann
mesh_terms: D000328:Adult; D000368:Aged; D003463:Cues; D018466:Gravity Sensing / Q000502:physiology*; D006801:Humans; D007088:Illusions / Q000502:physiology*; D008875:Middle Aged; D010465:Perception; D011187:Posture; D011434:Proprioception / Q000502:physiology*; D013028:Space Perception / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: cognitive processes; perception